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doc limitations of join fetching 

git-svn-id: https://svn.jboss.org/repos/hibernate/trunk/Hibernate3/doc@6859 1b8cb986-b30d-0410-93ca-fae66ebed9b2
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Gavin King 2005-05-22 18:11:54 +00:00
parent eb3db5e824
commit b17b9f6c99
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18
reference/en/modules/query_hql.xml
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@ -144,14 +144,24 @@
A fetch join does not usually need to assign an alias, because the associated objects A fetch join does not usually need to assign an alias, because the associated objects
should not be used in the <literal>where</literal> clause (or any other clause). Also, should not be used in the <literal>where</literal> clause (or any other clause). Also,
the associated objects are not returned directly in the query results. Instead, they may the associated objects are not returned directly in the query results. Instead, they may
be accessed via the parent object. be accessed via the parent object. The only reason we might need an alias is if we are
recursively join fetching a further collection:
</para> </para>
<programlisting><![CDATA[from Cat as cat
inner join fetch cat.mate
left join fetch cat.kittens child
left join fetch child.kittens]]></programlisting>
<para> <para>
Note that the <literal>fetch</literal> construct may not be used in queries called using Note that the <literal>fetch</literal> construct may not be used in queries called using
<literal>scroll()</literal> or <literal>iterate()</literal>. Finally, note that <literal>scroll()</literal> or <literal>iterate()</literal>. Nor should <literal>fetch</literal>
<literal>full join fetch</literal> and <literal>right join fetch</literal> are not be used together with <literal>setMaxResults()</literal> or <literal>setFirstResult()</literal>.
meaningful. It is possible to create a cartesian product by join fetching more than one collection in a
query, so take care in this case. Join fetching multiple collection roles also sometimes gives
unexpected results for bag mappings, so be careful about how you formulate your queries in this
case. Finally, note that <literal>full join fetch</literal> and <literal>right join fetch</literal>
are not meaningful.
</para> </para>
<para> <para>