/*
 * Copyright (c) 1998, 2021 Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2019 IBM Corporation. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle - initial API and implementation from Oracle TopLink
//     07/19/2011-2.2.1 Guy Pelletier
//       - 338812: ManyToMany mapping in aggregate object violate integrity constraint on deletion
//     04/09/2012-2.4 Guy Pelletier
//       - 374377: OrderBy with ElementCollection doesn't work
//     14/05/2012-2.4 Guy Pelletier
//       - 376603: Provide for table per tenant support for multitenant applications
//     30/05/2012-2.4 Guy Pelletier
//       - 354678: Temp classloader is still being used during metadata processing
//     08/01/2012-2.5 Chris Delahunt
//       - 371950: Metadata caching
//     06/03/2013-2.5.1 Guy Pelletier
//       - 402380: 3 jpa21/advanced tests failed on server with
//         "java.lang.NoClassDefFoundError: org/eclipse/persistence/testing/models/jpa21/advanced/enums/Gender"
package org.eclipse.persistence.mappings;

import java.beans.PropertyChangeEvent;
import java.security.AccessController;
import java.security.PrivilegedActionException;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.HashSet;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.Vector;

import org.eclipse.persistence.annotations.BatchFetchType;
import org.eclipse.persistence.descriptors.ClassDescriptor;
import org.eclipse.persistence.descriptors.TablePerMultitenantPolicy;
import org.eclipse.persistence.descriptors.changetracking.ChangeTracker;
import org.eclipse.persistence.descriptors.changetracking.CollectionChangeEvent;
import org.eclipse.persistence.exceptions.ConversionException;
import org.eclipse.persistence.exceptions.DatabaseException;
import org.eclipse.persistence.exceptions.DescriptorException;
import org.eclipse.persistence.exceptions.QueryException;
import org.eclipse.persistence.exceptions.ValidationException;
import org.eclipse.persistence.expressions.Expression;
import org.eclipse.persistence.expressions.ExpressionBuilder;
import org.eclipse.persistence.history.AsOfClause;
import org.eclipse.persistence.history.HistoryPolicy;
import org.eclipse.persistence.indirection.IndirectCollection;
import org.eclipse.persistence.indirection.IndirectList;
import org.eclipse.persistence.indirection.ValueHolder;
import org.eclipse.persistence.internal.databaseaccess.Platform;
import org.eclipse.persistence.internal.descriptors.DescriptorIterator;
import org.eclipse.persistence.internal.descriptors.ObjectBuilder;
import org.eclipse.persistence.internal.descriptors.changetracking.AttributeChangeListener;
import org.eclipse.persistence.internal.descriptors.changetracking.ObjectChangeListener;
import org.eclipse.persistence.internal.expressions.ForUpdateClause;
import org.eclipse.persistence.internal.expressions.ObjectExpression;
import org.eclipse.persistence.internal.expressions.SQLDeleteStatement;
import org.eclipse.persistence.internal.expressions.SQLInsertStatement;
import org.eclipse.persistence.internal.expressions.SQLSelectStatement;
import org.eclipse.persistence.internal.expressions.SQLUpdateStatement;
import org.eclipse.persistence.internal.expressions.TableExpression;
import org.eclipse.persistence.internal.helper.ConversionManager;
import org.eclipse.persistence.internal.helper.DatabaseField;
import org.eclipse.persistence.internal.helper.DatabaseTable;
import org.eclipse.persistence.internal.helper.Helper;
import org.eclipse.persistence.internal.helper.NonSynchronizedVector;
import org.eclipse.persistence.internal.identitymaps.CacheId;
import org.eclipse.persistence.internal.identitymaps.CacheKey;
import org.eclipse.persistence.internal.queries.ContainerPolicy;
import org.eclipse.persistence.internal.queries.JoinedAttributeManager;
import org.eclipse.persistence.internal.queries.OrderedListContainerPolicy;
import org.eclipse.persistence.internal.security.PrivilegedAccessHelper;
import org.eclipse.persistence.internal.security.PrivilegedClassForName;
import org.eclipse.persistence.internal.security.PrivilegedNewInstanceFromClass;
import org.eclipse.persistence.internal.sessions.AbstractRecord;
import org.eclipse.persistence.internal.sessions.AbstractSession;
import org.eclipse.persistence.internal.sessions.ChangeRecord;
import org.eclipse.persistence.internal.sessions.DirectCollectionChangeRecord;
import org.eclipse.persistence.internal.sessions.MergeManager;
import org.eclipse.persistence.internal.sessions.ObjectChangeSet;
import org.eclipse.persistence.internal.sessions.UnitOfWorkImpl;
import org.eclipse.persistence.internal.sessions.remote.ObjectDescriptor;
import org.eclipse.persistence.internal.sessions.remote.RemoteSessionController;
import org.eclipse.persistence.mappings.converters.Converter;
import org.eclipse.persistence.mappings.converters.ObjectTypeConverter;
import org.eclipse.persistence.mappings.converters.SerializedObjectConverter;
import org.eclipse.persistence.mappings.converters.TypeConversionConverter;
import org.eclipse.persistence.queries.DataModifyQuery;
import org.eclipse.persistence.queries.DataReadQuery;
import org.eclipse.persistence.queries.DatabaseQuery;
import org.eclipse.persistence.queries.DeleteObjectQuery;
import org.eclipse.persistence.queries.DirectReadQuery;
import org.eclipse.persistence.queries.ModifyQuery;
import org.eclipse.persistence.queries.ObjectBuildingQuery;
import org.eclipse.persistence.queries.ObjectLevelReadQuery;
import org.eclipse.persistence.queries.QueryByExamplePolicy;
import org.eclipse.persistence.queries.ReadAllQuery;
import org.eclipse.persistence.queries.ReadQuery;
import org.eclipse.persistence.queries.ReportQuery;
import org.eclipse.persistence.queries.WriteObjectQuery;
import org.eclipse.persistence.sessions.CopyGroup;
import org.eclipse.persistence.sessions.DatabaseRecord;
import org.eclipse.persistence.sessions.remote.DistributedSession;

/**
 * <p><b>Purpose</b>: This mapping is used to store a collection of simple types (String, Number, Date, etc.)
 * into a single table.  The table must store the value and a foreign key to the source object.
 * A converter can be used if the desired object type and the data type do not match.
 *
 * @see Converter
 * @see ObjectTypeConverter
 * @see TypeConversionConverter
 * @see SerializedObjectConverter
 *
 * @author Sati
 * @since TOPLink/Java 1.0
 *
 *     09/18/2009-2.0 Michael O'Brien
 *       - 266912: JPA 2.0 Metamodel API (part of the JSR-317 EJB 3.1 Criteria API)
 *         add support for passing BasicMap value type to MapAttributeImpl via new attributeClassification field
 */
public class DirectCollectionMapping extends CollectionMapping implements RelationalMapping {

    /** Used for data modification events. */
    protected static final String Delete = "delete";
    protected static final String Insert = "insert";
    protected static final String DeleteAll = "deleteAll";
    protected static final String DeleteAtIndex = "deleteAtIndex";
    protected static final String UpdateAtIndex = "updateAtIndex";

    /** Allows user defined conversion between the object value and the database value. */
    protected Converter valueConverter;
    protected String valueConverterClassName;

    protected List<Expression> orderByExpressions;

    /** Stores the reference table*/
    protected DatabaseTable referenceTable;

    /** The direct field name is converted and stored */
    protected DatabaseField directField;
    protected Vector<DatabaseField> sourceKeyFields;
    protected Vector<DatabaseField> referenceKeyFields;

    /** Used for insertion for m-m and dc, not used in 1-m. */
    protected DataModifyQuery insertQuery;

    /** Used for deletion when ChangeSets are used */
    protected ModifyQuery changeSetDeleteQuery;
    protected transient ModifyQuery changeSetDeleteNullQuery; // Bug 306075
    protected boolean hasCustomDeleteQuery;
    protected boolean hasCustomInsertQuery;
    protected HistoryPolicy historyPolicy;

    /** Used (only in case listOrderField != null) to delete object with particular orderFieldValue */
    protected ModifyQuery deleteAtIndexQuery;
    /** Used (only in case listOrderField != null) to update orderFieldValue of object with particular orderFieldValue */
    protected ModifyQuery updateAtIndexQuery;
    protected boolean hasCustomDeleteAtIndexQuery;
    protected boolean hasCustomUpdateAtIndexQuery;

    /**
     * @since Java Persistence API 2.0
     * Referenced by MapAttributeImpl to pick up the BasicMap value parameter type
     * To specify the conversion type
     * */
    protected transient Class attributeClassification;
    protected String attributeClassificationName;

    /**
     * PUBLIC:
     * Default constructor.
     */
    public DirectCollectionMapping() {
        this.insertQuery = new DataModifyQuery();
        this.orderByExpressions = new ArrayList<>();
        this.sourceKeyFields = org.eclipse.persistence.internal.helper.NonSynchronizedVector.newInstance(1);
        this.referenceKeyFields = org.eclipse.persistence.internal.helper.NonSynchronizedVector.newInstance(1);
        this.selectionQuery = new DirectReadQuery();
        this.hasCustomInsertQuery = false;
        this.isPrivateOwned = true;
        this.isListOrderFieldSupported = true;
    }

    /**
     * PUBLIC:
     * Provide ascending order support for this direct collection mapping.
     */
    public void addAscendingOrdering() {
        this.hasOrderBy = true;
        orderByExpressions.add(new ExpressionBuilder().getField(getDirectFieldName()).ascending());
    }

    /**
     * PUBLIC:
     * Provide descending order support for this direct collection mapping.
     */
    public void addDescendingOrdering() {
        this.hasOrderBy = true;
        orderByExpressions.add(new ExpressionBuilder().getField(getDirectFieldName()).descending());
    }

    /**
     * ADVANCED:
     * Used this method to add custom ordering expressions when fetching
     * the collection. This could be things like expressions using a functions
     * like UPPER or NULLS LAST etc.
     */
    public void addOrdering(Expression expression) {
        this.orderByExpressions.add(expression);
    }

    @Override
    public boolean isRelationalMapping() {
        return true;
    }

    /**
     * PUBLIC:
     * Return the converter on the mapping.
     * A converter can be used to convert between the direct collection's object value and database value.
     */
    public Converter getValueConverter() {
        return valueConverter;
    }

    /**
     * PUBLIC:
     * Set the converter on the mapping.
     * A converter can be used to convert between the direct collection's object value and database value.
     */
    public void setValueConverter(Converter valueConverter) {
        this.valueConverter = valueConverter;
    }

    /**
     * PUBLIC:
     * Set the converter class name on the mapping. Initialized in
     * convertClassNamesToClasses.
     * A converter can be used to convert between the direct collection's object value and database value.
     */
    public void setValueConverterClassName(String valueConverterClassName) {
        this.valueConverterClassName = valueConverterClassName;
    }

    /**
     * PUBLIC:
     * Add the reference key field.
     * This is used for composite reference keys.
     * This is the foreign key field in the direct table referencing the primary key of the source object.
     * Both the reference field and the source field that it references must be provided.
     */
    public void addReferenceKeyField(DatabaseField referenceForeignKeyField, DatabaseField sourcePrimaryKeyField) {
        getSourceKeyFields().addElement(sourcePrimaryKeyField);
        getReferenceKeyFields().addElement(referenceForeignKeyField);
    }

    /**
     * PUBLIC:
     * Add the name of the reference key field.
     * This is used for composite reference keys.
     * This is the foreign key field in the direct table referencing the primary key of the source object.
     * Both the reference field name and the name of the source field that it references must be provided.
     */
    public void addReferenceKeyFieldName(String referenceForeignKeyFieldName, String sourcePrimaryKeyFieldName) {
        addReferenceKeyField(new DatabaseField(referenceForeignKeyFieldName), new DatabaseField(sourcePrimaryKeyFieldName));
    }

    /**
     * INTERNAL:
     * Clone and prepare the selection query as a nested batch read query.
     * This is used for nested batch reading.
     */
    @Override
    public ReadQuery prepareNestedBatchQuery(ObjectLevelReadQuery query) {
        // For CR#2646-S.M.  In case of inheritance the descriptor to use may not be that
        // of the source query (the base class descriptor), but that of the subclass, if the
        // attribute is only of the subclass.  Thus in this case use the descriptor from the mapping.
        // Also: for Bug 5478648 - Do not switch the descriptor if the query's descriptor is an aggregate
        ClassDescriptor descriptorToUse = query.getDescriptor();
        if ((descriptorToUse != this.descriptor) && (!descriptorToUse.getMappings().contains(this)) && (!this.descriptor.isDescriptorTypeAggregate())) {
            descriptorToUse = this.descriptor;
        }
        DataReadQuery batchQuery = new DataReadQuery();
        batchQuery.setName(getAttributeName());
        // Join the query where clause with the mappings,
        // this will cause a join that should bring in all of the target objects.
        ExpressionBuilder builder;
        Expression originalSelectionCriteria = null;

        // 2612538 - the default size of Map (32) is appropriate
        Map<Expression, Expression> clonedExpressions = new IdentityHashMap<>();
        builder = new ExpressionBuilder();
        // For flashback.
        if (query.hasAsOfClause()) {
            builder.asOf(query.getAsOfClause());
        }
        Expression batchSelectionCriteria = null;

        // Build the batch query, either using joining, or an exist sub-select.
        BatchFetchType batchType = query.getBatchFetchPolicy().getType();
        if (this.batchFetchType != null) {
            batchType = this.batchFetchType;
        }
        if (batchType == BatchFetchType.EXISTS) {
            // Using a EXISTS sub-select (WHERE EXIST (<original-query> AND <mapping-join> AND <mapping-join>)
            ExpressionBuilder subBuilder = new ExpressionBuilder(descriptorToUse.getJavaClass());
            subBuilder.setQueryClassAndDescriptor(descriptorToUse.getJavaClass(), descriptorToUse);
            ReportQuery subQuery = new ReportQuery(descriptorToUse.getJavaClass(), subBuilder);
            subQuery.setDescriptor(descriptorToUse);
            subQuery.setShouldRetrieveFirstPrimaryKey(true);
            Expression subCriteria = subBuilder.twist(getSelectionCriteria(), builder);
            if (query.getSelectionCriteria() != null) {
                // For bug 2612567, any query can have batch attributes, so the
                // original selection criteria can be quite complex, with multiple
                // builders (i.e. for parallel selects).
                // Now uses cloneUsing(newBase) instead of rebuildOn(newBase).
                subCriteria = query.getSelectionCriteria().cloneUsing(subBuilder).and(subCriteria);
            }
            subQuery.setSelectionCriteria(subCriteria);
            batchSelectionCriteria = builder.exists(subQuery);
        } else if (batchType == BatchFetchType.IN) {
            // Using a IN with foreign key values (WHERE FK IN :QUERY_BATCH_PARAMETER)
            batchSelectionCriteria = buildBatchCriteria(builder, query);
        } else {
            // For 2729729 must clone the original selection criteria first,
            // otherwise the original query will be corrupted.
            if (query.getSelectionCriteria() != null) {
                originalSelectionCriteria = query.getSelectionCriteria().copiedVersionFrom(clonedExpressions);
                builder = originalSelectionCriteria.getBuilder();
            }

            // Using a join, (WHERE <orginal-query-criteria> AND <mapping-join>)
            if (this.selectionQuery.isReadAllQuery()) {
                batchSelectionCriteria = builder.twist(this.selectionQuery.getSelectionCriteria(), builder);
            } else {
                batchSelectionCriteria = builder.twist(this.selectionQuery.getSQLStatement().getWhereClause(), builder);
            }
            // For 2729729, rebuildOn is not needed as the base is still the same.
            if (originalSelectionCriteria != null) {
                batchSelectionCriteria = batchSelectionCriteria.and(originalSelectionCriteria);
            }
            if (descriptorToUse.getQueryManager().getAdditionalJoinExpression() != null) {
                batchSelectionCriteria = batchSelectionCriteria.and(query.getDescriptor().getQueryManager().getAdditionalJoinExpression().rebuildOn(builder));
            }
            if (this.historyPolicy != null) {
                if (query.getSession().getAsOfClause() != null) {
                    builder.asOf(query.getSession().getAsOfClause());
                } else if (builder.getAsOfClause() == null) {
                    builder.asOf(AsOfClause.NO_CLAUSE);
                }
                batchSelectionCriteria = batchSelectionCriteria.and(this.historyPolicy.additionalHistoryExpression(builder, builder));
            }
        }

