foundation/org.eclipse.persistence.core/src/main/java/org/eclipse/persistence/annotations/BatchFetch.java

/*
 * Copyright (c) 2011, 2020 Oracle and/or its affiliates. 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:
//     James Sutherland - initial implementation
package org.eclipse.persistence.annotations;

import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * A BatchFetch annotation can be used on any relationship mapping,
 * (OneToOne, ManyToOne, OneToMany, ManyToMany, ElementCollection, BasicCollection, BasicMap).
 * It allows the related objects to be batch read in a single query.
 * Batch fetching can also be set at the query level, and it is
 * normally recommended to do so as all queries may not require batching.
 *
 * @author James Sutherland
 * @since EclipseLink 2.1
 */
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface BatchFetch {
    /**
     * (Optional) The type of batch-fetch to use.
     * Either JOIN, EXISTS or IN.
     * JOIN is the default.
     */
    BatchFetchType value() default BatchFetchType.JOIN;

    /**
     * Define the default batch fetch size.
     * This is only used for IN type batch reading and defines
     * the number of keys used in each IN clause.
     * The default size is 256, or the query's pageSize for cursor queries.
     */
    int size() default -1;
}