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Difference between revisions of "EclipseLink/UserGuide/JPA/Basic JPA Development/Caching/Query Options"
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Entities can be accessed through JPA using either <tt>find()</tt> or queries. <tt>find()</tt> will first check the persistence context cache (L1) for the Id, if the object is not found it will check the shared persistence unit cache (L2), if the object is still not found it will access the database. By default all queries will access the database, unless querying by Id or by cache indexed fields. Once the query retrieves the rows from the database, it will resolve each row with the cache. If the object is already in the cache, then the row will be discarded, and the object will be used. If the object is not in the shared cache, then it will be built from the row and put into the shared cache. A copy will also be put in the persistence context cache and returned as the query result. | Entities can be accessed through JPA using either <tt>find()</tt> or queries. <tt>find()</tt> will first check the persistence context cache (L1) for the Id, if the object is not found it will check the shared persistence unit cache (L2), if the object is still not found it will access the database. By default all queries will access the database, unless querying by Id or by cache indexed fields. Once the query retrieves the rows from the database, it will resolve each row with the cache. If the object is already in the cache, then the row will be discarded, and the object will be used. If the object is not in the shared cache, then it will be built from the row and put into the shared cache. A copy will also be put in the persistence context cache and returned as the query result. | ||
− | This is the general process, but it differs if the transaction is <i>dirty</i>. If the transaction is diry then the shared cache will be ignored and objects will be built directly | + | This is the general process, but it differs if the transaction is <i>dirty</i>. If the transaction is diry then the shared persistence unit cache will be ignored and objects will be built directly into the persistence context cache. |
A transaction is considered dirty in the following circumstances: | A transaction is considered dirty in the following circumstances: | ||
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Entities can also be configured to be isolated, or non cacheable, in which case they will never be placed in the shared cache (see [[EclipseLink/UserGuide/JPA/Basic JPA Development/Caching/Shared and Isolated|Shared, Isolated, Protected, Weak and Read-only Cache]]). | Entities can also be configured to be isolated, or non cacheable, in which case they will never be placed in the shared cache (see [[EclipseLink/UserGuide/JPA/Basic JPA Development/Caching/Shared and Isolated|Shared, Isolated, Protected, Weak and Read-only Cache]]). | ||
− | == | + | ==JPA Cache Query Hints== |
− | + | JPA 2.0 defines the following query hints to configure a queries interaction with the shared cache: | |
− | + | ||
{{EclipseLink_HintTable | {{EclipseLink_HintTable | ||
− | |caption= | + | |caption=JPA Cache Query Hints |
|content= | |content= | ||
<tr> | <tr> | ||
− | <td><tt> | + | <td><tt>javax.persistence.cache.retrieveMode</tt></td> |
− | <td> | + | <td>Configure how the shared cache is accessed. |
− | + | Valid values are defined in <tt>CacheRetrieveMode</tt> enum: | |
− | + | * <tt>BYPASS</tt> : Ignore the shared persistence unit cache, and build the object directly into the persistence context cache. | |
− | + | * <tt>USE</tt> : Use the shared persistence unit cache. If the object is already in the shared cache, use the object. | |
− | + | </td> | |
− | + | <td><tt>USE</tt></td> | |
− | + | ||
− | + | ||
− | <td><tt> | + | |
<td>Optional</td> | <td>Optional</td> | ||
</tr> | </tr> | ||
<tr> | <tr> | ||
− | <td><tt> | + | <td><tt>javax.persistence.cache.storeMode</tt></td> |
− | <td> | + | <td>Configure how the shared cache is modified. |
− | + | Valid values are defined in <tt>CacheStoreMode</tt> enum: | |
− | + | * <tt>BYPASS</tt> : Do not put any object build from the row data into the shared cache. | |
− | + | * <tt>REFRESH</tt> : If the object is in the shared cache, refresh its data from the database row data. | |
− | + | * <tt>USE</tt> : If the object is not in the shared cache, then build it from the database row data and put it into the shared cache. | |
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</tr> | </tr> | ||
}} | }} | ||
+ | |||
+ | ======''Refresh query hint example''====== | ||
+ | <source lang="java"> | ||
+ | Query query = em.createQuery("Select e from Employee e where e.address.city = :city"); | ||
+ | query.setHint("javax.persistence.cache.storeMode, REFRESH); | ||
+ | query.setParameter("city", "Ottawa"); | ||
+ | List<Employee> employees = query.getResultList(); | ||
+ | </source> | ||
======''In-memory query example''====== | ======''In-memory query example''====== |
Revision as of 14:07, 29 May 2012
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Contents
Query Options and In-memory Querying
JPA defines standard query hints for configuring how a query interacts with the shared persistence unit cache (L2). EclipseLink also provides some additional query hints for configuring the cache usage.
Entities can be accessed through JPA using either find() or queries. find() will first check the persistence context cache (L1) for the Id, if the object is not found it will check the shared persistence unit cache (L2), if the object is still not found it will access the database. By default all queries will access the database, unless querying by Id or by cache indexed fields. Once the query retrieves the rows from the database, it will resolve each row with the cache. If the object is already in the cache, then the row will be discarded, and the object will be used. If the object is not in the shared cache, then it will be built from the row and put into the shared cache. A copy will also be put in the persistence context cache and returned as the query result.
This is the general process, but it differs if the transaction is dirty. If the transaction is diry then the shared persistence unit cache will be ignored and objects will be built directly into the persistence context cache.
A transaction is considered dirty in the following circumstances:
- A flush() has written changes to the database.
- A pessimistic lock query has been executed.
- An update or delete query has been executed.
- A native SQL query has been executed.
- This persistence unit property "eclipselink.transaction.join-existing" is used.
- The JDBC connection has been unwrapped from the EntityManager.
- The UnitOfWork API beginEarlyTransaction has been called.
Entities can also be configured to be isolated, or non cacheable, in which case they will never be placed in the shared cache (see Shared, Isolated, Protected, Weak and Read-only Cache).
JPA Cache Query Hints
JPA 2.0 defines the following query hints to configure a queries interaction with the shared cache:
Hint | Description | Default | Required? |
---|---|---|---|
javax.persistence.cache.retrieveMode | Configure how the shared cache is accessed.
Valid values are defined in CacheRetrieveMode enum:
|
USE | Optional |
javax.persistence.cache.storeMode | Configure how the shared cache is modified.
Valid values are defined in CacheStoreMode enum:
|
Refresh query hint example
Query query = em.createQuery("Select e from Employee e where e.address.city = :city"); query.setHint("javax.persistence.cache.storeMode, REFRESH); query.setParameter("city", "Ottawa"); List<Employee> employees = query.getResultList();
In-memory query example
Query query = em.createQuery("Select e from Employee e where e.firstName like :firstName and e.lastName like :lastName"); query.setParameter("firstName", "B%"); query.setParameter("lastName", "S%"); List<Employee> employees = query.getResultList();