        SQLSelectStatement batchStatement = new SQLSelectStatement();

        for (DatabaseField keyField : getReferenceKeyFields()) {
            batchStatement.addField(builder.getTable(this.referenceTable).getField(keyField));
        }

        batchStatement.addField(builder.getTable(this.referenceTable).getField(this.directField));
        batchStatement.setWhereClause(batchSelectionCriteria);
        batchQuery.setSQLStatement(batchStatement);
        this.containerPolicy.addAdditionalFieldsToQuery(batchQuery, getAdditionalFieldsBaseExpression(batchQuery));

        batchStatement.normalize(query.getSession(), descriptorToUse, clonedExpressions);

        return batchQuery;
    }

    /**
     * INTERNAL:
     * Clone and prepare the joined direct query.
     * Since direct-collection does not build objects a nest query is not required.
     */
    @Override
    public ObjectLevelReadQuery prepareNestedJoins(JoinedAttributeManager joinManager, ObjectBuildingQuery baseQuery, AbstractSession session) {
        return null;
    }

    /**
     * INTERNAL:
     * Return the value of the field from the row or a value holder on the query to obtain the object.
     */
    @Override
    protected Object valueFromRowInternalWithJoin(AbstractRecord row, JoinedAttributeManager joinManager, ObjectBuildingQuery sourceQuery, CacheKey parentCacheKey, AbstractSession executionSession, boolean isTargetProtected) throws DatabaseException {
        ContainerPolicy policy = getContainerPolicy();
        Object value = policy.containerInstance();
        ObjectBuilder objectBuilder = this.descriptor.getObjectBuilder();
        // Extract the primary key of the source object, to filter only the joined rows for that object.
        Object sourceKey = objectBuilder.extractPrimaryKeyFromRow(row, executionSession);
        // If the query was using joining, all of the result rows by primary key will have been computed.
        List<AbstractRecord> rows = joinManager.getDataResultsByPrimaryKey().get(sourceKey);
        // If no 1-m rows were fetch joined, then get the value normally,
        // this can occur with pagination where the last row may not be complete.
        if (rows == null) {
            return valueFromRowInternal(row, joinManager, sourceQuery, executionSession);
        }
        int size = rows.size();

        if(size > 0) {
            // A set of direct values must be maintained to avoid duplicates from multiple 1-m joins.
            Set directValues = new HashSet();

            ArrayList directValuesList = null;
            ArrayList<AbstractRecord> targetRows = null;
            boolean shouldAddAll = policy.shouldAddAll();
            if(shouldAddAll) {
                directValuesList = new ArrayList(size);
                targetRows = new ArrayList(size);
            }
            Converter valueConverter = getValueConverter();
            // indicates if collection contains null
            boolean containsNull = false;
            // For each rows, extract the target row and build the target object and add to the collection.
            for (int index = 0; index < size; index++) {
                AbstractRecord sourceRow = rows.get(index);
                AbstractRecord targetRow = sourceRow;
                // The field for many objects may be in the row,
                // so build the subpartion of the row through the computed values in the query,
                // this also helps the field indexing match.
                targetRow = trimRowForJoin(targetRow, joinManager, executionSession);
                // Partial object queries must select the primary key of the source and related objects.
                // If the target joined rows in null (outerjoin) means an empty collection.
                Object directValue = targetRow.get(this.directField);
                if (directValue == null) {
                    if (size == 1) {
                        // A null direct value means an empty collection returned as nulls from an outerjoin.
                        return getIndirectionPolicy().valueFromRow(value);
                    } else {
                        containsNull = true;
                    }
                }
                // Only build/add the target object once, skip duplicates from multiple 1-m joins.
                if (!directValues.contains(directValue)) {
                    directValues.add(directValue);
                    // Allow for value conversion.
                    if (valueConverter != null) {
                        directValue = valueConverter.convertDataValueToObjectValue(directValue, executionSession);
                    }
                    if (shouldAddAll) {
                        directValuesList.add(directValue);
                        targetRows.add(targetRow);
                    } else {
                        policy.addInto(directValue, value, executionSession, targetRow, sourceQuery, parentCacheKey, isTargetProtected);
                    }
                }
            }
            if (shouldAddAll) {
                // if collection contains a single element which is null then return an empty collection
                if (!(containsNull && targetRows.size() == 1)) {
                    policy.addAll(directValuesList, value, executionSession, targetRows, sourceQuery, parentCacheKey, isTargetProtected);
                }
            } else {
                // if collection contains a single element which is null then return an empty collection
                if (containsNull && policy.sizeFor(value) == 1) {
                    policy.clear(value);
                }
            }
        }
        return getIndirectionPolicy().valueFromRow(value);
    }

    /**
     * INTERNAL:
     * Copy of the attribute of the object.
     * This is NOT used for unit of work but for templatizing an object.
     */
    @Override
    public void buildCopy(Object copy, Object original, CopyGroup group) {
        Object attributeValue = getRealCollectionAttributeValueFromObject(original, group.getSession());
        attributeValue = getContainerPolicy().cloneFor(attributeValue);
        // if value holder is used, then the value holder shared with original substituted for a new ValueHolder.
        getIndirectionPolicy().reset(copy);
        setRealAttributeValueInObject(copy, attributeValue);
    }

    /**
     * INTERNAL:
     * Clone the element, if necessary.
     * DirectCollections hold on to objects that do not have Descriptors
     * (e.g. int, String). These objects do not need to be cloned, unless they use a converter - they
     * are immutable.
     */
    @Override
    public Object buildElementClone(Object element, Object parent, CacheKey parentCacheKey, Integer refreshCascade, AbstractSession cloningSession, boolean isExisting, boolean isFromSharedCache) {
        Object cloneValue = element;
        if ((getValueConverter() != null) && getValueConverter().isMutable()) {
            cloneValue = getValueConverter().convertDataValueToObjectValue(getValueConverter().convertObjectValueToDataValue(cloneValue, cloningSession), cloningSession);
        }
        return cloneValue;
    }

    /**
     * INTERNAL:
     * In case Query By Example is used, this method builds and returns an expression that
     * corresponds to a single attribute and it's value.
     */
    @Override
    public Expression buildExpression(Object queryObject, QueryByExamplePolicy policy, Expression expressionBuilder, Map processedObjects, AbstractSession session) {
        if (policy.shouldValidateExample()){
            throw QueryException.unsupportedMappingQueryByExample(queryObject.getClass().getName(), this);
        }
        return null;
    }

    /**
     * INTERNAL:
     * Verifies listOrderField's table: it must be reference table.
     * Precondition: listOrderField != null.
     */
    @Override
    protected void buildListOrderField() {
        if(this.listOrderField.hasTableName()) {
            if(!getReferenceTable().equals(this.listOrderField.getTable())) {
                throw DescriptorException.listOrderFieldTableIsWrong(this.getDescriptor(), this, this.listOrderField.getTable(), getReferenceTable());
            }
        } else {
            this.listOrderField.setTable(getReferenceTable());
        }
        this.listOrderField = getDescriptor().buildField(this.listOrderField, getReferenceTable());
    }

    /**
     * INTERNAL:
     * Cascade perform delete through mappings that require the cascade
     */
    @Override
    public void cascadePerformRemoveIfRequired(Object object, UnitOfWorkImpl uow, Map visitedObjects) {
        //as this mapping type references primitive objects this method does not apply
    }

    /**
     * INTERNAL:
     * Cascade perform removal of orphaned private owned objects from the UnitOfWorkChangeSet
     */
    @Override
    public void cascadePerformRemovePrivateOwnedObjectFromChangeSetIfRequired(Object object, UnitOfWorkImpl uow, Map visitedObjects) {
        // as this mapping type references primitive objects this method does not apply
    }

    /**
     * INTERNAL:
     * Cascade registerNew for Create through mappings that require the cascade
     */
    @Override
    public void cascadeRegisterNewIfRequired(Object object, UnitOfWorkImpl uow, Map visitedObjects) {
        //as this mapping type references primitive objects this method does not apply
    }

    /**
     * INTERNAL:
     * Cascade discover and persist new objects during commit.
     */
    @Override
    public void cascadeDiscoverAndPersistUnregisteredNewObjects(Object object, Map newObjects, Map unregisteredExistingObjects, Map visitedObjects, UnitOfWorkImpl uow, Set cascadeErrors) {
        // Direct mappings do not require any cascading.
    }

    /**
     * INTERNAL:
     * The mapping clones itself to create deep copy.
     */
    @Override
    public Object clone() {
        DirectCollectionMapping clone = (DirectCollectionMapping)super.clone();

        clone.setSourceKeyFields(cloneFields(getSourceKeyFields()));
        clone.setReferenceKeyFields(cloneFields(getReferenceKeyFields()));

        if(this.changeSetDeleteQuery != null) {
            clone.changeSetDeleteQuery = (ModifyQuery)this.changeSetDeleteQuery.clone();
        }

        // Bug 306075
        if(this.changeSetDeleteNullQuery != null) {
            clone.changeSetDeleteNullQuery = (ModifyQuery)this.changeSetDeleteNullQuery.clone();
        }

        if(this.deleteAtIndexQuery != null) {
            clone.deleteAtIndexQuery = (ModifyQuery)this.deleteAtIndexQuery.clone();
        }
        if(this.updateAtIndexQuery != null) {
            clone.updateAtIndexQuery = (ModifyQuery)this.updateAtIndexQuery.clone();
        }

        return clone;
    }

    /**
     * INTERNAL:
     * This method is used to calculate the differences between two collections.
     */
    @Override
    public void compareCollectionsForChange(Object oldCollection, Object newCollection, ChangeRecord changeRecord, AbstractSession session) {
        if(this.listOrderField != null) {
            compareListsForChange((List)oldCollection, (List)newCollection, changeRecord, session);
            return;
        }
        ContainerPolicy cp = getContainerPolicy();
        int numberOfNewNulls = 0;

        HashMap originalKeyValues = new HashMap(10);
        HashMap cloneKeyValues = new HashMap(10);

        if (oldCollection != null) {
            Object backUpIter = cp.iteratorFor(oldCollection);

            while (cp.hasNext(backUpIter)) {// Make a lookup of the objects
                Object secondObject = cp.next(backUpIter, session);

                // For CR#2258/CR#2378 handle null values inserted in a collection.
                if (secondObject == null) {
                    numberOfNewNulls--;
                } else {
                    Integer count = (Integer)originalKeyValues.get(secondObject);
                    if (count == null) {
                        originalKeyValues.put(secondObject, 1);
                    } else {
                        originalKeyValues.put(secondObject, count + 1);
                    }
                }
            }
        }

        // should a removal occur this is the original count of objects on the database.
        // this value is used to determine how many objects to re-insert after the delete as a
        // delete will delete all of the objects not just one.
        HashMap databaseCount = (HashMap)originalKeyValues.clone();
        int databaseNullCount = Math.abs(numberOfNewNulls);

        if (newCollection != null) {
            Object cloneIter = cp.iteratorFor(newCollection);

            /* The following code is used to compare objects in a direct collection.
               Because objects in a direct collection are primitives and may be the same object
               the following code must count the number of instances in the collection not just the
               existence of an object.
            */
            while (cp.hasNext(cloneIter)) {//Compare them with the objects from the clone
                Object firstObject = cp.next(cloneIter, session);

                // For CR#2258/CR#2378 handle null values inserted in a collection.
                if (firstObject == null) {
                    numberOfNewNulls++;
                } else {
                    Integer count = (Integer)originalKeyValues.get(firstObject);
                    if (count == null) {//the object was not in the backup
                        Integer cloneCount = (Integer)cloneKeyValues.get(firstObject);

                        //Add it to the additions hashtable
                        if (cloneCount == null) {
                            cloneKeyValues.put(firstObject, 1);
                        } else {
                            cloneKeyValues.put(firstObject, cloneCount + 1);
                        }
                    } else if (count == 1) {
                        //There is only one object so remove the whole reference
                        originalKeyValues.remove(firstObject);
                    } else {
                        originalKeyValues.put(firstObject, count - 1);
                    }
                }
            }
        }
        if (cloneKeyValues.isEmpty() && originalKeyValues.isEmpty() && (numberOfNewNulls == 0) && (!changeRecord.getOwner().isNew())) {
            return;
        }
        ((DirectCollectionChangeRecord)changeRecord).clearChanges();
        ((DirectCollectionChangeRecord)changeRecord).addAdditionChange(cloneKeyValues, databaseCount);
        ((DirectCollectionChangeRecord)changeRecord).addRemoveChange(originalKeyValues, databaseCount);
        ((DirectCollectionChangeRecord)changeRecord).setIsDeferred(false);
        ((DirectCollectionChangeRecord)changeRecord).setLatestCollection(null);
        //For CR#2258, produce a changeRecord which reflects the addition and removal of null values.
        if (numberOfNewNulls != 0) {
            ((DirectCollectionChangeRecord)changeRecord).getCommitAddMap().put(null, databaseNullCount);
            if (numberOfNewNulls > 0) {
                ((DirectCollectionChangeRecord)changeRecord).addAdditionChange(null, numberOfNewNulls);
            } else {
                numberOfNewNulls *= -1;
                ((DirectCollectionChangeRecord)changeRecord).addRemoveChange(null, numberOfNewNulls);
            }
        }
    }

    /**
     * INTERNAL:
     * This method is used to calculate the differences between two Lists.
     */
    public void compareListsForChange(List oldList, List newList, ChangeRecord changeRecord, AbstractSession session) {
        // Maps objects (null included) in newList and oldList to an array of two Sets:
        // the first one contains indexes of the object in oldList, the second - in newList.
        // Contains only the objects for which the set of indexes in newList and oldList are different;
        // only changed indexes appear in the sets (therefore the old index set and new index set don't intersect).
        // Examples:
        //    obj was first (index 0) in oldList; first and second (indexes 0 and 1)in newList: obj -> {{}, {1}};
        //    obj was not in oldList; first in newList: obj -> {null, {0}};
        //    obj was first in oldList; not in newList: obj -> {{0}, null};
        //    obj was first and second in oldList; first in newList: obj -> {{1}, {}};
        // Note the difference between null and empty set:
        //    empty set means there's at least one index (the same in oldList and newList - otherwise it would've been in the set);
        //    null means there's no indexes.
        // That helps during deletion - if we know there is no remaining duplicates for the object to be removed
        // we can delete it without checking its index (which allows delete several duplicates in one sql).
        // Map entry sets with no new and no old indexes removed.

        int nOldSize = oldList == null ? 0 : oldList.size();
        int nNewSize = newList == null ? 0 : newList.size();
        HashMap<Object, Set[]> changedIndexes = new HashMap<>(Math.max(nOldSize, nNewSize));

        // for each object in oldList insert all its indexes in oldList into the old indexes set corresponding to each object.
        if (oldList != null) {
            for(int i=0; i < nOldSize; i++) {
                Object obj = oldList.get(i);
                Set[] indexes = changedIndexes.get(obj);
                if (indexes == null) {
                    // the first index found for the object.
                    indexes = new Set[]{new HashSet(), null};
                    changedIndexes.put(obj, indexes);
                }
                indexes[0].add(i);
            }
        }

        // helper set to store objects for which entries into changedIndexes has been removed:
        // if an entry for the object is created again, it will have an empty old indexes set (rather than null)
        // to indicate that the object has been on the oldList, too.
        HashSet removedFromChangedIndexes = new HashSet();
        HashSet dummySet = new HashSet(0);

