| From: | Alexander Kuzmenkov <a(dot)kuzmenkov(at)postgrespro(dot)ru> |
|---|---|
| To: | jesper(dot)pedersen(at)redhat(dot)com |
| Cc: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, pg(at)bowt(dot)ie, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, bhushan(dot)uparkar(at)gmail(dot)com, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
| Subject: | Re: Index Skip Scan |
| Date: | 2018-09-13 19:36:24 |
| Message-ID: | 3cfd317e-2a8b-8681-0833-8f2ead3af4d4@postgrespro.ru |
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| Lists: | pgsql-hackers |
El 13/09/18 a las 18:39, Jesper Pedersen escribió:
>
> Yes, this doesn't look good. Using your test case I'm seeing that
> unique is being chosen when the group size is below 34, and skip
> above. This is with the standard initdb configuration; did you change
> something else ? Or did you force the default plan ?
Sorry I didn't mention this, the first column is indeed forced skip
scan, just to see how it compares to index scan.
> This is something to look at -- maybe there is a way to use
> btpo_next/btpo_prev instead/too in order to speed things up. Atm we
> just have the scan key in BTScanOpaqueData. I'll take a look after my
> upcoming vacation; feel free to contribute those changes in the
> meantime of course.
>
I probably won't be able to contribute the changes, but I'll try to
review them.
--
Alexander Kuzmenkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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