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Re: pgbench internal contention

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: pgbench internal contention
Date: 2011-08-03 02:27:53
Message-ID: CA+TgmoZSknHUeXXD8P4NJhkLVHkR0WZGVCXeR8zOWTXKAym6QA@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, Aug 2, 2011 at 8:44 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>>> If you want erand48_r, best to provide that API, not kluge up some
>>> other functions.
>
>> ...because erand48() is a GNU extension with a stupid API.
>
> I assume you mean erand48_r, there, because erand48 is pretty standard.

Yes.

>> I don't
>> see much value in supporting that, on both counts.  We're going to end
>> up with the built-in erand48_r() on precisely those systems that use
>> glibc, and our own everywhere else.  For the 25 SLOCs it's going cost
>> us, I'd rather use the same code everywhere.
>
> Maybe.  But if that's the approach we want to use, let's just call it
> pg_erand48 in the code, and dispense with the alias macros as well as
> all vestiges of configure support.

Works for me.  Just to confirm, that means we'd also change GEQO to
use pg_erand48().

> BTW, as far as the original plan of using random_r is concerned, how
> did you manage to not run into this?
> http://sourceware.org/bugzilla/show_bug.cgi?id=3662
> I just wasted half an hour on that stupidity in an unrelated context...

Good grief.  It's hard to imagine a more user-hostile attitude than
the one taken there.  I did run into that precise issue, but managed
to stumble on what is apparently the officially sanctioned method of
working around it - viz, zeroing the state array.  However, that bug
report is a pretty compelling argument for the position that expecting
any of the GNU blah_r() functions to behave halfway sanely or be
properly documented is a pipe dream.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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