        // for each object in newList, for each its index in newList:
        //   if the object has the same index in oldList - remove the index from old indexes set;
        //   if the object doesn't have the same index in oldList - insert the index into new indexes set.
        if (newList != null) {
            for(int i=0; i < nNewSize; i++) {
                Object obj = newList.get(i);
                Set[] indexes = changedIndexes.get(obj);
                if (indexes == null) {
                    // the first index found for the object - or was found and removed before.
                    if(removedFromChangedIndexes.contains(obj)) {
                        // the object also exists in oldList
                        indexes = new Set[]{dummySet, new HashSet()};
                    } else {
                        // the object does not exist in oldList
                        indexes = new Set[]{null, new HashSet()};
                    }
                    changedIndexes.put(obj, indexes);
                    // the object doesn't have this index in oldList - add the index to new indexes set.
                    indexes[1].add(i);
                } else {
                    if(indexes[0] == null || !indexes[0].contains(i)) {
                        // the object doesn't have this index in oldList - add the index to new indexes set.
                        if(indexes[1] == null) {
                            indexes[1] = new HashSet();
                        }
                        indexes[1].add(i);
                    } else {
                        // the object has this index in oldList - remove the index from the old indexes set.
                        indexes[0].remove(i);
                        if(indexes[0].isEmpty()) {
                            // no old indexes left for the object.
                            if(indexes[1] == null || indexes[1].isEmpty()) {
                                // no new indexes left, too - remove the entry for the object.
                                changedIndexes.remove(obj);
                                // store the object in case it has another index on newList
                                removedFromChangedIndexes.add(obj);
                            }
                        }
                    }
                }
            }
        }

        ((DirectCollectionChangeRecord)changeRecord).setChangedIndexes(changedIndexes);
        ((DirectCollectionChangeRecord)changeRecord).setOldSize(nOldSize);
        ((DirectCollectionChangeRecord)changeRecord).setNewSize(nNewSize);
    }

    /**
     * INTERNAL:
     * This method compares the changes between two direct collections.  Comparisons are made on equality
     * not identity.
     */
    @Override
    public ChangeRecord compareForChange(Object clone, Object backUp, ObjectChangeSet owner, AbstractSession session) {
        Object cloneAttribute = getAttributeValueFromObject(clone);
        Object backUpAttribute = null;

        if ((cloneAttribute != null) && (!getIndirectionPolicy().objectIsInstantiated(cloneAttribute))) {
            return null;
        }

        Object cloneObjectCollection = getRealCollectionAttributeValueFromObject(clone, session);
        Object backUpCollection = null;

        if (!owner.isNew()) {
            backUpAttribute = getAttributeValueFromObject(backUp);

            if ((backUpAttribute == null) && (cloneAttribute == null)) {
                return null;
            }

            backUpCollection = getRealCollectionAttributeValueFromObject(backUp, session);
        }
        DirectCollectionChangeRecord changeRecord = new DirectCollectionChangeRecord(owner);
        changeRecord.setAttribute(getAttributeName());
        changeRecord.setMapping(this);
        if(this.listOrderField != null) {
            changeRecord.setLatestCollection(cloneObjectCollection);
        }
        compareCollectionsForChange(backUpCollection, cloneObjectCollection, changeRecord, session);
        if (changeRecord.hasChanges()) {
            changeRecord.setOriginalCollection(backUpCollection);
            return changeRecord;
        }
        return null;
    }

    /**
     * INTERNAL:
     * Compare the attributes belonging to this mapping for the objects.
     */
    @Override
    public boolean compareObjects(Object firstObject, Object secondObject, AbstractSession session) {
        Object firstCollection = getRealCollectionAttributeValueFromObject(firstObject, session);
        Object secondCollection = getRealCollectionAttributeValueFromObject(secondObject, session);
        if(this.listOrderField != null) {
            return compareLists((List)firstCollection, (List)secondCollection);
        }
        ContainerPolicy containerPolicy = getContainerPolicy();

        if (containerPolicy.sizeFor(firstCollection) != containerPolicy.sizeFor(secondCollection)) {
            return false;
        }

        HashMap firstCounter = new HashMap();
        HashMap secondCounter = new HashMap();
        for (Object iter = containerPolicy.iteratorFor(firstCollection);
                 containerPolicy.hasNext(iter);) {
            Object object = containerPolicy.next(iter, session);
            if (firstCounter.containsKey(object)) {
                int count = (Integer) firstCounter.get(object);
                firstCounter.put(object, ++count);
            } else {
                firstCounter.put(object, 1);
            }
        }
        for (Object iter = containerPolicy.iteratorFor(secondCollection);
                 containerPolicy.hasNext(iter);) {
            Object object = containerPolicy.next(iter, session);
            if (secondCounter.containsKey(object)) {
                int count = (Integer) secondCounter.get(object);
                secondCounter.put(object, ++count);
            } else {
                secondCounter.put(object, 1);
            }
        }
        for (Iterator iterator = firstCounter.keySet().iterator(); iterator.hasNext();) {
            Object object = iterator.next();

            if (!secondCounter.containsKey(object) || (((Integer)secondCounter.get(object)).intValue() != ((Integer)firstCounter.get(object)).intValue())) {
                // containsKey(object) will fail when the objects are arrays.
                boolean found = false;

                for (Iterator ii = secondCounter.keySet().iterator(); ii.hasNext();) {
                    Object otherObject = ii.next();
                    if(object == otherObject) {
                        found = true;
                    } else if(object == null || otherObject == null) {
                        found = false;
                    } else {
                        found = Helper.comparePotentialArrays(object, otherObject);
                    }

                    if (found) {
                        iterator.remove();
                        secondCounter.remove(otherObject);
                        break;
                    }
                }

                if (!found) {
                    return false;
                }
            } else {
                iterator.remove();
                secondCounter.remove(object);
            }
        }
        if (!firstCounter.isEmpty() || !secondCounter.isEmpty()) {
            return false;
        }
        return true;
    }

    /**
     * Compare two lists. For equality the order of the elements should be the same.
     * Used only if listOrderField != null
     */
    protected boolean compareLists(List firstList, List secondList) {
        if (firstList.size() != secondList.size()) {
            return false;
        }

        int size = firstList.size();
        for(int i=0; i < size; i++) {
            Object firstObject = firstList.get(i);
            Object secondObject = secondList.get(i);
            if(firstObject != secondObject) {
                if(firstObject==null || secondObject==null) {
                    return false;
                } else {
                    if(!firstObject.equals(secondObject)) {
                        return false;
                    }
                }
            }
        }
        return true;
    }

    /**
     * INTERNAL:
     * Convert all the class-name-based settings in this mapping to actual class-based
     * settings
     * This method is implemented by subclasses as necessary.
     */
    @Override
    public void convertClassNamesToClasses(ClassLoader classLoader) {
        super.convertClassNamesToClasses(classLoader);

        // Tell the direct field to convert any class names (type name).
        directField.convertClassNamesToClasses(classLoader);

        // Convert and any Converter class names.
        convertConverterClassNamesToClasses(valueConverter, classLoader);

        // Instantiate any custom converter class
        if (valueConverterClassName != null) {
            Class valueConverterClass;
            Converter valueConverter;

            try {
                if (PrivilegedAccessHelper.shouldUsePrivilegedAccess()){
                    try {
                        valueConverterClass = AccessController.doPrivileged(new PrivilegedClassForName<>(valueConverterClassName, true, classLoader));
                    } catch (PrivilegedActionException exception) {
                        throw ValidationException.classNotFoundWhileConvertingClassNames(valueConverterClassName, exception.getException());
                    }

                    try {
                        valueConverter = (Converter) AccessController.doPrivileged(new PrivilegedNewInstanceFromClass(valueConverterClass));
                    } catch (PrivilegedActionException exception) {
                        throw ValidationException.classNotFoundWhileConvertingClassNames(valueConverterClassName, exception.getException());
                    }
                } else {
                    valueConverterClass = PrivilegedAccessHelper.getClassForName(valueConverterClassName, true, classLoader);
                    valueConverter = (Converter) PrivilegedAccessHelper.newInstanceFromClass(valueConverterClass);
                }
            } catch (ClassNotFoundException exc) {
                throw ValidationException.classNotFoundWhileConvertingClassNames(valueConverterClassName, exc);
            } catch (Exception e) {
                // Catches IllegalAccessException and InstantiationException
                throw ValidationException.classNotFoundWhileConvertingClassNames(valueConverterClassName, e);
            }

            setValueConverter(valueConverter);
        }

        // Check if the attribute classification is set (either directly or through a type conversion converter)
        if (attributeClassification == null) {
            // Look for an attribute classification name
            if (attributeClassificationName != null) {
                try {
                    if (PrivilegedAccessHelper.shouldUsePrivilegedAccess()){
                        try {
                            attributeClassification = AccessController.doPrivileged(new PrivilegedClassForName<>(attributeClassificationName, true, classLoader));
                        } catch (PrivilegedActionException pae) {
                            throw ValidationException.classNotFoundWhileConvertingClassNames(attributeClassificationName, pae.getException());
                        }
                    } else {
                        attributeClassification = PrivilegedAccessHelper.getClassForName(attributeClassificationName, true, classLoader);
                    }
                } catch (Exception exception) {
                    throw ValidationException.classNotFoundWhileConvertingClassNames(attributeClassificationName, exception);
                }
            } else {
                // Still nothing, default to the type from the direct field.
                attributeClassification = getDirectField().getType();
            }
        }
    }

    /**
     * INTERNAL:
     * Extract the source primary key value from the reference direct row.
     * Used for batch reading, most following same order and fields as in the mapping.
     */
    @Override
    protected Object extractKeyFromTargetRow(AbstractRecord row, AbstractSession session) {
        int size = this.referenceKeyFields.size();
        Object[] key = new Object[size];
        ConversionManager conversionManager = session.getDatasourcePlatform().getConversionManager();
        for (int index = 0; index < size; index++) {
            DatabaseField relationField = this.referenceKeyFields.get(index);
            DatabaseField sourceField = this.sourceKeyFields.get(index);
            Object value = row.get(relationField);
            // Must ensure the classification gets a cache hit.
            try {
                value = conversionManager.convertObject(value, sourceField.getType());
            } catch (ConversionException e) {
                throw ConversionException.couldNotBeConverted(this, getDescriptor(), e);
            }
            key[index] = value;
        }
        return new CacheId(key);
    }

    /**
     * INTERNAL:
     * Extract the primary key value from the source row.
     * Used for batch reading, most following same order and fields as in the mapping.
     */
    @Override
    protected Object extractBatchKeyFromRow(AbstractRecord row, AbstractSession session) {
        int size = this.sourceKeyFields.size();
        Object[] key = new Object[size];
        ConversionManager conversionManager = session.getDatasourcePlatform().getConversionManager();
        for (int index = 0; index < size; index++) {
            DatabaseField field = this.sourceKeyFields.get(index);
            Object value = row.get(field);
            // Must ensure the classification to get a cache hit.
            try {
                value = conversionManager.convertObject(value, field.getType());
            } catch (ConversionException exception) {
                throw ConversionException.couldNotBeConverted(this, this.descriptor, exception);
            }
            key[index] = value;
        }
        return new CacheId(key);
    }

    /**
     * INTERNAL:
     * Return the selection criteria used to IN batch fetching.
     */
    @Override
    protected Expression buildBatchCriteria(ExpressionBuilder builder, ObjectLevelReadQuery query) {
        int size = this.referenceKeyFields.size();
        Expression table = builder.getTable(this.referenceTable);
        if (size > 1) {
            // Support composite keys using nested IN.
            List<Expression> fields = new ArrayList<>(size);
            for (DatabaseField referenceKeyField : this.referenceKeyFields) {
                fields.add(table.getField(referenceKeyField));
            }
            return query.getSession().getPlatform().buildBatchCriteriaForComplexId(builder, fields);
        } else {
            return query.getSession().getPlatform().buildBatchCriteria(builder, table.getField(this.referenceKeyFields.get(0)));
        }
    }

    /**
     * INTERNAL:
     * Prepare and execute the batch query and store the
     * results for each source object in a map keyed by the
     * mappings source keys of the source objects.
     */
    @Override
    protected void executeBatchQuery(DatabaseQuery query, CacheKey parentCacheKey, Map referenceDataByKey, AbstractSession session, AbstractRecord translationRow) {
        // Execute query and index resulting object sets by key.
        List<AbstractRecord> rows = (List<AbstractRecord>)session.executeQuery(query, translationRow);
        int size = rows.size();
        if (this.containerPolicy.shouldAddAll()) {
            if (size > 0) {
                Map<Object, List[]> referenceDataAndRowsByKey = new HashMap();
                for (int index = 0; index < size; index++) {
                    AbstractRecord referenceRow = rows.get(index);
                    Object referenceValue = referenceRow.get(this.directField);
                    Object eachReferenceKey = extractKeyFromTargetRow(referenceRow, session);

                    // Allow for value conversion.
                    if (this.valueConverter != null) {
                        referenceValue = this.valueConverter.convertDataValueToObjectValue(referenceValue, query.getSession());
                    }
                    List[] valuesAndRows = referenceDataAndRowsByKey.get(eachReferenceKey);
                    if (valuesAndRows == null) {
                        valuesAndRows = new List[]{new ArrayList(), new ArrayList()};
                        referenceDataAndRowsByKey.put(eachReferenceKey, valuesAndRows);
                    }
                    valuesAndRows[0].add(referenceValue);
                    valuesAndRows[1].add(referenceRow);
                }

                Iterator<Map.Entry<Object, List[]>> iterator = referenceDataAndRowsByKey.entrySet().iterator();
                while (iterator.hasNext()) {
                    Map.Entry<Object, List[]> entry = iterator.next();
                    Object eachReferenceKey = entry.getKey();
                    List referenceValues = entry.getValue()[0];
                    List<AbstractRecord> referenceRows = entry.getValue()[1];
                    Object container = this.containerPolicy.containerInstance(referenceValues.size());
                    this.containerPolicy.addAll(referenceValues, container, query.getSession(), referenceRows, (DataReadQuery)query, parentCacheKey, true);
                    referenceDataByKey.put(eachReferenceKey, container);
                }
            }
        } else {
            for (int index = 0; index < size; index++) {
                AbstractRecord referenceRow = rows.get(index);
                Object referenceValue = referenceRow.get(this.directField);
                Object eachReferenceKey = extractKeyFromTargetRow(referenceRow, session);

                Object container = referenceDataByKey.get(eachReferenceKey);
                if ((container == null) || (container == Helper.NULL_VALUE)) {
                    container = this.containerPolicy.containerInstance();
                    referenceDataByKey.put(eachReferenceKey, container);
                }

                // Allow for value conversion.
                if (this.valueConverter != null) {
                    referenceValue = this.valueConverter.convertDataValueToObjectValue(referenceValue, query.getSession());
                }
                this.containerPolicy.addInto(referenceValue, container, query.getSession());
            }
        }
    }

    /**
     * INTERNAL:
     * At this point, we realize we don't have indirection;
     * so we need to replace the reference object(s) with
     * the corresponding object(s) from the remote session.
     *
     * The reference objects for a DirectCollectionMapping
     * are primitives, so they do not need to be replaced.
     */
    @Override
    public void fixRealObjectReferences(Object object, Map<Object, ObjectDescriptor> objectInformation, Map<Object, Object> processedObjects, ObjectLevelReadQuery query, DistributedSession session) {
        // do nothing
    }


    /**
     * PUBLIC:
     * Some databases do not properly support all of the base data types. For these databases,
     * the base data type must be explicitly specified in the mapping to tell EclipseLink to force
     * the instance variable value to that data type.
     * @since Java Persistence API 2.0
     */
    @Override
    public Class getAttributeClassification() {
        return attributeClassification;
    }

