pg.ddx.io pgsql-hackers@postgresql.org mailing list archive help / color / mirror / Atom feed From: Floris Van Nee <florisvannee@Optiver.com>
To: Dmitry Dolgov <9erthalion6@gmail.com>
To: David Rowley <david.rowley@2ndquadrant.com>
To: Jesper Pedersen <jesper.pedersen@redhat.com>
Cc: Thomas Munro <thomas.munro@gmail.com>
Cc: James Coleman <jtc331@gmail.com>
Cc: Rafia Sabih <rafia.pghackers@gmail.com>
Cc: Jeff Janes <jeff.janes@gmail.com>
Cc: Peter Geoghegan <pg@bowt.ie>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>
Cc: Bhushan Uparkar <bhushan.uparkar@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Cc: Alexander Korotkov <a.korotkov@postgrespro.ru>
Subject: Re: Index Skip Scan
Date: Wed, 10 Jul 2019 14:52:21 +0000
Message-ID: <1562770342222.94509@Optiver.com> (raw )
In-Reply-To: <CA+q6zcU66Gx954SjOT5nZRRbYG-gVVNJx5NSbn3Gn2aKwtaX1Q@mail.gmail.com >
References: <2685f020-f302-9bf6-1b5c-ebc2bcebc635@2ndquadrant.com >
<CA+q6zcXcSftAxfwuK5c186E8ckZeWmOO07GFvpoOx-wpsDGGzA@mail.gmail.com >
<CA+q6zcVn10QzbSh686PaZpxgxMhxABRj7aJJpsJ=tKkmcSrBew@mail.gmail.com >
<CA+q6zcUVAnfSOaSk3s9Sbj6yC7LrDYChSyJd0t7u6Q=97k5a=A@mail.gmail.com >
<CA+q6zcVQG0ufA_5m_7eeHLN2VRy+z8Kf9FoZ2NnF=yd0_43ndg@mail.gmail.com >
<CA+q6zcXxwU1FZ=Tj0kWeTkrJ1N9=fhrUH1t5N_yHEcKsG=+qUw@mail.gmail.com >
<1559361698401.22864@Optiver.com >
<1559362223126.18661@Optiver.com >
<CA+FpmFeKh9BAhDTAf-ZWQ=pvVaRy+Lnahb_8=OOFqcVXJDBWWQ@mail.gmail.com >
<988b7763-5c55-1be1-b7b6-f3a68eff0d40@redhat.com >
<CA+q6zcVnRRqktw4cg2Vddy3S+VY3Tsmit0kausYtctvsTum7tA@mail.gmail.com >
<1559763453006.85615@Optiver.com >
<1559763570329.85227@Optiver.com >
<4d469bf2-49ff-bc3d-a428-6c7b5d87d526@redhat.com >
<CAKJS1f86FgODuUnHiQ25RKeuES4qTqeNxm1QbqJWrBoZxVGLiQ@mail.gmail.com >
<CA+q6zcXoYjCtyU-jFU_=p2DL_K3BHbBEEbJHaJTxdvRX3cU-Sg@mail.gmail.com >
<CA+q6zcVVigO_1KRBxvzKfnR593CEE7FKR-bwP-XcH6AVHOo4+g@mail.gmail.com >
<a8b5c2d9-7b23-e12b-fc6b-eee63dc8dacf@redhat.com >
<CA+hUKGKo30N5VNuRWhDuMGVZ3hTcv4J5RGXe286GRJZLk_jBYQ@mail.gmail.com >
<CAKJS1f_v5X1Sb42ShOhsLzuMA6iX52PcBwpf4P-L9H_GDYA3-Q@mail.gmail.com >
<CA+hUKG+oY0u1YON4KHikmX0aO6tFBOF_LzZQOTX8bVUbe1j5mA@mail.gmail.com >
<CA+q6zcWC2BgJwFf31xQUZ+FbP+J0zR8fM0sGVMuCYJDbAW_GAw@mail.gmail.com >
<1562769595280.16860@Optiver.com >
<CA+q6zcU66Gx954SjOT5nZRRbYG-gVVNJx5NSbn3Gn2aKwtaX1Q@mail.gmail.com >
> Thanks for testing! Could you provide a test case to show what exactly is the
> problem?
create table a (a int, b int, c int);
insert into a (select vs, ks, 10 from generate_series(1,5) vs, generate_series(1, 10000) ks);
create index on a (a,b);
analyze a;
set enable_indexskipscan=1; // setting this to 0 yields different results
set random_page_cost=1;
explain SELECT DISTINCT ON (a) a,b FROM a;
BEGIN;
DECLARE c SCROLL CURSOR FOR SELECT DISTINCT ON (a) a,b FROM a;
FETCH FROM c;
FETCH BACKWARD FROM c;
FETCH 6 FROM c;
FETCH BACKWARD 6 FROM c;
FETCH 6 FROM c;
FETCH BACKWARD 6 FROM c;
END;
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To: pgsql-hackers@postgresql.org
Cc: florisvannee@Optiver.com, 9erthalion6@gmail.com, david.rowley@2ndquadrant.com, jesper.pedersen@redhat.com, thomas.munro@gmail.com, jtc331@gmail.com, rafia.pghackers@gmail.com, jeff.janes@gmail.com, pg@bowt.ie, tomas.vondra@2ndquadrant.com, thomas.munro@enterprisedb.com, bhushan.uparkar@gmail.com, a.korotkov@postgrespro.ru
Subject: Re: Index Skip Scan
In-Reply-To: <1562770342222.94509@Optiver.com>
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