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1ff01b3902
IDs in SGML are case insensitive, and we have accumulated a mix of upper and lower case IDs, including different variants of the same ID. In XML, these will be case sensitive, so we need to fix up those differences. Going to all lower case seems most straightforward, and the current build process already makes all anchors and lower case anyway during the SGML->XML conversion, so this doesn't create any difference in the output right now. A future XML-only build process would, however, maintain any mixed case ID spellings in the output, so that is another reason to clean this up beforehand. Author: Alexander Lakhin <exclusion@gmail.com>
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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