    /**
     * INTERNAL:
     * Return the class name of the attribute type.
     * This is only used by the MW.
     * @since Java Persistence API 2.0
     */
    public String getAttributeClassificationName() {
        if ((null == attributeClassificationName) && (attributeClassification != null)) {
            attributeClassificationName = attributeClassification.getName();
        }
        return attributeClassificationName;
    }

    protected ModifyQuery getDeleteQuery() {
        if (changeSetDeleteQuery == null) {
            changeSetDeleteQuery = new DataModifyQuery();
        }
        return changeSetDeleteQuery;
    }

    // Bug 306075
    protected ModifyQuery getDeleteNullQuery() {
        if (changeSetDeleteNullQuery == null) {
            changeSetDeleteNullQuery = new DataModifyQuery();
        }
        return changeSetDeleteNullQuery;
    }

    protected ModifyQuery getDeleteAtIndexQuery() {
        if (deleteAtIndexQuery == null) {
            deleteAtIndexQuery = new DataModifyQuery();
        }
        return deleteAtIndexQuery;
    }

    protected ModifyQuery getUpdateAtIndexQuery() {
        if (updateAtIndexQuery == null) {
            updateAtIndexQuery = new DataModifyQuery();
        }
        return updateAtIndexQuery;
    }

    /**
     * INTERNAL:
     * Returns the set of fields that should be selected to build this mapping's value(s).
     * This is used by expressions to determine which fields to include in the select clause for non-object expressions.
     */
    @Override
    public Vector getSelectFields() {
        Vector<DatabaseField> fields = new NonSynchronizedVector<>(2);
        fields.add(getDirectField());
        return fields;
    }

    /**
     * INTERNAL:
     * Returns the table(s) that should be selected to build this mapping's value(s).
     * This is used by expressions to determine which tables to include in the from clause for non-object expressions.
     */
    @Override
    public Vector getSelectTables() {
        Vector<DatabaseTable> tables = new NonSynchronizedVector<>(0);
        tables.add(getReferenceTable());
        return tables;
    }

    /**
     * INTERNAL:
     * Return the direct field.
     * This is the field in the direct table to store the values.
     */
    public DatabaseField getDirectField() {
        return directField;
    }

    /**
     * PUBLIC:
     * Returns the name of the field name in the reference table.
     */
    public String getDirectFieldName() {
        if (getDirectField() == null) {
            return null;
        }
        return getDirectField().getQualifiedName();
    }

    protected DataModifyQuery getInsertQuery() {
        return insertQuery;
    }

    /**
     * INTERNAL:
     * Returns the join criteria stored in the mapping selection query. This criteria
     * is used to read reference objects across the tables from the database.
     */
    @Override
    public Expression getJoinCriteria(ObjectExpression context, Expression base) {
        if (getHistoryPolicy() != null) {
            Expression result = super.getJoinCriteria(context, base);
            Expression historyCriteria = getHistoryPolicy().additionalHistoryExpression(context, base);
            if (result != null) {
                return result.and(historyCriteria);
            } else if (historyCriteria != null) {
                return historyCriteria;
            } else {
                return null;
            }
        } else {
            return super.getJoinCriteria(context, base);
        }
    }

    /**
     * INTERNAL:
     * return the object on the client corresponding to the specified object.
     * DirectCollections do not have to worry about
     * maintaining object identity.
     */
    @Override
    public Object getObjectCorrespondingTo(Object object, DistributedSession session, Map<Object, ObjectDescriptor> objectDescriptors, Map<Object, Object> processedObjects, ObjectLevelReadQuery query) {
        return object;
    }

    /**
     * PUBLIC:
     * Return the order by expression.
     */
    public List<Expression> getOrderByExpressions() {
        return orderByExpressions;
    }

    /**
     * INTERNAL:
     * Return null if this mapping is used in an order by.
     */
    @Override
    public List<Expression> getOrderByNormalizedExpressions(Expression base) {
        return null;
    }

    /**
     * PUBLIC:
     * Allow history support on the reference table.
     */
    public HistoryPolicy getHistoryPolicy() {
        return historyPolicy;
    }

    /**
     * INTERNAL:
     * Get the container policy from the selection query for this mapping.
     */
    @Override
    protected ContainerPolicy getSelectionQueryContainerPolicy() {
        return ((DataReadQuery) getSelectionQuery()).getContainerPolicy();
    }

    /**
     * INTERNAL:
     * This cannot be used with direct collection mappings.
     */
    @Override
    public Class getReferenceClass() {
        return null;
    }

    @Override
    public String getReferenceClassName() {
        return null;
    }

    /**
     * INTERNAL:
     * There is none on direct collection.
     */
    @Override
    public ClassDescriptor getReferenceDescriptor() {
        return null;
    }

    /**
     * INTERNAL:
     * Return the reference key field names associated with the mapping.
     * These are in-order with the sourceKeyFieldNames.
     */
    public Vector getReferenceKeyFieldNames() {
        Vector fieldNames = new Vector(getReferenceKeyFields().size());
        for (Enumeration<DatabaseField> fieldsEnum = getReferenceKeyFields().elements();
             fieldsEnum.hasMoreElements();) {
            fieldNames.addElement(fieldsEnum.nextElement().getQualifiedName());
        }

        return fieldNames;
    }

    /**
     * INTERNAL:
     * Return the reference key fields.
     */
    public Vector<DatabaseField> getReferenceKeyFields() {
        return referenceKeyFields;
    }

    /**
     * INTERNAL:
     * Return the direct table.
     * This is the table to store the values.
     */
    public DatabaseTable getReferenceTable() {
        return referenceTable;
    }

    /**
     * PUBLIC:
     * Returns the name of the reference table
     */
    public String getReferenceTableName() {
        if (getReferenceTable() == null) {
            return null;
        }
        return getReferenceTable().getName();
    }

    //This method is added to include table qualifier.

    /**
     * PUBLIC:
     * Returns the qualified name of the reference table.
     */
    public String getReferenceTableQualifiedName() {//CR#2407
        if (getReferenceTable() == null) {
            return null;
        }
        return getReferenceTable().getQualifiedName();
    }

    /**
     * INTERNAL:
     * Return the relationshipPartner mapping for this bi-directional mapping. If the relationshipPartner is null then
     * this is a uni-directional mapping.
     * DirectCollectionMapping can not be part of a bi-directional mapping
     */
    @Override
    public DatabaseMapping getRelationshipPartner() {
        return null;
    }

    /**
     * PUBLIC:
     * Return the source key field names associated with the mapping.
     * These are in-order with the referenceKeyFieldNames.
     */
    public Vector getSourceKeyFieldNames() {
        Vector fieldNames = new Vector(getSourceKeyFields().size());
        for (Enumeration<DatabaseField> fieldsEnum = getSourceKeyFields().elements();
             fieldsEnum.hasMoreElements();) {
            fieldNames.addElement(fieldsEnum.nextElement().getQualifiedName());
        }

        return fieldNames;
    }

    /**
     * INTERNAL:
     * Return the source key fields.
     */
    public Vector<DatabaseField> getSourceKeyFields() {
        return sourceKeyFields;
    }

    protected boolean hasCustomDeleteQuery() {
        return hasCustomDeleteQuery;
    }

    protected boolean hasCustomInsertQuery() {
        return hasCustomInsertQuery;
    }

    protected boolean hasCustomDeleteAtIndexQuery() {
        return hasCustomDeleteAtIndexQuery;
    }

    protected boolean hasCustomUpdateAtIndexQuery() {
        return hasCustomUpdateAtIndexQuery;
    }

    /**
     * INTERNAL:
     * Indicates whether the mapping (or at least one of its nested mappings, at any nested depth)
     * references an entity.
     * To return true the mapping (or nested mapping) should be ForeignReferenceMapping with non-null and non-aggregate reference descriptor.
     */
    @Override
    public boolean hasNestedIdentityReference() {
        return false;
    }

    /**
     * INTERNAL:
     * Initialize and validate the mapping properties.
     */
    @Override
    public void initialize(AbstractSession session) throws DescriptorException {
        if (session.hasBroker()) {
            if (getInsertQuery().hasSessionName()) {
                // substitute session that owns the mapping for the session that owns reference table.
                session = session.getBroker().getSessionForName(getInsertQuery().getSessionName());
            }
        }

        if (isKeyForSourceSpecified()) {
            initializeSourceKeys(session);
        } else {
            initializeSourceKeysWithDefaults(session);
        }

        initializeReferenceTable(session);
        initializeReferenceKeys(session);
        initializeDirectField(session);

        if (getReferenceTable().getName().indexOf(' ') != -1) {
            //table names contains a space so needs to be quoted.
            String beginQuote = session.getDatasourcePlatform().getStartDelimiter();
            String endQuote = session.getDatasourcePlatform().getEndDelimiter();
            //Ensure this tablename hasn't already been quoted.
            if (getReferenceTable().getName().indexOf(beginQuote) == -1) {
                getReferenceTable().setName(beginQuote + getReferenceTable().getName() + endQuote);
            }
        }
        if (this.listOrderField != null) {
            this.initializeListOrderField(session);
        }
        getContainerPolicy().initialize(session, this.referenceTable);

        // Initialize the value converter sooner since it likely will finish
        // configuring field and attribute classifications.
        if (getValueConverter() != null) {
            getValueConverter().initialize(this, session);
        }

        if (!hasCustomSelectionQuery()){
            initOrRebuildSelectQuery();
            getSelectionQuery().setName(getAttributeName());

            if (shouldInitializeSelectionCriteria()) {
                initializeSelectionCriteria(session);
                initializeSelectionStatement(session);
            }
        }
        if (!getSelectionQuery().hasSessionName()) {
            getSelectionQuery().setSessionName(session.getName());
        }
        if (getSelectionQuery().getPartitioningPolicy() == null) {
            getSelectionQuery().setPartitioningPolicy(getPartitioningPolicy());
        }
        getSelectionQuery().setSourceMapping(this);
        if ((getValueConverter() != null) && (getSelectionQuery() instanceof DirectReadQuery)) {
            ((DirectReadQuery)getSelectionQuery()).setValueConverter(getValueConverter());
        }
        initializeDeleteAllQuery(session);
        initializeDeleteQuery(session);
        initializeDeleteNullQuery(session); // Bug 306075
        initializeInsertQuery(session);
        initializeDeleteAtIndexQuery(session);
        initializeUpdateAtIndexQuery(session);
        if (getHistoryPolicy() != null) {
            getHistoryPolicy().initialize(session);
        }
        super.initialize(session);
    }

    /**
     * INTERNAL:
     * Initializes listOrderField.
     * Precondition: listOrderField != null.
     */
    @Override
    protected void initializeListOrderField(AbstractSession session) {
        // This method is called twice. The second call (by CollectionMapping.initialize) should be ignored because initialization has been already done.
        if(!getContainerPolicy().isOrderedListPolicy() || ((OrderedListContainerPolicy)getContainerPolicy()).getListOrderField() == null) {
            super.initializeListOrderField(session);
        }
    }

    /**
     * Initialize delete all query. This query is used to delete the collection of objects from the
     * reference table.
     */
    protected void initializeDeleteAllQuery(AbstractSession session) {
        if (!getDeleteAllQuery().hasSessionName()) {
            getDeleteAllQuery().setSessionName(session.getName());
        }
        if (getDeleteAllQuery().getPartitioningPolicy() == null) {
            getDeleteAllQuery().setPartitioningPolicy(getPartitioningPolicy());
        }

        if (hasCustomDeleteAllQuery()) {
            return;
        }

        Expression expression = null;
        Expression subExp1;
        Expression subExp2;
        Expression subExpression;
        Expression builder = new ExpressionBuilder();
        SQLDeleteStatement statement = new SQLDeleteStatement();

        // Construct an expression to delete from the relation table.
        for (int index = 0; index < getReferenceKeyFields().size(); index++) {
            DatabaseField referenceKey = getReferenceKeyFields().elementAt(index);
            DatabaseField sourceKey = getSourceKeyFields().elementAt(index);

            subExp1 = builder.getField(referenceKey);
            subExp2 = builder.getParameter(sourceKey);
            subExpression = subExp1.equal(subExp2);

            if (expression == null) {
                expression = subExpression;
            } else {
                expression = expression.and(subExpression);
            }
        }

        statement.setWhereClause(expression);
        statement.setTable(getReferenceTable());
        getDeleteAllQuery().setSQLStatement(statement);
    }

    protected void initializeDeleteQuery(AbstractSession session) {
        if (!getDeleteQuery().hasSessionName()) {
            getDeleteQuery().setSessionName(session.getName());
        }
        if (getDeleteQuery().getPartitioningPolicy() == null) {
            getDeleteQuery().setPartitioningPolicy(getPartitioningPolicy());
        }

        if (hasCustomDeleteQuery()) {
            return;
        }

        SQLDeleteStatement statement = new SQLDeleteStatement();
        ExpressionBuilder builder = new ExpressionBuilder();
        Expression expression = createWhereClauseForDeleteQuery(builder);
        statement.setWhereClause(expression);
        statement.setTable(getReferenceTable());
        getDeleteQuery().setSQLStatement(statement);
    }

    // Bug 306075 - for deleting a null value from a collection
    protected void initializeDeleteNullQuery(AbstractSession session) {
        if (!getDeleteNullQuery().hasSessionName()) {
            getDeleteNullQuery().setSessionName(session.getName());
        }
        if (getDeleteNullQuery().getPartitioningPolicy() == null) {
            getDeleteNullQuery().setPartitioningPolicy(getPartitioningPolicy());
        }

        SQLDeleteStatement statement = new SQLDeleteStatement();
        ExpressionBuilder builder = new ExpressionBuilder();
        Expression expression = createWhereClauseForDeleteNullQuery(builder);
        statement.setWhereClause(expression);
        statement.setTable(getReferenceTable());
        getDeleteNullQuery().setSQLStatement(statement);
    }

    protected void initializeDeleteAtIndexQuery(AbstractSession session) {
        if (!getDeleteAtIndexQuery().hasSessionName()) {
            getDeleteAtIndexQuery().setSessionName(session.getName());
        }
        if (getDeleteAtIndexQuery().getPartitioningPolicy() == null) {
            getDeleteAtIndexQuery().setPartitioningPolicy(getPartitioningPolicy());
        }

        if (hasCustomDeleteAtIndexQuery()) {
            return;
        }

        SQLDeleteStatement statement = new SQLDeleteStatement();
        ExpressionBuilder builder = new ExpressionBuilder();
        Expression expression = createWhereClauseForDeleteQuery(builder);
        expression = expression.and(builder.getField(this.listOrderField).equal(builder.getParameter(this.listOrderField)));
        statement.setWhereClause(expression);
        statement.setTable(getReferenceTable());
        getDeleteAtIndexQuery().setSQLStatement(statement);
    }

    protected void initializeUpdateAtIndexQuery(AbstractSession session) {
        if (!getUpdateAtIndexQuery().hasSessionName()) {
            getUpdateAtIndexQuery().setSessionName(session.getName());
        }
        if (getUpdateAtIndexQuery().getPartitioningPolicy() == null) {
            getUpdateAtIndexQuery().setPartitioningPolicy(getPartitioningPolicy());
        }
        if (hasCustomUpdateAtIndexQuery()) {
            return;
        }

        SQLUpdateStatement statement = new SQLUpdateStatement();
        ExpressionBuilder builder = new ExpressionBuilder();
        Expression expression = createWhereClauseForDeleteQuery(builder);
        expression = expression.and(builder.getField(this.listOrderField).equal(builder.getParameter(this.listOrderField)));
        statement.setWhereClause(expression);
        statement.setTable(getReferenceTable());
        AbstractRecord modifyRow = new DatabaseRecord();
        modifyRow.add(this.listOrderField, null);
        statement.setModifyRow(modifyRow);
        getUpdateAtIndexQuery().setSQLStatement(statement);
    }

