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help / color / mirror / Atom feedFrom: Richard Guo <[email protected]>
To: David Rowley <[email protected]>
Cc: Daniel Farkaš <[email protected]>
Cc: Magnus Hagander <[email protected]>
Cc: PostgreSQL mailing lists <[email protected]>
Subject: Re: BUG #17502: View based on window functions returns wrong results when queried
Date: Mon, 30 May 2022 17:18:44 +0800
Message-ID: <CAMbWs48yS=f8tj6zstiMd6yfV3U4YpssyB55PXqjcLUyUA5bww@mail.gmail.com> (raw)
In-Reply-To: <CAApHDvqKO00nNQtchBs65VTfjEMUsYiB5r2P4VUreTdXE9RY1g@mail.gmail.com>
References: <[email protected]>
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On Mon, May 30, 2022 at 9:12 AM David Rowley <[email protected]> wrote:
> The following is also pretty strange. Why should adding the SRF column
> to the ORDER BY change the number of output rows?
>
> postgres=# select distinct on (a) a,b, generate_Series(1,2) from ab
> order by a,b,3 desc;
> a | b | generate_series
> ---+---+-----------------
> 1 | 1 | 2
> 2 | 1 | 2
> (2 rows)
>
>
> postgres=# select distinct on (a) a,b, generate_Series(1,2) from ab
> order by a,b;
> a | b | generate_series
> ---+---+-----------------
> 1 | 1 | 1
> 1 | 1 | 2
> 2 | 1 | 1
> 2 | 1 | 2
> (4 rows)
>
This is indeed weird. This seems depends on at which plan level we add
ProjectSetPath. For the first query we insert ProjectSetPath at the
scan/join level, because the SRF is included in the ORDER BY, which
makes the SRF appear in the scan/join target. For the second query the
SRF is postponed to after the Sort.
Is this a bug we should fix?
Thanks
Richard
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To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: BUG #17502: View based on window functions returns wrong results when queried
In-Reply-To: <CAMbWs48yS=f8tj6zstiMd6yfV3U4YpssyB55PXqjcLUyUA5bww@mail.gmail.com>
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