| From: | Alvaro Herrera <alvherre(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | BRIN cost estimate |
| Date: | 2015-11-16 13:52:39 |
| Message-ID: | 20151116135239.GV614468@alvherre.pgsql |
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| Lists: | pgsql-hackers |
Somebody wrote to me a few days ago that the BRIN cost estimation is
rather poor. One immediately obvious issue which I think is easily
fixed is the correlation estimate, which is currently hardcoded to 1.
Since a BRIN scan always entails a scan of the relation in physical
order, it's simple to produce a better estimate for that, per the
attached patch. (Note: trying to run this on expression indexes will
cause a crash. I need to complete that part ...)
There are other improvements we've been discussing, but I'm unclear that
I will have time to study them to get a useful patch quickly enough. If
somebody else wants to mess with this, please get in touch.
Thoughts?
--
Álvaro Herrera 33.5S 70.5W
| Attachment | Content-Type | Size |
|---|---|---|
| brin-correlation.patch | text/x-diff | 3.2 KB |
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