From: Jesper Pedersen <jesper.pedersen@redhat.com>
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org, Thomas Munro <munro@ip9.org>
Subject: Re: Index Skip Scan
Date: Tue, 9 Oct 2018 09:58:09 -0400
Message-ID: <b0949c46-ec77-4b82-48fe-916cd5c12fd1@redhat.com> (raw)
In-Reply-To: <153909254478.1479.11809244127214809171.pgcf@coridan.postgresql.org>
References: <707b6f68-16fa-7aa7-96e5-eeb4865e6a30@redhat.com>
<CA+q6zcXdP=PCaVRx3OgpyKK+NgNfrnnSA66rkvxRLeZrkYjEaA@mail.gmail.com>
<153909254478.1479.11809244127214809171.pgcf@coridan.postgresql.org>
Hi Pavel,
On 10/9/18 9:42 AM, Pavel Stehule wrote:
> I tested last patch and I have some notes:
>
> 1.
>
> postgres=# explain select distinct a10000 from foo;
> +-------------------------------------------------------------------------------------------+
> | QUERY PLAN |
> +-------------------------------------------------------------------------------------------+
> | Unique (cost=0.43..4367.56 rows=9983 width=4) |
> | -> Index Skip Scan using foo_a10000_idx on foo (cost=0.43..4342.60 rows=9983 width=4) |
> +-------------------------------------------------------------------------------------------+
> (2 rows)
>
> In this case Unique node is useless and can be removed
>
> 2. Can be nice COUNT(DISTINCT support) similarly like MIN, MAX suppport
>
> 3. Once time patched postgres crashed, but I am not able to reproduce it.
>
Please, send that query through if you can replicate it. The patch
currently passes an assert'ed check-world, so your query clearly
triggered something that isn't covered yet.
> Looks like very interesting patch, and important for some BI platforms
>
Thanks for your review !
Best regards,
Jesper
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To: pgsql-hackers@postgresql.org
Cc: jesper.pedersen@redhat.com, pavel.stehule@gmail.com, munro@ip9.org
Subject: Re: Index Skip Scan
In-Reply-To: <b0949c46-ec77-4b82-48fe-916cd5c12fd1@redhat.com>
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