Re: Asymmetric partition-wise JOIN

From: "Andrey V(dot) Lepikhov" <a(dot)lepikhov(at)postgrespro(dot)ru>
To: Jaime Casanova <jcasanov(at)systemguards(dot)com(dot)ec>, Aleksander Alekseev <afiskon(at)gmail(dot)com>
Cc: pgsql-hackers(at)lists(dot)postgresql(dot)org, KaiGai Kohei <kaigai(at)heterodb(dot)com>
Subject: Re: Asymmetric partition-wise JOIN
Date: 2021-09-14 06:37:39
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On 9/9/21 8:38 PM, Jaime Casanova wrote:
> On Thu, Sep 09, 2021 at 09:50:46AM +0000, Aleksander Alekseev wrote:
>> It looks like this patch needs to be updated. According to it applies but doesn't pass any tests. Changing the status to save time for reviewers.
>> The new status of this patch is: Waiting on Author
> Just to give some more info to work on I found this patch made postgres
> crash with a segmentation fault.
> """
> Program terminated with signal SIGSEGV, Segmentation fault.
> #0 0x0000556e37ef1b55 in bms_equal (a=0x7f6e37a9c5b0, b=0x7f6e37a9c5b0) at bitmapset.c:126
> 126 if (shorter->words[i] != longer->words[i])
> """
> attached are the query that triggers the crash and the backtrace.

Thank you for this good catch!
The problem was in the adjust_child_relids_multilevel routine. The
tmp_result variable sometimes points to original required_outer.
This patch adds new ways which optimizer can generate plans. One
possible way is optimizer reparameterizes an inner by a plain relation
from the outer (maybe as a result of join of the plain relation and
partitioned relation). In this case we have to compare tmp_result with
original pointer to realize, it was changed or not.
The patch in attachment fixes this problem. Additional regression test

Andrey Lepikhov
Postgres Professional

Attachment Content-Type Size
v18-0001-Asymmetric-partitionwise-join.patch text/x-patch 39.7 KB

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