    /**
     * INTERNAL:
     * Indicates whether getListOrderFieldExpression method should create field expression on table expression.
     */
    @Override
    public boolean shouldUseListOrderFieldTableExpression() {
        return true;
    }

    protected Expression createWhereClauseForDeleteQuery(ExpressionBuilder builder) {
        Expression directExp = builder.getField(getDirectField()).equal(builder.getParameter(getDirectField()));
        Expression expression = null;

        // Construct an expression to delete from the relation table.
        for (int index = 0; index < getReferenceKeyFields().size(); index++) {
            DatabaseField referenceKey = getReferenceKeyFields().get(index);
            DatabaseField sourceKey = getSourceKeyFields().get(index);

            Expression subExp1 = builder.getField(referenceKey);
            Expression subExp2 = builder.getParameter(sourceKey);
            Expression subExpression = subExp1.equal(subExp2);

            expression = subExpression.and(expression);
        }
        expression = expression.and(directExp);
        return expression;
    }

    // Bug 306075 - for deleting a null value from a collection
    protected Expression createWhereClauseForDeleteNullQuery(ExpressionBuilder builder) {
        Expression directExp = builder.getField(getDirectField()).isNull();
        Expression expression = null;

        // Construct an expression to delete from the relation table.
        for (int index = 0; index < getReferenceKeyFields().size(); index++) {
            DatabaseField referenceKey = getReferenceKeyFields().get(index);
            DatabaseField sourceKey = getSourceKeyFields().get(index);

            Expression subExp1 = builder.getField(referenceKey);
            Expression subExp2 = builder.getParameter(sourceKey);
            Expression subExpression = subExp1.equal(subExp2);

            expression = subExpression.and(expression);
        }
        expression = expression.and(directExp);
        return expression;
    }

    /**
     * The field name on the reference table is initialized and cached.
     */
    protected void initializeDirectField(AbstractSession session) throws DescriptorException {
        if (getDirectField() == null) {
            throw DescriptorException.directFieldNameNotSet(this);
        }

        getDirectField().setTable(getReferenceTable());
        getDirectField().setIndex(0);
    }

    /**
     * Initialize insert query. This query is used to insert the collection of objects into the
     * reference table.
     */
    protected void initializeInsertQuery(AbstractSession session) {
        if (!getInsertQuery().hasSessionName()) {
            getInsertQuery().setSessionName(session.getName());
        }
        if (getInsertQuery().getPartitioningPolicy() == null) {
            getInsertQuery().setPartitioningPolicy(getPartitioningPolicy());
        }

        if (hasCustomInsertQuery()) {
            return;
        }

        SQLInsertStatement statement = new SQLInsertStatement();
        statement.setTable(getReferenceTable());
        AbstractRecord directRow = new DatabaseRecord();
        for (Enumeration<DatabaseField> referenceEnum = getReferenceKeyFields().elements();
             referenceEnum.hasMoreElements();) {
            directRow.put(referenceEnum.nextElement(), null);
        }
        directRow.put(getDirectField(), null);
        if(listOrderField != null) {
            directRow.put(listOrderField, null);
        }
        statement.setModifyRow(directRow);
        getInsertQuery().setSQLStatement(statement);
        getInsertQuery().setModifyRow(directRow);
    }

    /**
     * There is no reference descriptor
     */
    @Override
    protected void initializeReferenceDescriptor(AbstractSession session) {
        // no-op.
    }

    /**
     * The reference keys on the reference table are initialized
     */
    protected void initializeReferenceKeys(AbstractSession session) throws DescriptorException {
        if (getReferenceKeyFields().size() == 0) {
            throw DescriptorException.noReferenceKeyIsSpecified(this);
        }

        for (Enumeration<DatabaseField> referenceEnum = getReferenceKeyFields().elements(); referenceEnum.hasMoreElements();) {
            DatabaseField field = referenceEnum.nextElement();

            // Update the field first if the mapping is on a table per tenant entity.
            if (getDescriptor().hasTablePerMultitenantPolicy()) {
                field.setTable(((TablePerMultitenantPolicy) getDescriptor().getMultitenantPolicy()).getTable(field.getTable()));
            }

            if (field.hasTableName() && (!(field.getTableName().equals(getReferenceTable().getName())))) {
                throw DescriptorException.referenceKeyFieldNotProperlySpecified(field, this);
            }
            field.setTable(getReferenceTable());
        }
    }

    /**
     * Set the table qualifier on the reference table if required
     */
    protected void initializeReferenceTable(AbstractSession session) throws DescriptorException {
        Platform platform = session.getDatasourcePlatform();

        if (getReferenceTable() == null) {
            throw DescriptorException.referenceTableNotSpecified(this);
        }

        if (platform.getTableQualifier().length() > 0) {
            if (getReferenceTable().getTableQualifier().length() == 0) {
                getReferenceTable().setTableQualifier(platform.getTableQualifier());
            }
        }
    }

    protected void initializeSelectionCriteria(AbstractSession session) {
        Expression criteria = null;
        ExpressionBuilder base = new ExpressionBuilder();
        TableExpression table = (TableExpression)base.getTable(getReferenceTable());
        Iterator<DatabaseField> referenceKeys = getReferenceKeyFields().iterator();
        Iterator<DatabaseField> sourceKeys = getSourceKeyFields().iterator();
        while (referenceKeys.hasNext()) {
            DatabaseField referenceKey = referenceKeys.next();
            DatabaseField sourceKey = sourceKeys.next();
            Expression expression = table.getField(referenceKey).equal(base.getParameter(sourceKey));
            if (criteria == null) {
                criteria = expression;
            } else {
                criteria = expression.and(criteria);
            }
        }
        setSelectionCriteria(criteria);
    }

    /**
     * The selection query is initialized
     */
    @Override
    protected void initializeSelectionQuery(AbstractSession session) {
        // Nothing required.
    }

    protected void initializeSelectionStatement(AbstractSession session) {
        SQLSelectStatement statement = new SQLSelectStatement();
        statement.addTable(getReferenceTable());
        statement.addField(getDirectField().clone());
        statement.setWhereClause(getSelectionCriteria());
        statement.setOrderByExpressions(orderByExpressions);
        getSelectionQuery().setSQLStatement(statement);
        getContainerPolicy().addAdditionalFieldsToQuery(selectionQuery, getAdditionalFieldsBaseExpression(getSelectionQuery()));
        statement.normalize(session, null);
    }

    /**
     * The source keys are initialized
     */
    protected void initializeSourceKeys(AbstractSession session) {
        for (int index = 0; index < getSourceKeyFields().size(); index++) {
            DatabaseField field = getDescriptor().buildField(getSourceKeyFields().get(index));
            if (usesIndirection()) {
                field.setKeepInRow(true);
            }
            getSourceKeyFields().set(index, field);
        }
    }

    /**
     * INTERNAL:
     * If a user does not specify the source key then the primary keys of the source table are used.
     */
    protected void initializeSourceKeysWithDefaults(AbstractSession session) {
        List<DatabaseField> primaryKeyFields = getDescriptor().getPrimaryKeyFields();
        for (int index = 0; index < primaryKeyFields.size(); index++) {
            DatabaseField field = primaryKeyFields.get(index);
            if (usesIndirection()) {
                field.setKeepInRow(true);
            }
            getSourceKeyFields().addElement(field);
        }
    }

    /**
     * INTERNAL:
     * Return the base expression to use for adding fields to the query.
     * This is the reference table.
     */
    @Override
    protected Expression getAdditionalFieldsBaseExpression(ReadQuery query) {
        if (query.isReadAllQuery()) {
            return ((ReadAllQuery)query).getExpressionBuilder();
        } else {
            return query.getSQLStatement().getBuilder().getTable(getReferenceTable());
        }
    }

    /**
     * INTERNAL:
     */
    @Override
    public boolean isDirectCollectionMapping() {
        return true;
    }

    /**
     * INTERNAL:
     */
    @Override
    public boolean isElementCollectionMapping() {
        return true;
    }

    /**
     * INTERNAL:
     * Return if this mapping support joining.
     */
    @Override
    public boolean isJoiningSupported() {
        return true;
    }

    /**
     * INTERNAL:
     * Checks if source and target keys are mentioned by the user or not.
     */
    protected boolean isKeyForSourceSpecified() {
        return !getSourceKeyFields().isEmpty();
    }

    /**
     * INTERNAL:
     * Return whether this mapping should be traversed when we are locking
     */
    @Override
    public boolean isLockableMapping(){
        return false;
    }

    /**
     * INTERNAL:
     */
    @Override
    public boolean isOwned(){
        return true;
    }

    /**
     * INTERNAL:
     * Iterate on the attribute value.
     * The value holder has already been processed.
     * PERF: Avoid iteration if not required.
     */
    @Override
    public void iterateOnRealAttributeValue(DescriptorIterator iterator, Object realAttributeValue) {
        if (iterator.shouldIterateOnPrimitives()) {
            super.iterateOnRealAttributeValue(iterator, realAttributeValue);
        }
    }

    /**
     * INTERNAL:
     * Iterate on the specified element.
     */
    @Override
    public void iterateOnElement(DescriptorIterator iterator, Object element) {
        iterator.iteratePrimitiveForMapping(element, this);
    }

    /**
     * INTERNAL:
     * Merge changes from the source to the target object.
     * Because this is a collection mapping, values are added to or removed from the
     * collection based on the changeset
     */
    @Override
    public void mergeChangesIntoObject(Object target, ChangeRecord changeRecord, Object source, MergeManager mergeManager, AbstractSession targetSession) {
        if (this.descriptor.getCachePolicy().isProtectedIsolation()&& !this.isCacheable && !targetSession.isProtectedSession()){
            setAttributeValueInObject(target, this.indirectionPolicy.buildIndirectObject(new ValueHolder<>(null)));
            return;
        }
        ContainerPolicy containerPolicy = getContainerPolicy();
        Object valueOfTarget = null;
        AbstractSession session = mergeManager.getSession();

        DirectCollectionChangeRecord directCollectionChangeRecord = (DirectCollectionChangeRecord) changeRecord;

        //Check to see if the target has an instantiated collection
        if ((isAttributeValueInstantiated(target)) && (!changeRecord.getOwner().isNew())) {
            if (isSynchronizeOnMerge) {
                valueOfTarget = getRealCollectionAttributeValueFromObject(target, session);
            } else {
                valueOfTarget = containerPolicy.cloneFor(getRealCollectionAttributeValueFromObject(target, session));
            }
        } else {
            //if not create an instance of the collection
            valueOfTarget = containerPolicy.containerInstance(directCollectionChangeRecord.getAddObjectMap().size());
        }
        if (!isAttributeValueInstantiated(target)) {
            if (mergeManager.shouldMergeChangesIntoDistributedCache()) {
                return;
            }
            for (Object iterator = containerPolicy.iteratorFor(getRealCollectionAttributeValueFromObject(source, session));
                     containerPolicy.hasNext(iterator);) {
                containerPolicy.addInto(containerPolicy.next(iterator, session), valueOfTarget, session);
            }
        } else {
            Object synchronizationTarget = valueOfTarget;
            // For indirect containers the delegate must be synchronized on,
            // not the wrapper as the clone synchs on the delegate, see bug#5685287.
            if (valueOfTarget instanceof IndirectCollection) {
                synchronizationTarget = ((IndirectCollection)valueOfTarget).getDelegateObject();
                if (((DirectCollectionChangeRecord)changeRecord).orderHasBeenRepaired() && (valueOfTarget instanceof IndirectList)) {
                    ((IndirectList)valueOfTarget).setIsListOrderBrokenInDb(false);
                }
            }
            if (isSynchronizeOnMerge) {
                synchronized(synchronizationTarget) {
                    mergeAddRemoveChanges(valueOfTarget, synchronizationTarget, directCollectionChangeRecord, mergeManager, session);
                }
            } else {
                mergeAddRemoveChanges(valueOfTarget, synchronizationTarget, directCollectionChangeRecord, mergeManager, session);
            }
        }
        setRealAttributeValueInObject(target, valueOfTarget);
    }

    /**
     * INTERNAL:
     * Merge changes by adding and removing from the change record to the
     * target object, and its delegate object if instance of IndirectCollection.
     * It will also reorder the collection if required.
     */
    protected void mergeAddRemoveChanges(Object valueOfTarget, Object delegateTarget, DirectCollectionChangeRecord changeRecord, MergeManager mergeManager, AbstractSession session) {
        //collect the changes into a vector
        HashMap addObjects = changeRecord.getAddObjectMap();
        HashMap removeObjects = changeRecord.getRemoveObjectMap();

        // Next iterate over the changes and add them to the container
        for (Iterator iterator = addObjects.keySet().iterator(); iterator.hasNext();) {
            Object object = iterator.next();
            int objectCount = (Integer) addObjects.get(object);
            for (int i = 0; i < objectCount; ++i) {
                if (mergeManager.shouldMergeChangesIntoDistributedCache()) {
                    //bug#4458089 and 4544532- check if collection contains new item before adding during merge into distributed cache
                    if (!containerPolicy.contains(object, valueOfTarget, session)) {
                        containerPolicy.addInto(object, valueOfTarget, session);
                    }
                } else {
                    containerPolicy.addInto(object, valueOfTarget, session);
                }
            }
        }
        for (Iterator iterator = removeObjects.keySet().iterator(); iterator.hasNext();) {
            Object object = iterator.next();
            int objectCount = (Integer) removeObjects.get(object);
            for (int i = 0; i < objectCount; ++i) {
                containerPolicy.removeFrom(object, valueOfTarget, session);
            }
        }
        if(this.listOrderField != null && changeRecord.getChangedIndexes() == null) {
            this.compareListsForChange((List)changeRecord.getOriginalCollection(), (List)changeRecord.getLatestCollection(), changeRecord, session);
        }

        if(changeRecord.getChangedIndexes() != null) {
            int oldSize = changeRecord.getOldSize();
            int newSize = changeRecord.getNewSize();
            int delta = newSize - oldSize;
            Object[] newTail = null;
            if(delta > 0) {
                newTail = new Object[delta];
            }
            Iterator<Map.Entry<Object, Set[]>> it = changeRecord.getChangedIndexes().entrySet().iterator();
            while(it.hasNext()) {
                Map.Entry<Object, Set[]> entry = it.next();
                Object value = entry.getKey();
                Set[] indexes = entry.getValue();
                Set indexesAfter = indexes[1];
                if(indexesAfter != null) {
                    Iterator<Integer> itIndexesAfter = indexesAfter.iterator();
                    while(itIndexesAfter.hasNext()) {
                        int index = itIndexesAfter.next();
                        if(index < oldSize) {
                            ((List)delegateTarget).set(index, value);
                        } else {
                            newTail[index - oldSize] = value;
                        }
                    }
                }
            }
            if(delta > 0) {
                for(int i=0; i < delta; i++) {
                    ((List)delegateTarget).add(newTail[i]);
                }
            } else if(delta < 0) {
                for(int i=oldSize -1 ; i >= newSize; i--) {
                    ((List)delegateTarget).remove(i);
                }
            }
        }
    }

    /**
     * INTERNAL:
     * Merge changes from the source to the target object.
     */
    @Override
    public void mergeIntoObject(Object target, boolean isTargetUnInitialized, Object source, MergeManager mergeManager, AbstractSession targetSession) {
        if (this.descriptor.getCachePolicy().isProtectedIsolation() && !this.isCacheable && !targetSession.isProtectedSession()){
            setAttributeValueInObject(target, this.indirectionPolicy.buildIndirectObject(new ValueHolder<>(null)));
            return;
        }
        if (isTargetUnInitialized) {
            // This will happen if the target object was removed from the cache before the commit was attempted
            if (mergeManager.shouldMergeWorkingCopyIntoOriginal() && (!isAttributeValueInstantiated(source))) {
                setAttributeValueInObject(target, getIndirectionPolicy().getOriginalIndirectionObject(getAttributeValueFromObject(source), targetSession));
                return;
            }
        }
        if (!shouldMergeCascadeReference(mergeManager)) {
            // This is only going to happen on mergeClone, and we should not attempt to merge the reference
            return;
        }
        if (mergeManager.shouldRefreshRemoteObject() && usesIndirection()) {
            mergeRemoteValueHolder(target, source, mergeManager);
            return;
        }
        if (mergeManager.isForRefresh()) {
            if (!isAttributeValueInstantiated(target)) {
                // This will occur when the clone's value has not been instantiated yet and we do not need
                // the refresh that attribute
                return;
            }
        } else if (!isAttributeValueInstantiatedOrChanged(source)) {
            // I am merging from a clone into an original.  No need to do merge if the attribute was never
            // modified
            return;
        }

