Re: Optimising a two column OR check

From: Justin Pryzby <pryzby(at)telsasoft(dot)com>
To: Ivan Voras <ivoras(at)gmail(dot)com>
Cc: postgres performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Optimising a two column OR check
Date: 2019-10-12 14:43:36
Message-ID: 20191012144336.GA4475@telsasoft.com
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On Sat, Oct 12, 2019 at 04:39:56PM +0200, Ivan Voras wrote:
> With seqscan disabled, I get this plan on 9.6:
> Bitmap Heap Scan on friend (cost=8.42..19.01 rows=14 width=8)
...
> I expected to get an index-only scan in this situation, as that would be a
> very common query. Is there a way to actually make this sort of query
> resolvable with an index-only scan? Maybe a different table structure would
> help?

The v11 release notes have this relevant item:

https://www.postgresql.org/docs/11/release-11.html
|Allow bitmap scans to perform index-only scans when possible (Alexander Kuzmenkov)

Justin

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