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/*
* Copyright (c) 2011, 2018 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 API and implementation
package org.eclipse.persistence.annotations;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import javax.persistence.Column;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* HashPartitioning partitions access to a database cluster by the hash of a field value from the object,
* such as the object's location, or tenant.
* The hash indexes into the list of connection pools.
* All write or read request for object's with that hash value are sent to the server.
* If a query does not include the field as a parameter, then it can either be sent
* to all server's and unioned, or left to the sesion's default behavior.
* <p>
* Partitioning can be enabled on an Entity, relationship, query, or session/persistence unit.
* Partition policies are globally named to allow reuse,
* the partitioning policy must also be set using the @Partitioned annotation to be used.
*
* @see Partitioned
* @see org.eclipse.persistence.descriptors.partitioning.HashPartitioningPolicy
* @author James Sutherland
* @since EclipseLink 2.2
*/
@Target({TYPE, METHOD, FIELD})
@Retention(RUNTIME)
public @interface HashPartitioning {
/**
* The name of the partition policy, names must be unique for the persistence unit.
*/
String name();
/**
* The database column or query parameter to partition queries by.
* This is the table column name, not the class attribute name.
* The column value must be included in the query and should normally be part of the object's Id.
* This can also be the name of a query parameter.
* If a query does not contain the field the query will not be partitioned.
*/
Column partitionColumn();
/**
* List of connection pool names to partition across.
* Defaults to all defined pools in the ServerSession.
*/
String[] connectionPools() default {};
/**
* Defines if queries that do not contain the partition field should be sent
* to every database and have the result unioned.
*/
boolean unionUnpartitionableQueries() default false;
}
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