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Document that SELECT FOR UPDATE/SHARE with ORDER BY might return results

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in the incorrect order, per bug 4593.  Backpatch to 8.3.X.
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Bruce Momjian
2009-01-22 22:56:54 +00:00
parent ff8f86e7a1
commit 879d780f65
1 changed files with 17 additions and 1 deletions
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18
doc/src/sgml/ref/select.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.102 2007/11/28 15:42:31 petere Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.102.2.1 2009/01/22 22:56:54 momjian Exp $
PostgreSQL documentation
-->
@ -941,6 +941,22 @@ ROLLBACK TO s;
anymore, in which case it will not be returned.
</para>
</caution>
<caution>
<para>
Similarly, it is possible for a <command>SELECT</> command
using <literal>ORDER BY</literal> and <literal>FOR
UPDATE/SHARE</literal> to return rows out of order. This is
because <literal>ORDER BY</> is applied first. The command
orders the result, but might then block trying to obtain a lock
on one or more of the rows. Once the <literal>SELECT</>
unblocks, one of the ordered columns might have been modified
and be returned out of order. A workaround is to perform
<command>SELECT ... FOR UPDATE/SHARE</> and then <command>SELECT
... ORDER BY</>.
</para>
</caution>
</refsect2>
</refsect1>