        ContainerPolicy containerPolicy = getContainerPolicy();
        Object valueOfSource = getRealCollectionAttributeValueFromObject(source, mergeManager.getSession());

        // trigger instantiation of target attribute
        Object valueOfTarget = getRealCollectionAttributeValueFromObject(target, mergeManager.getSession());
        Object newContainer = containerPolicy.containerInstance(containerPolicy.sizeFor(valueOfSource));
        boolean fireCollectionChangeEvents = false;
        boolean firePropertyChangeEvent = false;
        ObjectChangeListener listener = null;
        if ((this.descriptor.getObjectChangePolicy().isObjectChangeTrackingPolicy()) && (target instanceof ChangeTracker) && (((ChangeTracker)target)._persistence_getPropertyChangeListener() != null)) {
            listener = (ObjectChangeListener)((ChangeTracker)target)._persistence_getPropertyChangeListener();
            if(this.listOrderField == null) {
                fireCollectionChangeEvents = true;
                //Collections may not be indirect list or may have been replaced with user collection.
                Object iterator = containerPolicy.iteratorFor(valueOfTarget);
                Integer zero = 0;//remove does not seem to use index.
                while (containerPolicy.hasNext(iterator)) {
                    // Bug304251: let the containerPolicy build the proper remove CollectionChangeEvent
                    CollectionChangeEvent event = containerPolicy.createChangeEvent(target, getAttributeName(), valueOfTarget, containerPolicy.next(iterator, mergeManager.getSession()), CollectionChangeEvent.REMOVE, zero, false);
                    listener.internalPropertyChange(event);
                }
                if (newContainer instanceof ChangeTracker) {
                    ((ChangeTracker)newContainer)._persistence_setPropertyChangeListener(((ChangeTracker)target)._persistence_getPropertyChangeListener());
                }
                if (valueOfTarget instanceof ChangeTracker) {
                    ((ChangeTracker)valueOfTarget)._persistence_setPropertyChangeListener(null);//remove listener
                }
            } else {
                firePropertyChangeEvent = true;
            }
        }
        Object originalValueOfTarget = valueOfTarget;
        valueOfTarget = newContainer;
        int i = 0;
        for (Object sourceValuesIterator = containerPolicy.iteratorFor(valueOfSource);
                 containerPolicy.hasNext(sourceValuesIterator);) {
            Object sourceValue = containerPolicy.next(sourceValuesIterator, mergeManager.getSession());
            if (fireCollectionChangeEvents) {
                // Bug304251: let the containerPolicy build the proper remove CollectionChangeEvent
                CollectionChangeEvent event = containerPolicy.createChangeEvent(target, getAttributeName(), valueOfTarget, sourceValue, CollectionChangeEvent.ADD, i, false);
                listener.internalPropertyChange(event);
            }
            containerPolicy.addInto(sourceValue, valueOfTarget, mergeManager.getSession());
            i++;
        }
        if (fireCollectionChangeEvents && (this.descriptor.getObjectChangePolicy().isAttributeChangeTrackingPolicy())) {
            // check that there were changes, if not then remove the record.
            ObjectChangeSet changeSet = ((AttributeChangeListener)((ChangeTracker)target)._persistence_getPropertyChangeListener()).getObjectChangeSet();
            if (changeSet != null) {
                DirectCollectionChangeRecord changeRecord = (DirectCollectionChangeRecord)changeSet.getChangesForAttributeNamed(getAttributeName());
                if (changeRecord != null) {
                    if (!changeRecord.isDeferred()) {
                        if (!changeRecord.hasChanges()) {
                            changeSet.removeChange(getAttributeName());
                        }
                    } else {
                        // Must reset the latest collection.
                        changeRecord.setLatestCollection(valueOfTarget);
                    }
                }
            }
        }

        if(firePropertyChangeEvent) {
            ((ObjectChangeListener)((ChangeTracker)target)._persistence_getPropertyChangeListener()).internalPropertyChange(new PropertyChangeEvent(target, getAttributeName(), originalValueOfTarget, valueOfTarget));
            if (valueOfTarget instanceof ChangeTracker) {
                ((ChangeTracker)valueOfTarget)._persistence_setPropertyChangeListener(((ChangeTracker)target)._persistence_getPropertyChangeListener());
            }
            if (originalValueOfTarget instanceof ChangeTracker) {
                ((ChangeTracker)originalValueOfTarget)._persistence_setPropertyChangeListener(null);//remove listener
            }
        }

        // Must re-set variable to allow for set method to re-morph changes if the collection is not being stored directly.
        setRealAttributeValueInObject(target, valueOfTarget);
    }

    /**
     * INTERNAL:
     * Perform the commit event.
     * This is used in the uow to delay data modifications.
     */
    @Override
    public void performDataModificationEvent(Object[] event, AbstractSession session) throws DatabaseException, DescriptorException {
        // Hey I might actually want to use an inner class here... ok array for now.
        if (event[0] == Delete) {
            session.executeQuery((DataModifyQuery)event[1], (AbstractRecord)event[2]);
            if ((getHistoryPolicy() != null) && getHistoryPolicy().shouldHandleWrites()) {
                getHistoryPolicy().mappingLogicalDelete((DataModifyQuery)event[1], (AbstractRecord)event[2], session);
            }
        } else if (event[0] == Insert) {
            session.executeQuery((DataModifyQuery)event[1], (AbstractRecord)event[2]);
            if ((getHistoryPolicy() != null) && getHistoryPolicy().shouldHandleWrites()) {
                getHistoryPolicy().mappingLogicalInsert((DataModifyQuery)event[1], (AbstractRecord)event[2], session);
            }
        } else if (event[0] == DeleteAll) {
            preDelete((DeleteObjectQuery)event[1]);
        } else if (event[0] == DeleteAtIndex) {
            session.executeQuery((DataModifyQuery)event[1], (AbstractRecord)event[2]);
        } else if (event[0] == UpdateAtIndex) {
            DataModifyQuery updateAtIndexQuery = (DataModifyQuery)((DataModifyQuery)event[1]).clone();
            updateAtIndexQuery.setModifyRow((AbstractRecord)event[3]);
            updateAtIndexQuery.setHasModifyRow(true);
            updateAtIndexQuery.setIsExecutionClone(true);
            session.executeQuery(updateAtIndexQuery, (AbstractRecord)event[2]);
        } else {
            throw DescriptorException.invalidDataModificationEventCode(event[0], this);
        }
    }

    /**
     * INTERNAL:
     * Overridden by mappings that require additional processing of the change record after the record has been calculated.
     */
    @Override
    public void postCalculateChanges(org.eclipse.persistence.sessions.changesets.ChangeRecord changeRecord, UnitOfWorkImpl uow) {
        //no -op for this collection type
    }

    /**
     * INTERNAL:
     * Insert the private owned object.
     */
    @Override
    public void postInsert(WriteObjectQuery query) throws DatabaseException {
        Object objects;
        AbstractRecord databaseRow = new DatabaseRecord();

        if (isReadOnly()) {
            return;
        }

        objects = getRealCollectionAttributeValueFromObject(query.getObject(), query.getSession());
        ContainerPolicy containerPolicy = getContainerPolicy();
        if (containerPolicy.isEmpty(objects)) {
            return;
        }

        prepareTranslationRow(query.getTranslationRow(), query.getObject(), query.getDescriptor(), query.getSession());
        // Extract primary key and value from the source.
        for (int index = 0; index < getReferenceKeyFields().size(); index++) {
            DatabaseField referenceKey = getReferenceKeyFields().get(index);
            DatabaseField sourceKey = getSourceKeyFields().get(index);
            Object sourceKeyValue = query.getTranslationRow().get(sourceKey);
            databaseRow.put(referenceKey, sourceKeyValue);
        }

        int orderIndex = 0;
        // Extract target field and its value. Construct insert statement and execute it
        for (Object iter = containerPolicy.iteratorFor(objects); containerPolicy.hasNext(iter);) {
            Object wrappedObject = containerPolicy.nextEntry(iter, query.getSession());
            Object object = containerPolicy.unwrapIteratorResult(wrappedObject);
            if (getValueConverter() != null) {
                object = getValueConverter().convertObjectValueToDataValue(object, query.getSession());
            }
            databaseRow.put(getDirectField(), object);

            // In the uow data queries are cached until the end of the commit.
            if (query.shouldCascadeOnlyDependentParts()) {
                // Hey I might actually want to use an inner class here... ok array for now.
                Object[] event = new Object[3];
                event[0] = Insert;
                event[1] = getInsertQuery();
                event[2] = databaseRow.clone();
                if(listOrderField != null) {
                    ((AbstractRecord)event[2]).put(listOrderField, orderIndex++);
                }
                query.getSession().getCommitManager().addDataModificationEvent(this, event);
            } else {
                query.getSession().executeQuery(getInsertQuery(), databaseRow);
                if ((getHistoryPolicy() != null) && getHistoryPolicy().shouldHandleWrites()) {
                    getHistoryPolicy().mappingLogicalInsert(getInsertQuery(), databaseRow, query.getSession());
                }
            }
            containerPolicy.propogatePostInsert(query, wrappedObject);
        }
    }

    /**
     * INTERNAL:
     * Convert the attribute value to a field value.
     * Process any converter if defined.
     */
    public Object getFieldValue(Object attributeValue, AbstractSession session) {
        if (this.valueConverter != null) {
            return this.valueConverter.convertObjectValueToDataValue(attributeValue, session);
        }
        return attributeValue;
    }

    /**
     * INTERNAL:
     * Convert the field value to an attribute value.
     * Process any converter if defined.
     */
    public Object getObjectValue(Object fieldValue, AbstractSession session) {
        if (this.valueConverter != null) {
            return this.valueConverter.convertDataValueToObjectValue(fieldValue, session);
        }
        return fieldValue;
    }

    /**
     * INTERNAL:
     * Return source key fields for translation by an AggregateObjectMapping
     */
    @Override
    public Vector getFieldsForTranslationInAggregate() {
        return getSourceKeyFields();
    }

    /**
     * INTERNAL:
     * Update private owned part.
     */
    @Override
    public void postUpdate(WriteObjectQuery writeQuery) throws DatabaseException {
        if (isReadOnly()) {
            return;
        }

        if (writeQuery.getObjectChangeSet() != null) {
            if(this.listOrderField != null) {
                postUpdateWithChangeSetListOrder(writeQuery);
            } else {
                postUpdateWithChangeSet(writeQuery);
            }
            return;
        }

        // If objects are not instantiated that means they are not changed.
        if (!isAttributeValueInstantiatedOrChanged(writeQuery.getObject())) {
            return;
        }

        if (writeQuery.getSession().isUnitOfWork()) {
            if (compareObjects(writeQuery.getObject(), writeQuery.getBackupClone(), writeQuery.getSession())) {
                return;// Nothing has changed, no work required
            }
        }

        DeleteObjectQuery deleteQuery = new DeleteObjectQuery();
        deleteQuery.setObject(writeQuery.getObject());
        deleteQuery.setSession(writeQuery.getSession());
        deleteQuery.setTranslationRow(writeQuery.getTranslationRow());

        if (writeQuery.shouldCascadeOnlyDependentParts()) {
            // Hey I might actually want to use an inner class here... ok array for now.
            Object[] event = new Object[3];
            event[0] = DeleteAll;
            event[1] = deleteQuery;
            writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
        } else {
            preDelete(deleteQuery);
        }
        postInsert(writeQuery);
    }

    /**
     * INTERNAL:
     * Update private owned part.
     */
    protected void postUpdateWithChangeSet(WriteObjectQuery writeQuery) throws DatabaseException {
        ObjectChangeSet changeSet = writeQuery.getObjectChangeSet();
        DirectCollectionChangeRecord changeRecord = (DirectCollectionChangeRecord)changeSet.getChangesForAttributeNamed(this.getAttributeName());
        if (changeRecord == null) {
            return;
        }
        for (int index = 0; index < getReferenceKeyFields().size(); index++) {
            DatabaseField referenceKey = getReferenceKeyFields().get(index);
            DatabaseField sourceKey = getSourceKeyFields().get(index);
            Object sourceKeyValue = writeQuery.getTranslationRow().get(sourceKey);
            writeQuery.getTranslationRow().put(referenceKey, sourceKeyValue);
        }
        for (Iterator iterator = changeRecord.getRemoveObjectMap().keySet().iterator();
                 iterator.hasNext();) {
            Object object = iterator.next();
            AbstractRecord thisRow = writeQuery.getTranslationRow().clone();
            Object value = getFieldValue(object, writeQuery.getSession());

            // Hey I might actually want to use an inner class here... ok array for now.
            Object[] event = new Object[3];
            event[0] = Delete;
            if (value == null) { // Bug 306075 - for deleting a null value from a collection
                event[1] = getDeleteNullQuery();
             } else {
                thisRow.add(getDirectField(), value);
                event[1] = getDeleteQuery();
             }
            event[2] = thisRow;
            writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
            Integer count = (Integer)changeRecord.getCommitAddMap().get(object);
            if (count != null) {
                for (int counter = count; counter > 0; --counter) {
                    thisRow = writeQuery.getTranslationRow().clone();
                    thisRow.add(getDirectField(), value);
                    // Hey I might actually want to use an inner class here... ok array for now.
                    event = new Object[3];
                    event[0] = Insert;
                    event[1] = getInsertQuery();
                    event[2] = thisRow;
                    writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
                }
            }
        }
        for (Iterator iterator = changeRecord.getAddObjectMap().keySet().iterator();
                 iterator.hasNext();) {
            Object object = iterator.next();
            Integer count = (Integer)changeRecord.getAddObjectMap().get(object);
            for (int counter = count; counter > 0; --counter) {
                AbstractRecord thisRow = writeQuery.getTranslationRow().clone();
                Object value = object;
                if (getValueConverter() != null) {
                    value = getValueConverter().convertObjectValueToDataValue(value, writeQuery.getSession());
                }
                thisRow.add(getDirectField(), value);

                // Hey I might actually want to use an inner class here... ok array for now.
                Object[] event = new Object[3];
                event[0] = Insert;
                event[1] = getInsertQuery();
                event[2] = thisRow;
                writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
            }
        }
    }

    /**
     * INTERNAL:
     * Update private owned part.
     */
    protected void postUpdateWithChangeSetListOrder(WriteObjectQuery writeQuery) throws DatabaseException {
        ObjectChangeSet changeSet = writeQuery.getObjectChangeSet();
        DirectCollectionChangeRecord changeRecord = (DirectCollectionChangeRecord)changeSet.getChangesForAttributeNamed(this.getAttributeName());
        if (changeRecord == null) {
            return;
        }
        for (int index = 0; index < getReferenceKeyFields().size(); index++) {
            DatabaseField referenceKey = getReferenceKeyFields().get(index);
            DatabaseField sourceKey = getSourceKeyFields().get(index);
            Object sourceKeyValue = writeQuery.getTranslationRow().get(sourceKey);
            writeQuery.getTranslationRow().put(referenceKey, sourceKeyValue);
        }

        boolean shouldRepairOrder = false;
        if(changeRecord.getLatestCollection() instanceof IndirectList) {
            shouldRepairOrder = ((IndirectList)changeRecord.getLatestCollection()).isListOrderBrokenInDb();
        }
        if(shouldRepairOrder) {
            // delete all members of collection
            DeleteObjectQuery deleteQuery = new DeleteObjectQuery();
            deleteQuery.setObject(writeQuery.getObject());
            deleteQuery.setSession(writeQuery.getSession());
            deleteQuery.setTranslationRow(writeQuery.getTranslationRow());
            // Hey I might actually want to use an inner class here... ok array for now.
            Object[] eventDeleteAll = new Object[2];
            eventDeleteAll[0] = DeleteAll;
            eventDeleteAll[1] = deleteQuery;
            writeQuery.getSession().getCommitManager().addDataModificationEvent(this, eventDeleteAll);

