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Re: Improve hash join's handling of tuples with null join keys - Mailing list pgsql-hackers

From Marc-Olaf Jaschke
Subject Re: Improve hash join's handling of tuples with null join keys
Date
Msg-id 96AC93D7-9A4E-43EE-9CD9-23E973FE8D40@dshare.de
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In response to Re: Improve hash join's handling of tuples with null join keys  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Improve hash join's handling of tuples with null join keys
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Tom Lane wrote:

> Bug #19030 [1] seems to be a fresh report of the problem this patch
> aims to solve.

> [1] https://www.postgresql.org/message-id/flat/19030-944dd78d7ef94c0f%40postgresql.org
>

I can confirm that the patch fixes the issue (Bug #19030). The memory usage remains within the expected range of
work_mem.
This also applies to parallel hash joins.
The query also runs significantly faster.
I also tested cases with multiple left joins.
I have only observed this problem when there are many null values in the join column.

regards
Marc-Olaf Jaschke

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