| From: | Sergey Shinderuk <s(dot)shinderuk(at)postgrespro(dot)ru> |
|---|---|
| To: | Richard Guo <guofenglinux(at)gmail(dot)com> |
| Cc: | David Rowley <dgrowleyml(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, David Rowley <drowley(at)postgresql(dot)org> |
| Subject: | Re: Bug in row_number() optimization |
| Date: | 2022-12-01 11:21:47 |
| Message-ID: | c039da79-d434-fa21-5de6-f0a0a7257a61@postgrespro.ru |
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| Lists: | pgsql-hackers |
On 01.12.2022 11:18, Richard Guo wrote:
>
> On Mon, Nov 28, 2022 at 5:59 PM Sergey Shinderuk
> <s(dot)shinderuk(at)postgrespro(dot)ru <mailto:s(dot)shinderuk(at)postgrespro(dot)ru>> wrote:
>
> Not quite sure that we don't need to do anything for the
> WINDOWAGG_PASSTHROUGH_STRICT case. Although, we won't return any more
> tuples for the current partition, we still call ExecProject with
> dangling pointers. Is it okay?
>
> AFAIU once we go into WINDOWAGG_PASSTHROUGH_STRICT we will spool all the
> remaining tuples in the current partition without storing them and then
> move to the next partition if available and become WINDOWAGG_RUN again
> or become WINDOWAGG_DONE if there are no further partitions. It seems
> we would not have chance to see the dangling pointers.
Maybe I'm missing something, but the previous call to spool_tuples()
might have read extra tuples (if the tuplestore spilled to disk), and
after switching to WINDOWAGG_PASSTHROUGH_STRICT mode we nevertheless
would loop through these extra tuples and call ExecProject if only to
increment winstate->currentpos.
--
Sergey Shinderuk https://postgrespro.com/
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