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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
138 lines
3.5 KiB
Plaintext
138 lines
3.5 KiB
Plaintext
<!--
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doc/src/sgml/ref/savepoint.sgml
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PostgreSQL documentation
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-->
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<refentry id="sql-savepoint">
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<indexterm zone="sql-savepoint">
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<primary>SAVEPOINT</primary>
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</indexterm>
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<indexterm zone="sql-savepoint">
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<primary>savepoints</primary>
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<secondary>defining</secondary>
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</indexterm>
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<refmeta>
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<refentrytitle>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>SAVEPOINT</refname>
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<refpurpose>define a new savepoint within the current transaction</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<synopsis>
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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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<command>SAVEPOINT</command> establishes a new savepoint within
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the current transaction.
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</para>
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<para>
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A savepoint is a special mark inside a transaction that allows all commands
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that are executed after it was established to be rolled back, restoring
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the transaction state to what it was at the time of the 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>savepoint_name</replaceable></term>
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<listitem>
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<para>
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The name to give to the new savepoint.
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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-rollback-to"/> to
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rollback to a savepoint. Use <xref linkend="sql-release-savepoint"/>
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to destroy a savepoint, keeping
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the effects of commands executed after it was established.
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</para>
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<para>
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Savepoints can only be established when inside a transaction block.
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There can be multiple savepoints defined within a transaction.
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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 establish a savepoint and later undo the effects of all commands executed
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after it was established:
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<programlisting>
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BEGIN;
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INSERT INTO table1 VALUES (1);
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SAVEPOINT my_savepoint;
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INSERT INTO table1 VALUES (2);
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ROLLBACK TO SAVEPOINT my_savepoint;
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INSERT INTO table1 VALUES (3);
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COMMIT;
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</programlisting>
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The above transaction will insert the values 1 and 3, but not 2.
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</para>
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<para>
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To establish and later destroy a savepoint:
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<programlisting>
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BEGIN;
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INSERT INTO table1 VALUES (3);
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SAVEPOINT my_savepoint;
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INSERT INTO table1 VALUES (4);
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RELEASE SAVEPOINT my_savepoint;
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COMMIT;
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</programlisting>
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The above transaction will insert both 3 and 4.
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</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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SQL requires a savepoint to be destroyed automatically when another
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savepoint with the same name is established. In
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<productname>PostgreSQL</productname>, the old savepoint is kept, though only the more
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recent one will be used when rolling back or releasing. (Releasing the
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newer savepoint with <command>RELEASE SAVEPOINT</command> will cause the older one
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to again become accessible to <command>ROLLBACK TO SAVEPOINT</command> and
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<command>RELEASE SAVEPOINT</command>.) Otherwise, <command>SAVEPOINT</command> is
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fully SQL conforming.
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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-rollback-to"/></member>
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</simplelist>
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</refsect1>
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</refentry>
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