Author: ppoddar
Date: Thu Feb 14 14:17:12 2008
New Revision: 627889
URL: http://svn.apache.org/viewvc?rev=627889&view=rev
Log:
OPENJPA-515 Add documentation for targeted query via query hints
Modified:
openjpa/trunk/openjpa-project/src/doc/manual/ref_guide_slice.xml
Modified: openjpa/trunk/openjpa-project/src/doc/manual/ref_guide_slice.xml
URL:
http://svn.apache.org/viewvc/openjpa/trunk/openjpa-project/src/doc/manual/ref_guide_slice.xml?rev=627889&r1=627888&r2=627889&view=diff
==============================================================================
--- openjpa/trunk/openjpa-project/src/doc/manual/ref_guide_slice.xml (original)
+++ openjpa/trunk/openjpa-project/src/doc/manual/ref_guide_slice.xml Thu Feb 14
14:17:12 2008
@@ -87,6 +87,19 @@
update to any of these instances is committed to the appropriate
original database slice.
</para>
+
+ <note>
+ <para>
+ You can find the original slice of an instance <code>pc</code> by
+ the static utility method
+ <methodname>SlicePersistence.getSlice(pc)</methodname>.
+ This method returns the slice identifier string associated with the
+ given <emphasis>managed</emphasis> instance. If the instance is not
+ being managed then the method return null because any unmanaged or
+ detached instance is not associated with any slice.
+ </para>
+ </note>
+
<para>
<warning>Currently, there is no provision for migrating an
existing instance from one slice to another.
@@ -129,7 +142,34 @@
The aggregate operation <code>AVG()</code> is not supported.
</warning>
</para>
+
</section>
+
+ <section><title>Targeted Query</title>
+ <para>
+ You can target the query only to a subset of slices rather than
+ all slices by setting a <emphasis>hint</emphasis>. The hint key
+ <code>openjpa.hint.slice.Target</code> is set on any query and
+ hint value is
+ comma-separated list of slice identifiers. The following
+ example shows how to target a query only to slice
<code>"One"</code>
+
+ <programlisting>
+ <![CDATA[EntityManager em = ...;
+ em.getTransaction().begin();
+ String hint = "openjpa.hint.slice.Target";
+ Query query = em.createQuery("SELECT p FROM
PObject").setHint(hint, "One");
+ List result = query.getResultList();
+ // verify that each instance is originaing from the given slice
+ for (Object pc : result) {
+ String sliceOrigin = SlicePersistence.getSlice(pc);
+ assertTrue ("One", sliceOrigin);
+ }
+ ]]>
+ </programlisting>
+ </para>
+ </section>
+
<section><title>Distributed Transaction</title>
<para>
