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Add note pointing out the difference in semantics between Oracle and

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plpgsql EXCEPTION blocks.
This commit is contained in:
Tom Lane 2004-08-08 22:40:46 +00:00
parent 35a5fb6863
commit 82fde1aaa8
1 changed files with 36 additions and 3 deletions
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39
doc/src/sgml/plpgsql.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.44 2004/08/08 00:50:58 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/plpgsql.sgml,v 1.45 2004/08/08 22:40:46 tgl Exp $
-->
<chapter id="plpgsql">
@ -2647,7 +2647,7 @@ show errors;
<para>
The <literal>show errors</literal> command does not exist in
<productname>PostgreSQL</>, and is not needed since errors are
reported automatically.
reported automatically.
</para>
</listitem>
</itemizedlist>
@ -3009,7 +3009,8 @@ $$ LANGUAGE plpgsql;
<para>
The exception names supported by <application>PL/pgSQL</> are
different from Oracle's. The set of built-in exception names
is much larger (see <xref linkend="errcodes-appendix">).
is much larger (see <xref linkend="errcodes-appendix">). There
is not currently a way to declare user-defined exception names.
</para>
</callout>
</calloutlist>
@ -3032,6 +3033,38 @@ $$ LANGUAGE plpgsql;
<productname>PostgreSQL</productname>.
</para>
<sect3 id="plpgsql-porting-exceptions">
<title>Implicit Rollback after Exceptions</title>
<para>
In <application>PL/pgSQL</>, when an exception is caught by an
<literal>EXCEPTION</> clause, all database changes since the block's
<literal>BEGIN</> are automatically rolled back. That is, the behavior
is equivalent to what you'd get in Oracle with
<programlisting>
BEGIN
SAVEPOINT s1;
... code here ...
EXCEPTION
WHEN ... THEN
ROLLBACK TO s1;
... code here ...
WHEN ... THEN
ROLLBACK TO s1;
... code here ...
END;
</programlisting>
If you are translating an Oracle procedure that uses
<command>SAVEPOINT</> and <command>ROLLBACK TO</> in this style,
your task is easy: just omit the <command>SAVEPOINT</> and
<command>ROLLBACK TO</>. If you have a procedure that uses
<command>SAVEPOINT</> and <command>ROLLBACK TO</> in a different way
then some actual thought will be required.
</para>
</sect3>
<sect3>
<title><command>EXECUTE</command></title>