From: Bruce Momjian <bruce@momjian.us>
Date: Fri, 22 Apr 2005 04:20:44 +0000 (+0000)
Subject: Remove pre-7.3 mention that FOR UPDATE can be before LIMIT.
X-Git-Tag: REL8_1_0BETA1~969
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d76f279a55203472302944ab592f6e681b367c48;p=postgresql

Remove pre-7.3 mention that FOR UPDATE can be before LIMIT.

Document that FOR UPDATE and LIMIT together can return fewer rows that
LIMIT specifies, and why.
---

diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 9044adfa8c..444b72cebe 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.83 2005/04/08 00:59:58 neilc Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/select.sgml,v 1.84 2005/04/22 04:20:44 momjian Exp $
 PostgreSQL documentation
 -->
 
@@ -830,11 +830,13 @@ FOR UPDATE [ OF <replaceable class="parameter">table_name</replaceable> [, ...]
    </para>
 
    <para>
-    <literal>FOR UPDATE</literal> may appear before
-    <literal>LIMIT</literal> for compatibility with
-    <productname>PostgreSQL</productname> versions before 7.3.  It
-    effectively executes after <literal>LIMIT</literal>, however, and
-    so that is the recommended place to write it.
+    It is possible for a <command>SELECT</> command using both 
+    <literal>LIMIT</literal> and  <literal>FOR UPDATE</literal> 
+    clauses to return fewer rows than specified by <literal>LIMIT</literal>.
+    This is because <literal>LIMIT</> selects a number of rows,
+    but might then block requesting a <literal>FOR UPDATE</literal> lock.
+    Once the <literal>SELECT</> unblocks, the query qualifiation might not
+    be met and the row not be returned by <literal>SELECT</>.
    </para>
   </refsect2>
  </refsect1>