6.5. Flush operation order

<div class="paragraph">

From a database perspective, a row state can be altered using either an `INSERT`, an `UPDATE` or a `DELETE` statement.
Because entity state changes are automatically converted to SQL statements, it&#8217;s important to know which entity actions are associated to a given SQL statement.

</div>
<div class="dlist">
<dl>
<dt class="hdlist1">`INSERT`</dt>
<dd>

The `INSERT` statement is generated either by the `EntityInsertAction` or `EntityIdentityInsertAction`. These actions are scheduled by the `persist` operation, either explicitly or through cascading the `PersistEvent` from a parent to a child entity.

</dd>
<dt class="hdlist1">`DELETE`</dt>
<dd>

The `DELETE` statement is generated by the `EntityDeleteAction` or `OrphanRemovalAction`.

</dd>
<dt class="hdlist1">`UPDATE`</dt>
<dd>

The `UPDATE` statement is generated by `EntityUpdateAction` during flushing if the managed entity has been marked modified. The dirty checking mechanism is responsible for determining if a managed entity has been modified since it was first loaded.

</dd>
</dl>
</div>
<div class="paragraph">

Hibernate does not execute the SQL statements in the order of their associated entity state operations.

</div>
<div class="paragraph">

To visualize how this works, consider the following example:

</div>
<div id="flushing-order-example" class="exampleblock">
<div class="title">Example 272. Flush operation order</div>
<div class="content">
<div class="listingblock">
<div class="content">
<pre class="prettyprint highlight">`Person person = entityManager.find( Person.class, 1L);
entityManager.remove(person);

Person newPerson = new Person( );
newPerson.setId( 2L );
newPerson.setName( "John Doe" );
entityManager.persist( newPerson );`</pre>
</div>
</div>
<div class="listingblock">
<div class="content">
<pre class="prettyprint highlight">`INSERT INTO Person (name, id)
VALUES ('John Doe', 2L)

DELETE FROM Person WHERE id = 1`</pre>
</div>
</div>
</div>
</div>
<div class="paragraph">

Even if we removed the first entity and then persist a new one, Hibernate is going to execute the `DELETE` statement after the `INSERT`.

</div>
<div class="admonitionblock tip">
<table>
<tr>
<td class="icon">

</td>
<td class="content">
<div class="paragraph">

The order in which SQL statements are executed is given by the `ActionQueue` and not by the order in which entity state operations have been previously defined.

</div>
</td>
</tr>
</table>
</div>
<div class="paragraph">

The `ActionQueue` executes all operations in the following order:

</div>
<div class="olist arabic">

1. OrphanRemovalAction
2. EntityInsertAction or EntityIdentityInsertAction
3. EntityUpdateAction
4. CollectionRemoveAction
5. CollectionUpdateAction
6. CollectionRecreateAction
7. EntityDeleteAction </div> </div> </div> </div>