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