From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Julien Rouhaud <rjuju123(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Hypothetical indexes using BRIN broken since pg10 |
Date: | 2019-06-27 19:24:21 |
Message-ID: | 20190627192420.GA1028@alvherre.pgsql |
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Lists: | pgsql-hackers |
On 2019-Jun-27, Tom Lane wrote:
> Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> writes:
> > On 2019-Jun-27, Tom Lane wrote:
> >> FWIW, the proposed patch doesn't seem to me like it adds much more
> >> BRIN-specific knowledge to brincostestimate than is there already.
>
> > It's this calculation that threw me off:
> > statsData.revmapNumPages = (indexRanges / REVMAP_PAGE_MAXITEMS) + 1;
> > ISTM that selfuncs has no reason to learn about revmap low-level
> > details.
>
> Um ... it's accounting for revmap pages already (which is why it needs
> this field set), so hasn't that ship sailed?
Yes, but does it need to know how many items there are in a revmap page?
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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