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Since some preparation work had already been done, the only source changes left were changing empty-element tags like <xref linkend="foo"> to <xref linkend="foo"/>, and changing the DOCTYPE. The source files are still named *.sgml, but they are actually XML files now. Renaming could be considered later. In the build system, the intermediate step to convert from SGML to XML is removed. Everything is build straight from the source files again. The OpenSP (or the old SP) package is no longer needed. The documentation toolchain instructions are updated and are much simpler now. Peter Eisentraut, Alexander Lakhin, Jürgen Purtz
159 lines
4.3 KiB
Plaintext
159 lines
4.3 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. The savepoint remains valid and can be rolled back to
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again later, 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 <xref linkend="sql-release-savepoint"/> 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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