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Re: SELECT DISTINCT chooses parallel seqscan instead of indexscan on huge table with 1000 partitions - Mailing list pgsql-general

From Dimitrios Apostolou
Subject Re: SELECT DISTINCT chooses parallel seqscan instead of indexscan on huge table with 1000 partitions
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Msg-id 2e3947bd-b01c-37c8-00e1-d8e925e79597@gmx.net
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In response to Re: SELECT DISTINCT chooses parallel seqscan instead of indexscan on huge table with 1000 partitions  (David Rowley <dgrowleyml@gmail.com>)
Responses Re: SELECT DISTINCT chooses parallel seqscan instead of indexscan on huge table with 1000 partitions
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On Sat, 11 May 2024, David Rowley wrote:

> On Sat, 11 May 2024 at 13:33, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> I do kind of wonder why it's producing both a hashagg and a Unique
>> step --- seems like it should do one or the other.
>
> It still needs to make the duplicate groups from parallel workers unique.

Range partitioning of the table guarantees that, since the ranges are not
overlapping.


Dimitris

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