5.12. Evicting entities

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When the `flush()` method is called, the state of the entity is synchronized with the database.
If you do not want this synchronization to occur, or if you are processing a huge number of objects and need to manage memory efficiently,
the `evict()` method can be used to remove the object and its collections from the first-level cache.

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<div id="caching-management-jpa-detach-example" class="exampleblock">
<div class="title">Example 257. Detaching an entity from the `EntityManager`</div>
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<pre class="prettyprint highlight">`for(Person person : entityManager.createQuery("select p from Person p", Person.class)
        .getResultList()) {
    dtos.add(toDTO(person));
    entityManager.detach( person );
}`</pre>
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<div id="caching-management-native-evict-example" class="exampleblock">
<div class="title">Example 258. Evicting an entity from the Hibernate `Session`</div>
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<pre class="prettyprint highlight">`Session session = entityManager.unwrap( Session.class );
for(Person person : (List&lt;Person&gt;) session.createQuery("select p from Person p").list()) {
    dtos.add(toDTO(person));
    session.evict( person );
}`</pre>
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To detach all entities from the current persistence context, both the `EntityManager` and the Hibernate `Session` define a `clear()` method.

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<div id="caching-management-clear-example" class="exampleblock">
<div class="title">Example 259. Clearing the persistence context</div>
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<pre class="prettyprint highlight">`entityManager.clear();

session.clear();`</pre>
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To verify if an entity instance is currently attached to the running persistence context, both the `EntityManager` and the Hibernate `Session` define a `contains(Object entity)` method.

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<div id="caching-management-contains-example" class="exampleblock">
<div class="title">Example 260. Verify if an entity is contained in a persistence context</div>
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<pre class="prettyprint highlight">`entityManager.contains( person );

session.contains( person );`</pre>
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