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From: legrand legrand <legrand_legrand@hotmail.com>
To: pgsql-performance@postgresql.org
Subject: Re: Many DataFileRead - IO waits
Date: Fri, 28 Feb 2020 12:00:09 -0700 (MST)
Message-ID: <1582916409615-0.post@n3.nabble.com> (raw)
In-Reply-To: <CAEPE5bMHZ3vLS85O7dTFGhRg+SG=Z2=dDbupAmjNAnDEBPayYQ@mail.gmail.com>
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	<CAEPE5bMHZ3vLS85O7dTFGhRg+SG=Z2=dDbupAmjNAnDEBPayYQ@mail.gmail.com>

Hello,
I'm not able to use your perfs diagrams, 
but it seems to me that not using 3rd column of that index (int_otherid2)
generates an IO problem.

Could you give us the result of

explain (analyze,buffers) SELECT
tabledata.uuid_id,tabledata.int_id,tabledata.timestamp_date,tabledata.int_otherid,tabledata.float_value,tabledata.int_otherid2,tabledata.int_otherid3,tabledata.int_rowver
FROM tabledata 
WHERE timestamp_date <= '2020-02-24 03:05:00.013'::timestamp without time
zone
ND int_otherid3 = '3ad2b707-a068-42e8-b0f2-6c8570953760'
AND tabledata.int_id=8149 
ORDER BY timestamp_date DESC 
LIMIT 1

and this for each value of int_otherid3 ?
and tell us if you are able to change the sql ?

Thanks
Regards
PAscal



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