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From: Tom Lane <[email protected]>
To: Yura Sokolov <[email protected]>
Cc: David Rowley <[email protected]>
Cc: PostgreSQL Developers <[email protected]>
Subject: Re: Fix BUG #17335: Duplicate result rows in Gather node
Date: Tue, 25 Jan 2022 11:32:35 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
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Yura Sokolov <[email protected]> writes:
> В Вт, 25/01/2022 в 21:20 +1300, David Rowley пишет:
>> The reason I didn't think it was worth adding a new test was that no
>> tests were added in the original commit.  Existing tests did cover it,

> Existed tests didn't catched the issue. It is pitty fix is merged
> without test case it fixes.

I share David's skepticism about the value of a test case.  The
failure mode that seems likely to me is some other code path making
the same mistake, which a predetermined test would not catch.

Therefore, what I think could be useful is some very-late-stage
assertion check (probably in createplan.c) verifying that the
child of a Gather is parallel-aware.  Or maybe the condition
needs to be more general than that, but anyway the idea is for
the back end of the planner to verify that we didn't build a
silly plan.

			regards, tom lane

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