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From: Dimitrios Apostolou <[email protected]>
To: David Rowley <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: [email protected]
Subject: Re: SELECT DISTINCT chooses parallel seqscan instead of indexscan on huge table with 1000 partitions
Date: Mon, 13 May 2024 14:27:57 +0200 (CEST)
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAApHDvqWfGdUpTUp9s7AZYSeh44aLEXoBQS7UcfKM0zKhTCkiQ@mail.gmail.com>
References: <[email protected]>
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On Sat, 11 May 2024, David Rowley wrote:

> On Sat, 11 May 2024 at 13:33, Tom Lane <[email protected]> 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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