Re: Why could different data in a table be processed with differentperformance? - Mailing list pgsql-performance

From Justin Pryzby
Subject Re: Why could different data in a table be processed with differentperformance?
Date
Msg-id 20180925021954.GW2471@telsasoft.com
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In response to Re: Why could different data in a table be processed with different performance?  (Vladimir Ryabtsev <greatvovan@gmail.com>)
Responses Re: Why could different data in a table be processed with different performance?  (Vladimir Ryabtsev <greatvovan@gmail.com>)
List pgsql-performance
On Mon, Sep 24, 2018 at 05:59:12PM -0700, Vladimir Ryabtsev wrote:
> > I *suspect* VACUUM FULL won't help, since (AIUI) it copies all "visible"
...
> I am going copy the slow range into a table nearby and see if it reproduces
> (I hope "INSERT INTO t2 SELECT * FROM t1 WHERE ..." will keep existing
> order of rows). Then I could try the same after CLUSTER.

If it does an index scan, I think that will badly fail to keep the same order
of heap TIDs - it'll be inserting rows in ID order rather than in (I guess)
reverse ID order.

Justin


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