            // re-insert them back
            for(int i=0; i < ((List)changeRecord.getLatestCollection()).size(); i++) {
                Object value = ((List)changeRecord.getLatestCollection()).get(i);
                value = getFieldValue(value, writeQuery.getSession());
                AbstractRecord insertRow = writeQuery.getTranslationRow().clone();
                insertRow.add(getDirectField(), value);
                insertRow.add(this.listOrderField, i);
                // Hey I might actually want to use an inner class here... ok array for now.
                Object[] event = new Object[3];
                event[0] = Insert;
                event[1] = getInsertQuery();
                event[2] = insertRow;
                writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
            }

            ((IndirectList)changeRecord.getLatestCollection()).setIsListOrderBrokenInDb(false);
            changeRecord.setOrderHasBeenRepaired(true);
            return;
        }

        if(changeRecord.getChangedIndexes() == null) {
            compareListsForChange((List)changeRecord.getOriginalCollection(), (List)changeRecord.getLatestCollection(), changeRecord, writeQuery.getSession());
        }

        Iterator<Map.Entry<Object, Set[]>> it = changeRecord.getChangedIndexes().entrySet().iterator();
        while(it.hasNext()) {
            Map.Entry<Object, Set[]> entry = it.next();
            Object value = entry.getKey();
            if (getValueConverter() != null) {
                value = getValueConverter().convertObjectValueToDataValue(value, writeQuery.getSession());
            }

            Set[] indexes = entry.getValue();
            Set indexesBefore = indexes[0];
            Set indexesAfter = indexes[1];

            if(indexesAfter == null) {
                // All copies of the target object deleted - don't need to verify order field contents.
                AbstractRecord deleteRow = writeQuery.getTranslationRow().clone();

                // Hey I might actually want to use an inner class here... ok array for now.
                Object[] event = new Object[3];
                event[0] = Delete;
                if (value == null) { // Bug 306075 - for deleting a null value from a collection
                    event[1] = getDeleteNullQuery();
                 } else {
                    deleteRow.add(getDirectField(), value);
                    event[1] = getDeleteQuery();
                 }
                event[2] = deleteRow;
                writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
            } else if(indexesAfter.isEmpty()) {
                // Some copies of the target objects should be deleted, some left in the db
                Iterator<Integer> itBefore = indexesBefore.iterator();
                while(itBefore.hasNext()) {
                    AbstractRecord deleteAtIndexRow = writeQuery.getTranslationRow().clone();
                    deleteAtIndexRow.add(getDirectField(), value);
                    deleteAtIndexRow.add(this.listOrderField, itBefore.next());
                    // Hey I might actually want to use an inner class here... ok array for now.
                    Object[] event = new Object[3];
                    event[0] = DeleteAtIndex;
                    event[1] = deleteAtIndexQuery;
                    event[2] = deleteAtIndexRow;
                    writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
                }
            } else {
                if(indexesBefore == null || indexesBefore.isEmpty()) {
                    // insert the object for each index in indexesAfter
                    Iterator<Integer> itAfter = indexesAfter.iterator();
                    while(itAfter.hasNext()) {
                        AbstractRecord insertRow = writeQuery.getTranslationRow().clone();
                        insertRow.add(getDirectField(), value);
                        insertRow.add(this.listOrderField, itAfter.next());
                        // Hey I might actually want to use an inner class here... ok array for now.
                        Object[] event = new Object[3];
                        event[0] = Insert;
                        event[1] = getInsertQuery();
                        event[2] = insertRow;
                        writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
                    }
                } else {
                    Iterator<Integer> itBefore = indexesBefore.iterator();
                    Iterator<Integer> itAfter = indexesAfter.iterator();
                    while(itBefore.hasNext() || itAfter.hasNext()) {
                        if(itBefore.hasNext()) {
                            if(itAfter.hasNext()) {
                                // update the object changing index from indexBefore to indexAfter
                                AbstractRecord updateAtIndexRow = writeQuery.getTranslationRow().clone();
                                updateAtIndexRow.add(getDirectField(), value);
                                updateAtIndexRow.add(this.listOrderField, itBefore.next());
                                // Hey I might actually want to use an inner class here... ok array for now.
                                Object[] event = new Object[4];
                                event[0] = UpdateAtIndex;
                                event[1] = updateAtIndexQuery;
                                event[2] = updateAtIndexRow;
                                DatabaseRecord modifyRow = new DatabaseRecord(1);
                                modifyRow.add(this.listOrderField, itAfter.next());
                                event[3] = modifyRow;
                                writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
                            } else {
                                // delete the object at indexBefore
                                AbstractRecord deleteAtIndexRow = writeQuery.getTranslationRow().clone();
                                deleteAtIndexRow.add(getDirectField(), value);
                                deleteAtIndexRow.add(this.listOrderField, itBefore.next());
                                // Hey I might actually want to use an inner class here... ok array for now.
                                Object[] event = new Object[3];
                                event[0] = DeleteAtIndex;
                                event[1] = deleteAtIndexQuery;
                                event[2] = deleteAtIndexRow;
                                writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
                            }
                        } else {
                            // itAfter.hasNext() must be true
                            // insert the object at indexAfter
                            AbstractRecord insertRow = writeQuery.getTranslationRow().clone();
                            insertRow.add(getDirectField(), value);
                            insertRow.add(this.listOrderField, itAfter.next());
                            // Hey I might actually want to use an inner class here... ok array for now.
                            Object[] event = new Object[3];
                            event[0] = Insert;
                            event[1] = getInsertQuery();
                            event[2] = insertRow;
                            writeQuery.getSession().getCommitManager().addDataModificationEvent(this, event);
                        }
                    }
                }
            }
        }
    }

    /**
     * INTERNAL:
     * Delete private owned part. Which is a collection of objects from the reference table.
     */
    @Override
    public void preDelete(DeleteObjectQuery query) throws DatabaseException {
        if (this.isReadOnly) {
            return;
        }

        if (!this.isCascadeOnDeleteSetOnDatabase) {
            prepareTranslationRow(query.getTranslationRow(), query.getObject(), query.getDescriptor(), query.getSession());
            query.getSession().executeQuery(this.deleteAllQuery, query.getTranslationRow());
        }
        if ((this.historyPolicy != null) && this.historyPolicy.shouldHandleWrites()) {
            if (this.isCascadeOnDeleteSetOnDatabase) {
                prepareTranslationRow(query.getTranslationRow(), query.getObject(), query.getDescriptor(), query.getSession());
            }
            this.historyPolicy.mappingLogicalDelete(this.deleteAllQuery, query.getTranslationRow(), query.getSession());
        }
    }

    /**
     * INTERNAL:
     * The translation row may require additional fields than the primary key if the mapping in not on the primary key.
     */
    @Override
    protected void prepareTranslationRow(AbstractRecord translationRow, Object object, ClassDescriptor descriptor, AbstractSession session) {
        // Make sure that each source key field is in the translation row.
        for (Enumeration<DatabaseField> sourceFieldsEnum = getSourceKeyFields().elements();
             sourceFieldsEnum.hasMoreElements();) {
            DatabaseField sourceKey = sourceFieldsEnum.nextElement();
            if (!translationRow.containsKey(sourceKey)) {
                Object value = descriptor.getObjectBuilder().extractValueFromObjectForField(object, sourceKey, session);
                translationRow.put(sourceKey, value);
            }
        }
    }

    /**
     * INTERNAL:
     * Used by DirectMapMapping to rebuild select query.
     */
    protected void initOrRebuildSelectQuery() {
        this.selectionQuery.setSQLStatement(new SQLSelectStatement());
    }

    /**
     * INTERNAL:
     * Overridden by mappings that require additional processing of the change record after the record has been calculated.
     */
    @Override
    public void recordPrivateOwnedRemovals(Object object, UnitOfWorkImpl uow) {
    }

    /**
     * INTERNAL:
     * Once descriptors are serialized to the remote session. All its mappings and reference descriptors are traversed. Usually
     * mappings are initialized and serialized reference descriptors are replaced with local descriptors if they already exist on the
     * remote session.
     */
    @Override
    public void remoteInitialization(DistributedSession session) {
        // Remote mappings is initialized here again because while serializing only the uninitialized data is passed
        // as the initialized data is not serializable.
        if (!isRemotelyInitialized()) {
            getAttributeAccessor().initializeAttributes(getDescriptor().getJavaClass());
            remotelyInitialized();
        }
    }


    /**
     * INTERNAL:
     * replace the value holders in the specified reference object(s)
     */
    @Override
    public Map replaceValueHoldersIn(Object object, RemoteSessionController controller) {
        // do nothing, since direct collections do not hold onto other domain objects
        return null;
    }

    /**
     * PUBLIC:
     * Some databases do not properly support all of the base data types. For these databases,
     * the base data type must be explicitly specified in the mapping to tell EclipseLink to force
     * the instance variable value to that data type.
     * @since Java Persistence API 2.0
     * Migrated from AbstractDirectMapping
     */
    public void setAttributeClassification(Class attributeClassification) {
        this.attributeClassification = attributeClassification;
    }

    /**
     * INTERNAL:
     * Set the name of the class for MW usage.
     * @since Java Persistence API 2.0
     * Migrated from AbstractDirectMapping
     */
    public void setAttributeClassificationName(String attributeClassificationName) {
        this.attributeClassificationName = attributeClassificationName;
    }

    protected void setDeleteQuery(ModifyQuery query) {
        this.changeSetDeleteQuery = query;
    }

    /**
     * PUBLIC:
     * Set the receiver's delete SQL string. This allows the user to override the SQL
     * generated by TopLink, with there own SQL or procedure call. The arguments are
     * translated from the fields of the source row, through replacing the field names
     * marked by '#' with the values for those fields.
     * This SQL is responsible for doing the deletion required by the mapping,
     * such as deletion from join table for M-M.
     * Example, 'delete from RESPONS where EMP_ID = #EMP_ID and DESCRIP = #DESCRIP'.
     */
    public void setDeleteSQLString(String sqlString) {
        DataModifyQuery query = new DataModifyQuery();
        query.setSQLString(sqlString);
        setCustomDeleteQuery(query);
    }

    /**
     * ADVANCED:
     * Configure the mapping to use a container policy.
     * The policy manages the access to the collection.
     */
    @Override
    public void setContainerPolicy(ContainerPolicy containerPolicy) {
        this.containerPolicy = containerPolicy;
        if (this.selectionQuery.isDataReadQuery()){
            ((DataReadQuery) getSelectionQuery()).setContainerPolicy(containerPolicy);
        }
    }

    /**
     * PUBLIC:
     * The default delete query for this mapping can be overridden by specifying the new query.
     * This query is responsible for doing the deletion required by the mapping,
     * such as deletion from join table for M-M.  The query should delete a specific row from the
     * DirectCollectionTable bases on the DirectField.
     */
    public void setCustomDeleteQuery(ModifyQuery query) {
        setDeleteQuery(query);
        setHasCustomDeleteQuery(true);
    }

    /**
     * PUBLIC:
     * The default delete by index query for this mapping can be overridden by specifying the new query.
     * This query used (only in case listOrderField != null) to delete object with particular orderFieldValue.
     */
    public void setCustomDeleteAtIndexQuery(ModifyQuery query) {
        this.deleteAtIndexQuery = query;
        hasCustomDeleteAtIndexQuery = true;
    }

    /**
     * PUBLIC:
     * The default insert query for mapping can be overridden by specifying the new query.
     * This query inserts the row into the direct table.
     */
    public void setCustomInsertQuery(DataModifyQuery query) {
        setInsertQuery(query);
        setHasCustomInsertQuery(true);
    }

    /**
     * PUBLIC:
     * The default delete by index query for this mapping can be overridden by specifying the new query.
     * This query used (only in case listOrderField != null) to update orderFieldValue of object with particular orderFieldValue.
     */
    public void setCustomUpdateAtIndexQuery(ModifyQuery query) {
        this.updateAtIndexQuery = query;
        hasCustomUpdateAtIndexQuery = true;
    }

    /**
     * PUBLIC:
     * Set the direct field in the reference table.
     * This is the field that the primitive data value is stored in.
     */
    public void setDirectField(DatabaseField field) {
        directField = field;
    }

    /**
     * ADVANCED:
     * Set the class type of the field value.
     * This can be used if field value differs from the object value,
     * has specific typing requirements such as usage of java.sql.Blob or NChar.
     * This must be called after the field name has been set.
     */
    public void setDirectFieldClassification(Class fieldType) {
        getDirectField().setType(fieldType);
    }

    /**
     * ADVANCED:
     * Set the class type of the field value.
     * This can be used if field value differs from the object value,
     * has specific typing requirements such as usage of java.sql.Blob or NChar.
     * This must be called after the field name has been set.
     */
    public void setDirectFieldClassificationName(String className) {
        getDirectField().setTypeName(className);
    }

    /**
     * PUBLIC:
     * Set the direct field name in the reference table.
     * This is the field that the primitive data value is stored in.
     */
    public void setDirectFieldName(String fieldName) {
        setDirectField(new DatabaseField(fieldName));
    }

    protected void setHasCustomDeleteQuery(boolean bool) {
        hasCustomDeleteQuery = bool;
    }

    protected void setHasCustomInsertQuery(boolean bool) {
        hasCustomInsertQuery = bool;
    }

    protected void setInsertQuery(DataModifyQuery insertQuery) {
        this.insertQuery = insertQuery;
    }

    /**
     * PUBLIC:
     * Set the receiver's insert SQL string. This allows the user to override the SQL
     * generated by TopLink, with there own SQL or procedure call. The arguments are
     * translated from the fields of the source row, through replacing the field names
     * marked by '#' with the values for those fields.
     * This is used to insert an entry into the direct table.
     * <p>Example, 'insert into RESPONS (EMP_ID, RES_DESC) values (#EMP_ID, #RES_DESC)'.
     */
    public void setInsertSQLString(String sqlString) {
        DataModifyQuery query = new DataModifyQuery();
        query.setSQLString(sqlString);
        setCustomInsertQuery(query);
    }

    /**
     * INTERNAL:
     * This cannot be used with direct collection mappings.
     */
    @Override
    public void setReferenceClass(Class referenceClass) {
        return;
    }

    @Override
    public void setReferenceClassName(String referenceClassName) {
        return;
    }

    /**
     * PUBLIC:
     * Set the name of the reference key field.
     * This is the foreign key field in the direct table referencing the primary key of the source object.
     * This method is used if the reference key consists of only a single field.
     */
    public void setReferenceKeyFieldName(String fieldName) {
        getReferenceKeyFields().addElement(new DatabaseField(fieldName));
    }

    /**
     * INTERNAL:
     * Set the reference key field names associated with the mapping.
     * These must be in-order with the sourceKeyFieldNames.
     */
    public void setReferenceKeyFieldNames(Vector fieldNames) {
        Vector fields = org.eclipse.persistence.internal.helper.NonSynchronizedVector.newInstance(fieldNames.size());
        for (Enumeration fieldNamesEnum = fieldNames.elements(); fieldNamesEnum.hasMoreElements();) {
            fields.addElement(new DatabaseField((String)fieldNamesEnum.nextElement()));
        }

        setReferenceKeyFields(fields);
    }

    /**
     * INTERNAL:
     * Set the reference fields.
     */
    public void setReferenceKeyFields(Vector<DatabaseField> aVector) {
        this.referenceKeyFields = aVector;
    }

