12.2.2. Session scroll

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When you retrieve and update data, `flush()` and `clear()` the session regularly.
In addition, use method `scroll()` to take advantage of server-side cursors for queries that return many rows of data.

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<div class="title">Example 301. Using `scroll()`</div>
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<pre class="prettyprint highlight">`EntityManager entityManager = null;
EntityTransaction txn = null;
ScrollableResults scrollableResults = null;
try {
    entityManager = entityManagerFactory().createEntityManager();

    txn = entityManager.getTransaction();
    txn.begin();

    int batchSize = 25;

    Session session = entityManager.unwrap( Session.class );

    scrollableResults = session
        .createQuery( "select p from Person p" )
        .setCacheMode( CacheMode.IGNORE )
        .scroll( ScrollMode.FORWARD_ONLY );

    int count = 0;
    while ( scrollableResults.next() ) {
        Person Person = (Person) scrollableResults.get( 0 );
        processPerson(Person);
        if ( ++count % batchSize == 0 ) {
            //flush a batch of updates and release memory:
            entityManager.flush();
            entityManager.clear();
        }
    }

    txn.commit();
} catch (RuntimeException e) {
    if ( txn != null &amp;&amp; txn.isActive()) txn.rollback();
        throw e;
} finally {
    if (scrollableResults != null) {
        scrollableResults.close();
    }
    if (entityManager != null) {
        entityManager.close();
    }
}`</pre>
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If left unclosed by the application, Hibernate will automatically close the underlying resources (e.g. `ResultSet` and `PreparedStatement`) used internally by the `ScrollableResults` when the current transaction is ended (either commit or rollback).

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<div class="paragraph">

However, it is good practice to close the `ScrollableResults` explicitly.

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<div class="sect3">