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Java Persistence API (JPA) Extensions Reference for EclipseLink, Release 2.4
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@HashPartitioning

Use @HashPartitioning to partition 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.


Annotation Elements

Table 2-25 describes this annotation's elements.

Table 2-25 @HashPartitioning Annotation Elements

Annotation Element Description Default

name

(Required) The name of the partition policy. The name must be unique within the persistence unit.


partitionColumn

(Required) The database column or query parameter by which to partition queries.


connectionPools

(Optional) List of connection pool names across which to partition.

All defined pools in the ServerSession

unionUnpartitionableQueries

(Optional) Specify if queries that do not contain the partition hash should be sent to every database and union the result.

False



Usage

All write or read requests for objects with the hash value are sent to the server. Queries that do not include the field as a parameter will be:

You can enable partitioning on an Entity, relationship, query, or session/persistence unit. Partition policies are globally named (to allow reuse) and must set using the @Partitioned annotation.

The persistence unit properties support adding named connection pools in addition to the existing configuration for read/write/sequence. A named connection pool must be defined for each node in the database cluster.

If a transaction modifies data from multiple partitions, you should use JTA to ensure proper two-phase commit of the data. You can also configure an exclusive connection in the EntityManager to ensure that only a single node is used for a single transaction.


Examples

See "@Partitioned" for an example of partitioning with EclipseLink.


See Also

For more information, see:

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