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<!--
doc/src/sgml/ref/rollback_to.sgml
PostgreSQL documentation
-->
<refentry id="sql-rollback-to">
<indexterm zone="sql-rollback-to">
<primary>ROLLBACK TO SAVEPOINT</primary>
</indexterm>
<indexterm zone="sql-rollback-to">
<primary>savepoints</primary>
<secondary>rolling back</secondary>
</indexterm>
<refmeta>
<refentrytitle>ROLLBACK TO SAVEPOINT</refentrytitle>
<manvolnum>7</manvolnum>
<refmiscinfo>SQL - Language Statements</refmiscinfo>
</refmeta>
<refnamediv>
<refname>ROLLBACK TO SAVEPOINT</refname>
<refpurpose>roll back to a savepoint</refpurpose>
</refnamediv>
<refsynopsisdiv>
<synopsis>
ROLLBACK [ WORK | TRANSACTION ] TO [ SAVEPOINT ] <replaceable>savepoint_name</replaceable>
</synopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para>
Roll back all commands that were executed after the savepoint was
established. The savepoint remains valid and can be rolled back to
again later, if needed.
</para>
<para>
<command>ROLLBACK TO SAVEPOINT</command> implicitly destroys all savepoints that
were established after the named savepoint.
</para>
</refsect1>
<refsect1>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="parameter">savepoint_name</replaceable></term>
<listitem>
<para>
The savepoint to roll back to.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1>
<title>Notes</title>
<para>
Use <link linkend="sql-release-savepoint"><command>RELEASE SAVEPOINT</command></link> to destroy a savepoint
without discarding the effects of commands executed after it was
established.
</para>
<para>
Specifying a savepoint name that has not been established is an error.
</para>
<para>
Cursors have somewhat non-transactional behavior with respect to
savepoints. Any cursor that is opened inside a savepoint will be closed
when the savepoint is rolled back. If a previously opened cursor is
affected by a <command>FETCH</command> or <command>MOVE</command> command inside a
savepoint that is later rolled back, the cursor remains at the
position that <command>FETCH</command> left it pointing to (that is, the cursor
motion caused by <command>FETCH</command> is not rolled back).
Closing a cursor is not undone by rolling back, either.
However, other side-effects caused by the cursor's query (such as
side-effects of volatile functions called by the query) <emphasis>are</emphasis>
rolled back if they occur during a savepoint that is later rolled back.
A cursor whose execution causes a transaction to abort is put in a
cannot-execute state, so while the transaction can be restored using
<command>ROLLBACK TO SAVEPOINT</command>, the cursor can no longer be used.
</para>
</refsect1>
<refsect1>
<title>Examples</title>
<para>
To undo the effects of the commands executed after <literal>my_savepoint</literal>
was established:
<programlisting>
ROLLBACK TO SAVEPOINT my_savepoint;
</programlisting>
</para>
<para>
Cursor positions are not affected by savepoint rollback:
<programlisting>
BEGIN;
DECLARE foo CURSOR FOR SELECT 1 UNION SELECT 2;
SAVEPOINT foo;
FETCH 1 FROM foo;
?column?
----------
1
ROLLBACK TO SAVEPOINT foo;
FETCH 1 FROM foo;
?column?
----------
2
COMMIT;
</programlisting></para>
</refsect1>
<refsect1>
<title>Compatibility</title>
<para>
The <acronym>SQL</acronym> standard specifies that the key word
<literal>SAVEPOINT</literal> is mandatory, but <productname>PostgreSQL</productname>
and <productname>Oracle</productname> allow it to be omitted. SQL allows
only <literal>WORK</literal>, not <literal>TRANSACTION</literal>, as a noise word
after <literal>ROLLBACK</literal>. Also, SQL has an optional clause
<literal>AND [ NO ] CHAIN</literal> which is not currently supported by
<productname>PostgreSQL</productname>. Otherwise, this command conforms to
the SQL standard.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="sql-begin"/></member>
<member><xref linkend="sql-commit"/></member>
<member><xref linkend="sql-release-savepoint"/></member>
<member><xref linkend="sql-rollback"/></member>
<member><xref linkend="sql-savepoint"/></member>
</simplelist>
</refsect1>
</refentry>
|
