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RELEASE SAVEPOINT to make an older savepoint with the same name accessible. It's also possible to implicitly release the savepoint by rolling back to an earlier savepoint, but mentioning that too would make the note just more verbose and confusing.
138 lines
3.6 KiB
Plaintext
138 lines
3.6 KiB
Plaintext
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$PostgreSQL: pgsql/doc/src/sgml/ref/savepoint.sgml,v 1.8 2010/05/27 06:25:32 heikki Exp $
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PostgreSQL documentation
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-->
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<refentry id="SQL-SAVEPOINT">
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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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<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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<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</>, 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</> will cause the older one
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to again become accessible to <command>ROLLBACK TO SAVEPOINT</> and
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<command>RELEASE SAVEPOINT</>.) 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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