| 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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| Lists: | pgsql-hackers |
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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