Re: default of max_stack_depth

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Re: default of max_stack_depth

От:
Tom Lane <tgl@sss.pgh.pa.us>
Дата:
Fujii Masao  writes:
> The document says that the max_stack_depth is 2MB by default.
> OTOH, in the source code, the variable max_stack_depth is
> initialized with 100 (kB), and guc.c also uses 100 as the
> default. Why?

The initial value needs to be small until we have been able to probe
rlimit and figure out what is safe.
		regards, tom lane

Re: default of max_stack_depth

От:
Tom Lane <tgl@sss.pgh.pa.us>
Дата:
Fujii Masao  writes:
> On Fri, Aug 6, 2010 at 11:02 PM, Tom Lane  wrote:
>> The initial value needs to be small until we have been able to probe
>> rlimit and figure out what is safe.

> Thanks! How about adding the comment about that as follows?

I added this:

   /*    * We use the hopefully-safely-small value of 100kB as the compiled-in    * default for max_stack_depth.  InitializeGUCOptions will increase it if    * possible, depending on the actual platform-specific stack limit.    */

although I don't entirely see the point.  We are certainly not going to
comment every variable whose compiled-in default gets changed by later
processing.
		regards, tom lane

default of max_stack_depth

От:
Fujii Masao <masao.fujii@gmail.com>
Дата:
Hi,

The document says that the max_stack_depth is 2MB by default.
OTOH, in the source code, the variable max_stack_depth is
initialized with 100 (kB), and guc.c also uses 100 as the
default. Why?

This seems confusing to me though I know that
InitializeGUCOptions() sets max_stack_depth to 2MB.

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center

Re: default of max_stack_depth

От:
Fujii Masao <masao.fujii@gmail.com>
Дата:
On Fri, Aug 6, 2010 at 11:02 PM, Tom Lane  wrote:
> Fujii Masao  writes:
>> The document says that the max_stack_depth is 2MB by default.
>> OTOH, in the source code, the variable max_stack_depth is
>> initialized with 100 (kB), and guc.c also uses 100 as the
>> default. Why?
>
> The initial value needs to be small until we have been able to probe
> rlimit and figure out what is safe.

Thanks! How about adding the comment about that as follows?

*** a/src/backend/utils/misc/guc.c
--- b/src/backend/utils/misc/guc.c
***************
*** 1520,1525 **** static struct config_int ConfigureNamesInt[] =
--- 1520,1531 ----               16384, 1024, MAX_KILOBYTES, NULL, NULL       },

+       /*
+        * Note: the real default of max_stack_depth is calculated in
+        * InitializeGUCOptions(). We use 100 as the sufficiently small
+        * initial value until we have been able to probe rlimit and
+        * figure out what is safe.
+        */       {               {"max_stack_depth", PGC_SUSET, RESOURCES_MEM,                       gettext_noop("Sets the maximum stack depth, in
kilobytes."),

Regards,

-- 
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center
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