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Support UPDATE/DELETE WHERE CURRENT OF cursor_name, per SQL standard.

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Along the way, allow FOR UPDATE in non-WITH-HOLD cursors; there may once
have been a reason to disallow that, but it seems to work now, and it's
really rather necessary if you want to select a row via a cursor and then
update it in a concurrent-safe fashion.

Original patch by Arul Shaji, rather heavily editorialized by Tom Lane.
This commit is contained in:
Tom Lane
2007-06-11 01:16:30 +00:00
parent 85d72f0516
commit 6808f1b1de
30 changed files with 940 additions and 127 deletions
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27
doc/src/sgml/ref/update.sgml
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@@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.43 2007/02/01 00:28:19 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/update.sgml,v 1.44 2007/06/11 01:16:22 tgl Exp $
PostgreSQL documentation
-->
@@ -24,7 +24,7 @@ UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ [ AS ] <rep
SET { <replaceable class="PARAMETER">column</replaceable> = { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } |
( <replaceable class="PARAMETER">column</replaceable> [, ...] ) = ( { <replaceable class="PARAMETER">expression</replaceable> | DEFAULT } [, ...] ) } [, ...]
[ FROM <replaceable class="PARAMETER">fromlist</replaceable> ]
[ WHERE <replaceable class="PARAMETER">condition</replaceable> ]
[ WHERE <replaceable class="PARAMETER">condition</replaceable> | WHERE CURRENT OF <replaceable class="PARAMETER">cursor_name</replaceable> ]
[ RETURNING * | <replaceable class="parameter">output_expression</replaceable> [ AS <replaceable class="parameter">output_name</replaceable> ] [, ...] ]
</synopsis>
</refsynopsisdiv>
@@ -160,6 +160,20 @@ UPDATE [ ONLY ] <replaceable class="PARAMETER">table</replaceable> [ [ AS ] <rep
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">cursor_name</replaceable></term>
<listitem>
<para>
The name of the cursor to use in a <literal>WHERE CURRENT OF</>
condition. The row to be updated is the one most recently fetched
from this cursor. The cursor must be a simple (non-join, non-aggregate)
query on the <command>UPDATE</>'s target table.
Note that <literal>WHERE CURRENT OF</> cannot be
specified together with a boolean condition.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">output_expression</replaceable></term>
<listitem>
@@ -309,6 +323,15 @@ UPDATE wines SET stock = stock + 24 WHERE winename = 'Chateau Lafite 2003';
COMMIT;
</programlisting>
</para>
<para>
Change the <structfield>kind</> column of the table
<structname>films</structname> in the row on which the cursor
<literal>c_films</> is currently positioned:
<programlisting>
UPDATE films SET kind = 'Dramatic' WHERE CURRENT OF c_films;
</programlisting>
</para>
</refsect1>
<refsect1>