Re: Question Regarding Merge Append and Parallel Execution of Index Scans on Partitioned Table

From: Ayush Vatsa <ayushvatsa1810(at)gmail(dot)com>
To: David Rowley <dgrowleyml(at)gmail(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Question Regarding Merge Append and Parallel Execution of Index Scans on Partitioned Table
Date: 2025-06-05 19:48:52
Message-ID: CACX+KaNB0O4pJep0QukyR=c7GMxQTWjRGnJemm5OsCxRWRuJnw@mail.gmail.com
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> The input node to the Gather Merge needs to be sorted by
> something, and the output of the Gather Merge will be sorted by the
> same thing.
Ok now I got that. Thanks for the clarification.

Last small question:
As of now parallelism in merge append is not supported, but it could
be something we can consider implementing in the future.

That said, I’m wondering if this might not be necessary, given that
Gather Merge already accomplishes similar functionality. Would
love to hear your thoughts on whether there’s a distinct advantage to
adding parallelism to Merge Append or if Gather Merge sufficiently
covers all the use cases.

-----------------
Thanks,
Ayush Vatsa
SDE AWS

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