From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Yeb Havinga <yebhavinga(at)gmail(dot)com> |
Subject: | Re: Transaction-lifespan memory leak with plpgsql DO blocks |
Date: | 2013-11-13 20:06:17 |
Message-ID: | 23586.1384373177@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Tue, Nov 12, 2013 at 11:18 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Or we could say "what the heck are you doing executing tens of
>> thousands of DO blocks? Make it into a real live function;
>> you'll save a lot of cycles on parsing costs." I'm not sure that
>> this is a usage pattern we ought to be optimizing for.
> I'm not volunteering to spend time fixing this, but I disagree with
> the premise that it isn't worth fixing, because I think it's a POLA
> violation.
Yeah, I'm not terribly comfortable with letting it go either. Attached
is a proposed patch. I couldn't see any nice way to do it without adding
a field to PLpgSQL_execstate, so this isn't a feasible solution for
back-patching (it'd break the plpgsql debugger). However, given the
infrequency of complaints, I think fixing it in 9.4 and up is good enough.
I checked that this eliminates the memory leak using this test case:
do $outer$
begin
for i in 1..1000000 loop
execute $e$
do $$
declare x int = 0;
begin
x := x + 1;
end;
$$;
$e$;
end loop;
end;
$outer$;
which eats a couple GB in HEAD and nothing with the patch.
The run time seems to be the same or a bit less, too.
Any objections to applying this to HEAD?
regards, tom lane
Attachment | Content-Type | Size |
---|---|---|
do-block-memory-leak-fix.patch | text/x-diff | 18.7 KB |
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