    /**
     * INTERNAL:
     * Set the reference table.
     */
    public void setReferenceTable(DatabaseTable table) {
        referenceTable = table;
    }

    /**
     * PUBLIC:
     * Sets the selection criteria to be used as a where clause to read
     * reference objects. This criteria is automatically generated by the
     * TopLink if not explicitly specified by the user.
     */
    @Override
    public void setSelectionCriteria(Expression anExpression) {
        if (getSelectionQuery().isReadAllQuery()){
            getSelectionQuery().setSelectionCriteria(anExpression);
        } else {
            getSelectionQuery().getSQLStatement().setWhereClause(anExpression);
        }
    }

    /**
     * PUBLIC:
     * Set the reference table name.
     */
    public void setReferenceTableName(String tableName) {
        if (tableName == null) {
            setReferenceTable(null);
        } else {
            setReferenceTable(new DatabaseTable(tableName));
        }
    }

    /**
     * INTERNAL:
     * Set the container policy on the selection query for this mapping.
     */
    @Override
    protected void setSelectionQueryContainerPolicy(ContainerPolicy containerPolicy) {
        ((DataReadQuery) getSelectionQuery()).setContainerPolicy(containerPolicy);
    }

    /**
     * PUBLIC:
     * Support history on the reference table.
     */
    public void setHistoryPolicy(HistoryPolicy policy) {
        this.historyPolicy = policy;
        if (policy != null) {
            policy.setMapping(this);
        }
    }

    /**
     * PUBLIC:
     * Set the name of the session to execute the mapping's queries under.
     * This can be used by the session broker to override the default session
     * to be used for the target class.
     */
    @Override
    public void setSessionName(String name) {
        super.setSessionName(name);
        getInsertQuery().setSessionName(name);
    }

    /**
     * INTERNAL:
     * Set the source key field names associated with the mapping.
     * These must be in-order with the referenceKeyFieldNames.
     */
    public void setSourceKeyFieldNames(Vector fieldNames) {
        Vector fields = org.eclipse.persistence.internal.helper.NonSynchronizedVector.newInstance(fieldNames.size());
        for (Enumeration fieldNamesEnum = fieldNames.elements(); fieldNamesEnum.hasMoreElements();) {
            fields.addElement(new DatabaseField((String)fieldNamesEnum.nextElement()));
        }

        setSourceKeyFields(fields);
    }

    /**
     * INTERNAL:
     * Set the source fields.
     */
    public void setSourceKeyFields(Vector<DatabaseField> sourceKeyFields) {
        this.sourceKeyFields = sourceKeyFields;
    }

    /**
     * INTERNAL:
     * This method is used to store the FK fields that can be cached that correspond to noncacheable mappings
     * the FK field values will be used to re-issue the query when cloning the shared cache entity
     */
    @Override
    public void collectQueryParameters(Set<DatabaseField> cacheFields){
        for (DatabaseField field : getSourceKeyFields()) {
            cacheFields.add(field);
        }

    }

    /**
     * INTERNAL:
     * Used by AttributeLevelChangeTracking to update a changeRecord with calculated changes
     * as apposed to detected changes.  If an attribute can not be change tracked it's
     * changes can be detected through this process.
     */
    @Override
    public void calculateDeferredChanges(ChangeRecord changeRecord, AbstractSession session) {
        DirectCollectionChangeRecord collectionRecord = (DirectCollectionChangeRecord)changeRecord;
        // TODO: Handle events that fired after collection was replaced.
        compareCollectionsForChange(collectionRecord.getOriginalCollection(), collectionRecord.getLatestCollection(), collectionRecord, session);
    }

    /**
     * ADVANCED:
     * This method is used to have an object add to a collection once the changeSet is applied
     * The referenceKey parameter should only be used for direct Maps.
     */
    @Override
    public void simpleAddToCollectionChangeRecord(Object referenceKey, Object objectToAdd, ObjectChangeSet changeSet, AbstractSession session) {
        simpleAddToCollectionChangeRecord(objectToAdd, null, false, changeSet, session, true);
    }

    protected void simpleAddToCollectionChangeRecord(Object objectToAdd, Integer index, boolean isSet, ObjectChangeSet changeSet, AbstractSession session, boolean isChangeApplied) {
        DirectCollectionChangeRecord collectionChangeRecord = (DirectCollectionChangeRecord)changeSet.getChangesForAttributeNamed(getAttributeName());
        if (collectionChangeRecord == null) {
            collectionChangeRecord = new DirectCollectionChangeRecord(changeSet);
            collectionChangeRecord.setAttribute(getAttributeName());
            collectionChangeRecord.setMapping(this);
            changeSet.addChange(collectionChangeRecord);
            Object collection = getRealAttributeValueFromObject(changeSet.getUnitOfWorkClone(), session);
            if(this.listOrderField != null) {
                List originalListCopy = new ArrayList((List)collection);
                // collection already contains the added object - to bring it to the original state it should be removed
                if(index == null) {
                    originalListCopy.remove(originalListCopy.size() - 1);
                } else {
                   // intValue() is essential - otherwise invokes remove(Object)
                    originalListCopy.remove(index.intValue());
                }
                collectionChangeRecord.setOriginalCollection(originalListCopy);
                collectionChangeRecord.setLatestCollection(collection);
            } else {
                collectionChangeRecord.storeDatabaseCounts(collection, getContainerPolicy(), session);
                collectionChangeRecord.setFirstToAddAlreadyInCollection(isChangeApplied);
            }
        }
        if(!collectionChangeRecord.isDeferred() && this.listOrderField == null) {
            collectionChangeRecord.addAdditionChange(objectToAdd, 1);
        }
    }

    /**
     * ADVANCED:
     * This method is used to have an object removed from a collection once the changeSet is applied
     * The referenceKey parameter should only be used for direct Maps.
     */
    @Override
    public void simpleRemoveFromCollectionChangeRecord(Object referenceKey, Object objectToRemove, ObjectChangeSet changeSet, AbstractSession session) {
        simpleRemoveFromCollectionChangeRecord(objectToRemove, null, false, changeSet, session, true);
    }

    protected void simpleRemoveFromCollectionChangeRecord(Object objectToRemove, Integer index, boolean isSet, ObjectChangeSet changeSet, AbstractSession session, boolean isChangeApplied) {
        DirectCollectionChangeRecord collectionChangeRecord = (DirectCollectionChangeRecord)changeSet.getChangesForAttributeNamed(getAttributeName());
        if (collectionChangeRecord == null) {
            collectionChangeRecord = new DirectCollectionChangeRecord(changeSet);
            collectionChangeRecord.setAttribute(getAttributeName());
            collectionChangeRecord.setMapping(this);
            changeSet.addChange(collectionChangeRecord);
            Object collection = getRealAttributeValueFromObject(changeSet.getUnitOfWorkClone(), session);
            if(this.listOrderField != null) {
                List originalListCopy = new ArrayList((List)collection);
                // collection already doesn't contain the removed object - to bring it to the original state it should be added or set back.
                // index is not null because IndirectList does remove through indexOf.
                if(isSet) {
                    originalListCopy.set(index, objectToRemove);
                } else {
                    originalListCopy.add(index, objectToRemove);
                }
                collectionChangeRecord.setOriginalCollection(originalListCopy);
                collectionChangeRecord.setLatestCollection(collection);
            } else {
                collectionChangeRecord.storeDatabaseCounts(collection, getContainerPolicy(), session);
                collectionChangeRecord.setFirstToRemoveAlreadyOutCollection(isChangeApplied);
                if(isSet) {
                    collectionChangeRecord.setFirstToAddAlreadyInCollection(isChangeApplied);
                }
            }
        }
        if(!collectionChangeRecord.isDeferred() && this.listOrderField == null) {
            collectionChangeRecord.addRemoveChange(objectToRemove, 1);
        }
    }

    /**
     * INTERNAL:
     * Either create a new change record or update with the new value.  This is used
     * by attribute change tracking.
     * Specifically in a collection mapping this will be called when the customer
     * Set a new collection.  In this case we will need to mark the change record
     * with the new and the old versions of the collection.
     * And mark the ObjectChangeSet with the attribute name then when the changes are calculated
     * force a compare on the collections to determine changes.
     */
    @Override
    public void updateChangeRecord(Object clone, Object newValue, Object oldValue, ObjectChangeSet objectChangeSet, UnitOfWorkImpl uow) {
        DirectCollectionChangeRecord collectionChangeRecord = (DirectCollectionChangeRecord)objectChangeSet.getChangesForAttributeNamed(this.getAttributeName());
        if (collectionChangeRecord == null) {
            collectionChangeRecord = new DirectCollectionChangeRecord(objectChangeSet);
            collectionChangeRecord.setAttribute(getAttributeName());
            collectionChangeRecord.setMapping(this);
            objectChangeSet.addChange(collectionChangeRecord);
        }
        collectionChangeRecord.setIsDeferred(true);
        objectChangeSet.deferredDetectionRequiredOn(getAttributeName());
        if (collectionChangeRecord.getOriginalCollection() == null) {
            collectionChangeRecord.recreateOriginalCollection(oldValue, uow);
        }
        collectionChangeRecord.setLatestCollection(newValue);
    }

    /**
     * INTERNAL:
     * Add or removes a new value and its change set to the collection change record based on the event passed in.  This is used by
     * attribute change tracking.
     */
    @Override
    public void updateCollectionChangeRecord(CollectionChangeEvent event, ObjectChangeSet changeSet, UnitOfWorkImpl uow) {
        if (event != null ) {
            //Letting the mapping create and add the ChangeSet to the ChangeRecord rather
            // than the policy, since the policy doesn't know how to handle DirectCollectionChangeRecord.
            // if ordering is to be supported in the future, check how the method in CollectionMapping is implemented
            Object value =  event.getNewValue();

            if (event.getChangeType() == CollectionChangeEvent.ADD) {
                simpleAddToCollectionChangeRecord(value, event.getIndex(), event.isSet(), changeSet, uow, event.isChangeApplied());
            } else if (event.getChangeType() == CollectionChangeEvent.REMOVE) {
                simpleRemoveFromCollectionChangeRecord(value, event.getIndex(), event.isSet(), changeSet, uow, event.isChangeApplied());
            } else {
                throw ValidationException.wrongCollectionChangeEventType(event.getChangeType());
            }
        }
    }

    /**
     * PUBLIC:
     * It is illegal to use a Map as the container of a DirectCollectionMapping. Only
     * Collection containers are supported for DirectCollectionMappings.
     * @see org.eclipse.persistence.mappings.DirectMapMapping
     */
    @Override
    public void useMapClass(Class concreteClass, String methodName) {
        throw ValidationException.illegalUseOfMapInDirectCollection(this, concreteClass, methodName);
    }

    /**
     * INTERNAL:
     * Return the value of the reference attribute or a value holder.
     * Check whether the mapping's attribute should be optimized through batch and joining.
     * Overridden to support flashback/historical queries.
     */
    @Override
    public Object valueFromRow(AbstractRecord row, JoinedAttributeManager joinManager, ObjectBuildingQuery sourceQuery, CacheKey cacheKey, AbstractSession session, boolean isTargetProtected, Boolean[] wasCacheUsed) throws DatabaseException {
        if (this.descriptor.getCachePolicy().isProtectedIsolation()) {
            if (this.isCacheable && isTargetProtected && cacheKey != null) {
                //cachekey will be null when isolating to uow
                //used cached collection
                Object result = null;
                Object cached = cacheKey.getObject();
                if (cached != null) {
                    if (wasCacheUsed != null){
                        wasCacheUsed[0] = Boolean.TRUE;
                    }
                    return this.getAttributeValueFromObject(cached);
                }
                return result;
            } else if (!this.isCacheable && !isTargetProtected && cacheKey != null) {
                return this.indirectionPolicy.buildIndirectObject(new ValueHolder<>(null));
            }
        }
        if (row.hasSopObject()) {
            return getAttributeValueFromObject(row.getSopObject());
        }
        if (sourceQuery.isObjectLevelReadQuery() && (((ObjectLevelReadQuery)sourceQuery).isAttributeBatchRead(this.descriptor, getAttributeName())
                || (sourceQuery.isReadAllQuery() && shouldUseBatchReading()))) {
            return batchedValueFromRow(row, (ObjectLevelReadQuery)sourceQuery, cacheKey);
        }

        if (shouldUseValueFromRowWithJoin(joinManager, sourceQuery)) {
            return valueFromRowInternalWithJoin(row, joinManager, sourceQuery, cacheKey, session, isTargetProtected);
        }

        // if the query uses batch reading, return a special value holder
        // or retrieve the object from the query property.
        ReadQuery targetQuery = getSelectionQuery();

        boolean extendingPessimisticLockScope = isExtendingPessimisticLockScope(sourceQuery) && extendPessimisticLockScope == ExtendPessimisticLockScope.TARGET_QUERY;
        if ((getHistoryPolicy() != null) || (sourceQuery.getSession().getAsOfClause() != null) || ((sourceQuery.isObjectLevelReadQuery() && ((ObjectLevelReadQuery)sourceQuery).hasAsOfClause()) && (sourceQuery.shouldCascadeAllParts() || (sourceQuery.shouldCascadePrivateParts() && isPrivateOwned()) || (sourceQuery.shouldCascadeByMapping() && this.cascadeRefresh))) || extendingPessimisticLockScope) {
            targetQuery = (ReadQuery)targetQuery.clone();
            // Code copied roughly from initializeSelectionStatement.
            SQLSelectStatement statement = new SQLSelectStatement();
            statement.addTable(getReferenceTable());
            statement.addField(getDirectField().clone());
            if (isDirectMapMapping()) {
                statement.addField(((DirectMapMapping)this).getDirectKeyField().clone());
            }
            statement.setWhereClause((Expression)getSelectionCriteria().clone());
            if (sourceQuery.isObjectLevelReadQuery()) {
                statement.getBuilder().asOf(((ObjectLevelReadQuery)sourceQuery).getAsOfClause());
            }
            if (extendingPessimisticLockScope) {
                statement.setLockingClause(new ForUpdateClause(sourceQuery.getLockMode()));
            }
            if (getHistoryPolicy() != null) {
                ExpressionBuilder builder = statement.getBuilder();
                if (sourceQuery.getSession().getAsOfClause() != null) {
                    builder.asOf(sourceQuery.getSession().getAsOfClause());
                } else if (builder.getAsOfClause() == null) {
                    builder.asOf(AsOfClause.NO_CLAUSE);
                }
                Expression temporalExpression = getHistoryPolicy().additionalHistoryExpression(builder, builder);
                statement.setWhereClause(statement.getWhereClause().and(temporalExpression));
                if (builder.hasAsOfClause()) {
                    statement.getTables().set(0, getHistoryPolicy().getHistoricalTables().get(0));
                }
            }
            statement.normalize(sourceQuery.getSession(), null);
            targetQuery.setSQLStatement(statement);
        }

        return getIndirectionPolicy().valueFromQuery(targetQuery, row, sourceQuery.getSession());
    }

    /**
     * INTERNAL:
     * Checks if object is deleted from the database or not.
     */
    @Override
    public boolean verifyDelete(Object object, AbstractSession session) throws DatabaseException {
        // Row is built for translation
        if (isReadOnly()) {
            return true;
        }

        AbstractRecord row = getDescriptor().getObjectBuilder().buildRowForTranslation(object, session);
        Object value = session.executeQuery(getSelectionQuery(), row);

        return getContainerPolicy().isEmpty(value);
    }

    /**
     * INTERNAL:
     * DirectCollectionMapping contents should not be considered for addition to the UnitOfWork
     * private owned objects list for removal.
     */
    @Override
    public boolean isCandidateForPrivateOwnedRemoval() {
        return false;
    }

    /**
     * INTERNAL
     * Return true if this mapping supports cascaded version optimistic locking.
     */
    @Override
    public boolean isCascadedLockingSupported() {
        return true;
    }
}