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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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10
doc/src/sgml/ref/create_function.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.77 2007/09/03 18:46:29 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/create_function.sgml,v 1.78 2007/09/11 00:06:41 tgl Exp $
-->
<refentry id="SQL-CREATEFUNCTION">
@ -475,11 +475,11 @@ CREATE FUNCTION foo(int, out text) ...
</para>
<para>
If any <literal>SET</> clauses are attached to a function, then
If a <literal>SET</> clause is attached to a function, then
the effects of a <command>SET LOCAL</> command executed inside the
function are restricted to the function: the configuration parameter's
value is restored at function exit. This is true even for parameters
not mentioned in the <literal>SET</> clause(s). However, an ordinary
function for the same variable are restricted to the function: the
configuration parameter's prior value is still restored at function exit.
However, an ordinary
<command>SET</> command (without <literal>LOCAL</>) overrides the
<literal>SET</> clause, much as it would do for a previous <command>SET
LOCAL</> command: the effects of such a command will persist after

5
doc/src/sgml/ref/prepare_transaction.sgml
View File

@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/prepare_transaction.sgml,v 1.5 2006/09/16 00:30:19 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/prepare_transaction.sgml,v 1.6 2007/09/11 00:06:41 tgl Exp $
PostgreSQL documentation
-->
@ -94,7 +94,8 @@ PREPARE TRANSACTION <replaceable class="PARAMETER">transaction_id</replaceable>
</para>
<para>
If the transaction modified any run-time parameters with <command>SET</>,
If the transaction modified any run-time parameters with <command>SET</>
(without the <literal>LOCAL</> option),
those effects persist after <command>PREPARE TRANSACTION</>, and will not
be affected by any later <command>COMMIT PREPARED</command> or
<command>ROLLBACK PREPARED</command>. Thus, in this one respect

31
doc/src/sgml/ref/reset.sgml
View File

@ -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>

57
doc/src/sgml/ref/set.sgml
View File

@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/set.sgml,v 1.90 2006/09/22 16:20:00 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/set.sgml,v 1.91 2007/09/11 00:06:41 tgl Exp $
PostgreSQL documentation
-->
@ -40,13 +40,10 @@ SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
</para>
<para>
If <command>SET</command> or <command>SET SESSION</command> is issued
within a transaction that is later aborted, the effects of the
If <command>SET</command> (or equivalently <command>SET SESSION</command>)
is issued within a transaction that is later aborted, the effects of the
<command>SET</command> command disappear when the transaction is rolled
back. (This behavior represents a change from
<productname>PostgreSQL</productname> versions prior to 7.3, where
the effects of <command>SET</command> would not roll back after a later
error.) Once the surrounding transaction is committed, the effects
back. Once the surrounding transaction is committed, the effects
will persist until the end of the session, unless overridden by another
<command>SET</command>.
</para>
@ -59,6 +56,36 @@ SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
seen until the end of the transaction, but afterwards (if the transaction
is committed) the <command>SET</command> value will take effect.
</para>
<para>
The effects of <command>SET</command> or <command>SET LOCAL</command> are
also canceled by rolling back to a savepoint that is earlier than the
command.
</para>
<para>
If <command>SET LOCAL</command> is used within a function that has a
<literal>SET</> option for the same variable (see
<xref linkend="sql-createfunction" endterm="sql-createfunction-title">),
the effects of the <command>SET LOCAL</command> command disappear at
function exit; that is, the value in effect when the function was called is
restored anyway. This allows <command>SET LOCAL</command> to be used for
dynamic or repeated changes of a parameter within a function, while still
having the convenience of using the <literal>SET</> option to save and
restore the caller's value. However, a regular <command>SET</> command
overrides any surrounding function's <literal>SET</> option; its effects
will persist unless rolled back.
</para>
<note>
<para>
In <productname>PostgreSQL</productname> versions 8.0 through 8.2,
the effects of a <command>SET LOCAL</command> would be canceled by
releasing an earlier savepoint, or by successful exit from a
<application>PL/pgSQL</application> exception block. This behavior
has been changed because it was deemed unintuitive.
</para>
</note>
</refsect1>
<refsect1>
@ -106,8 +133,11 @@ SET [ SESSION | LOCAL ] TIME ZONE { <replaceable class="PARAMETER">timezone</rep
<para>
New value of parameter. Values can be specified as string
constants, identifiers, numbers, or comma-separated lists of
these. <literal>DEFAULT</literal> can be used to specify
resetting the parameter to its default value.
these, as appropriate for the particular parameter.
<literal>DEFAULT</literal> can be written to specify
resetting the parameter to its default value (that is, whatever
value it would have had if no <command>SET</> had been executed
in the current session).
</para>
</listitem>
</varlistentry>
@ -200,7 +230,9 @@ SELECT setseed(<replaceable>value</replaceable>);
<term><literal>DEFAULT</literal></term>
<listitem>
<para>
Set the time zone to your local time zone (the one that
Set the time zone to your local time zone (that is, the
server's default value of <varname>timezone</>; if this
has not been explicitly set anywhere, it will be the zone that
the server's operating system defaults to).
</para>
</listitem>
@ -221,7 +253,10 @@ SELECT setseed(<replaceable>value</replaceable>);
<para>
The function <function>set_config</function> provides equivalent
functionality. See <xref linkend="functions-admin">.
functionality; see <xref linkend="functions-admin">.
Also, it is possible to UPDATE the
<link linkend="view-pg-settings"><structname>pg_settings</structname></link>
system view to perform the equivalent of <command>SET</>.
</para>
</refsect1>

10
doc/src/sgml/ref/show.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.42 2006/09/16 00:30:20 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.43 2007/09/11 00:06:41 tgl Exp $
PostgreSQL documentation
-->
@ -36,7 +36,7 @@ SHOW ALL
the <envar>PGOPTIONS</envar> environmental variable (when using
<application>libpq</> or a <application>libpq</>-based
application), or through command-line flags when starting the
<command>postgres</command>. See <xref
<command>postgres</command> server. See <xref
linkend="runtime-config"> for details.
</para>
</refsect1>
@ -130,7 +130,11 @@ SHOW ALL
<para>
The function <function>current_setting</function> produces
equivalent output. See <xref linkend="functions-admin">.
equivalent output; see <xref linkend="functions-admin">.
Also, the
<link linkend="view-pg-settings"><structname>pg_settings</structname></link>
system view produces the same information.
</para>
</refsect1>