com.github.helenusdriver.persistence.PartitionKey Maven / Gradle / Ivy
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/*
* Copyright (C) 2015-2015 The Helenus Driver Project Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.github.helenusdriver.persistence;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Repeatable;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.Set;
import com.github.helenusdriver.annotation.Keyable;
/**
* The PartitionKey annotation indicates the column is a partition
* key. The partition key determines on which nodes data is stored.
*
* It is also possible to specify compound partition keys by annotating
* multiple fields or properties with the PartitionKey annotation.
*
* Special support is given to a partition key defined as {@link Set}. Using
* such a multi-partition key enables querying for any of its elements to
* retrieve the object from the database. Underneath the table, in addition to
* saving the key as a set in the defined column, the driver will also create
* another column of the element type as the actual partition key and create
* multiple entries in the table; one per element of the multi-key.
*
* @copyright 2015-2015 The Helenus Driver Project Authors
*
* @author The Helenus Driver Project Authors
* @version 1 - Jan 15, 2015 - paouelle - Creation
*
* @since 1.0
*/
@Target({ElementType.METHOD, ElementType.FIELD})
@Retention(RetentionPolicy.RUNTIME)
@Repeatable(PartitionKeys.class)
@Keyable("table")
@Documented
public @interface PartitionKey {
/**
* The name of the table as defined in {@link Table#name} this partition key is
* associated with.
*
* By default, if none specified, the column will be considered a partition
* key for all tables defined by the entity unless otherwise overridden.
*
* @author paouelle
*
* @return the name of the table this partition key is assocaited with
*/
String table() default Table.ALL;
}