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Replace max_expr_depth parameter with a max_stack_depth parameter that

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is measured in kilobytes and checked against actual physical execution
stack depth, as per my proposal of 30-Dec.  This gives us a fairly
bulletproof defense against crashing due to runaway recursive functions.
This commit is contained in:
Tom Lane
2004-03-24 22:40:29 +00:00
parent a09b9a36d3
commit 8899a2aba9
13 changed files with 157 additions and 79 deletions
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34
doc/src/sgml/runtime.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.253 2004/03/24 03:48:41 neilc Exp $
$PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.254 2004/03/24 22:40:28 tgl Exp $
-->
<Chapter Id="runtime">
@ -889,6 +889,26 @@ SET ENABLE_SEQSCAN TO OFF;
</listitem>
</varlistentry>
<varlistentry id="guc-max-stack-depth" xreflabel="max_stack_depth">
<term><varname>max_stack_depth</varname> (<type>integer</type>)</term>
<listitem>
<para>
Specifies the maximum safe depth of the server's execution stack.
The ideal setting for this parameter is the actual stack size limit
enforced by the kernel (as set by <literal>ulimit -s</> or local
equivalent), less a safety margin of a megabyte or so. The safety
margin is needed because the stack depth is not checked in every
routine in the server, but only in key potentially-recursive routines
such as expression evaluation. Setting the parameter higher than
the actual kernel limit will mean that a runaway recursive function
can crash an individual backend process. The default setting is
2048 KB (two megabytes), which is conservatively small and unlikely
to risk crashes. However, it may be too small to allow execution
of complex functions.
</para>
</listitem>
</varlistentry>
</variablelist>
</sect3>
<sect3 id="runtime-config-resource-fsm">
@ -2573,18 +2593,6 @@ dynamic_library_path = '/usr/local/lib/postgresql:/home/my_project/lib:$libdir'
</listitem>
</varlistentry>
<varlistentry id="guc-max-expr-depth" xreflabel="max_expr_depth">
<term><varname>max_expr_depth</varname> (<type>integer</type>)</term>
<listitem>
<para>
Sets the maximum expression nesting depth of the parser. The
default value of 10000 is high enough for any normal query,
but you can raise it if needed. (But if you raise it too high,
you run the risk of server crashes due to stack overflow.)
</para>
</listitem>
</varlistentry>
</variablelist>
</sect3>
</sect2>