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Arrange for SET LOCAL's effects to persist until the end of the current top

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transaction, unless rolled back or overridden by a SET clause for the same
variable attached to a surrounding function call.  Per discussion, these
seem the best semantics.  Note that this is an INCOMPATIBLE CHANGE: in 8.0
through 8.2, SET LOCAL's effects disappeared at subtransaction commit
(leading to behavior that made little sense at the SQL level).

I took advantage of the opportunity to rewrite and simplify the GUC variable
save/restore logic a little bit.  The old idea of a "tentative" value is gone;
it was a hangover from before we had a stack.  Also, we no longer need a stack
entry for every nesting level, but only for those in which a variable's value
actually changed.
This commit is contained in:
Tom Lane
2007-09-11 00:06:42 +00:00
parent b366562e43
commit 82a47982f3
16 changed files with 814 additions and 510 deletions
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31
doc/src/sgml/ref/reset.sgml
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@@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/reset.sgml,v 1.35 2007/04/26 16:13:09 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/reset.sgml,v 1.36 2007/09/11 00:06:41 tgl Exp $
PostgreSQL documentation
-->
@@ -44,13 +44,16 @@ SET <replaceable class="parameter">configuration_parameter</replaceable> TO DEFA
have had, if no <command>SET</> had ever been issued for it in the
current session. The actual source of this value might be a
compiled-in default, the configuration file, command-line options,
or per-database or per-user default settings. See <xref
linkend="runtime-config"> for details.
or per-database or per-user default settings. This is subtly different
from defining it as <quote>the value that the parameter had at session
start</>, because if the value came from the configuration file, it
will be reset to whatever is specified by the configuration file now.
See <xref linkend="runtime-config"> for details.
</para>
<para>
See the <command>SET</> reference page for details on the
transaction behavior of <command>RESET</>.
The transactional behavior of <command>RESET</> is the same as
<command>SET</>: its effects will be undone by transaction rollback.
</para>
</refsect1>
@@ -62,8 +65,9 @@ SET <replaceable class="parameter">configuration_parameter</replaceable> TO DEFA
<term><replaceable class="PARAMETER">configuration_parameter</replaceable></term>
<listitem>
<para>
The name of a run-time parameter. See <xref linkend="sql-set"
endterm="sql-set-title"> for a list.
Name of a settable run-time parameter. Available parameters are
documented in <xref linkend="runtime-config"> and on the
<xref linkend="sql-set" endterm="sql-set-title"> reference page.
</para>
</listitem>
</varlistentry>
@@ -83,9 +87,9 @@ SET <replaceable class="parameter">configuration_parameter</replaceable> TO DEFA
<title>Examples</title>
<para>
Set the <varname>geqo</> configuration variable to its default value:
Set the <varname>timezone</> configuration variable to its default value:
<screen>
RESET geqo;
RESET timezone;
</screen>
</para>
</refsect1>
@@ -97,4 +101,13 @@ RESET geqo;
<command>RESET</command> is a <productname>PostgreSQL</productname> extension.
</para>
</refsect1>
<refsect1>
<title>See Also</title>
<simplelist type="inline">
<member><xref linkend="SQL-SET" endterm="SQL-SET-title"></member>
<member><xref linkend="SQL-SHOW" endterm="SQL-SHOW-title"></member>
</simplelist>
</refsect1>
</refentry>