Re: Less than ideal error reporting in pg_stat_statements

From: Peter Geoghegan <pg(at)heroku(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Less than ideal error reporting in pg_stat_statements
Date: 2015-10-04 23:29:01
Message-ID: CAM3SWZS2ysuMRJduTtBJkDOm8u3MAOgksLFn=2UgC8T-QJc7vw@mail.gmail.com
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On Sun, Oct 4, 2015 at 3:16 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Peter Geoghegan <pg(at)heroku(dot)com> writes:
>> To be clear: I wasn't sure why you though I falsely count entries with
>> dropped texts within entry_dealloc().
>
> In the existing^H^H^Hprevious code, dropped-text entries would essentially
> act as length-zero summands in the average calculation, whereas I think
> we agree that they ought to be ignored; otherwise they decrease the
> computed mean and thereby increase the probability of (useless) GC cycles.
> In the worst case where the hashtable is mostly dropped-text entries,
> which would for instance be the prevailing situation shortly after a GC
> failure, we'd be calculating ridiculously small mean values and that'd
> prompt extra GC cycles no?

Yes, but my patch changed that, too. I suggested that first.

--
Peter Geoghegan

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