Re: Performance problem on 2 PG versions on same query - Mailing list pgsql-general

From Rémy-Christophe Schermesser
Subject Re: Performance problem on 2 PG versions on same query
Date
Msg-id CAJDhA5wcDAEC+z_HKYv4Pn-H=SLLsxLnHEvCrAGHF1RE_snHog@mail.gmail.com
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In response to Re: Performance problem on 2 PG versions on same query  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
Thank you very much for the insights (and how to read correctly a explain :)).
There is a difference in data between the 2 databases, crons where running on one and not the other.

But your insights enabled us to dive deeper, thanks !

2014-11-05 18:30 GMT+01:00 Tom Lane <tgl@sss.pgh.pa.us>:
"Tomas Vondra" <tv@fuzzy.cz> writes:
> Dne 5 Listopad 2014, 18:10, Tom Lane napsal(a):
>> For some reason there's over 1000 times more rows in andalertsmatch in
>> the 9.1.14 installation.  I'm betting on a foulup somewhere in the data
>> dump/restore process.

> I'd bet that's mostly due to rescans in the merge join ...

Doh, I should have thought of that :-(.  But still, the difference in
the number of final output rows is pretty compelling evidence that
it's not really the same data.

                        regards, tom lane

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