Re: array_agg() on a set larger than some arbitrary(?) limit causes runaway memory usage and eventually memory exhaustion

From: Frank van Vugt <ftm(dot)van(dot)vugt(at)foxi(dot)nl>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Tomas Vondra <tv(at)fuzzy(dot)cz>, pgsql-bugs(at)postgresql(dot)org, Valentine Gogichashvili <valgog(at)gmail(dot)com>
Subject: Re: array_agg() on a set larger than some arbitrary(?) limit causes runaway memory usage and eventually memory exhaustion
Date: 2013-11-01 12:06:20
Message-ID: 7389794.JZAAPvMp9o@techfox.foxi
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Op donderdag 31 oktober 2013 10:05:16 schreef Tom Lane:
> > It looks like this didn't go into git yet. Will it be in v9.2.6/v9.3.1?
>
> Certainly not. We can consider it for 9.4, if Tomas submits it to the
> commitfest process, but it needs review and testing. In particular
> I'm skeptical that it probably outright breaks some cases (look at
> makeMdArrayResult) and results in substantial added bloat, not savings,

Clear, please mind the fact that Tomas did point out to me that it was an
untested patch ;)

However, although the example with which I ran into this issue was a bit
contrived, the current behaviour of the array functions in terms of memory
usage does seem to be a bit greedy. So at least it _looks_ like a good idea to
want to do something about it, since triggering this issue in the real world
doesn't seem that far-fetched...

Tomas...., are you planning to (submit a patch)?

--

Best,

Frank.

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