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help / color / mirror / Atom feedFrom: Michael Paquier <[email protected]>
To: Chao Li <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Cc: Michael Paquier <[email protected]>
Cc: Corey Huinker <[email protected]>
Subject: Re: Fix small issues of pg_restore_extended_stats()
Date: Mon, 18 May 2026 13:19:02 +0900
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
On Mon, May 18, 2026 at 10:25:16AM +0800, Chao Li wrote:
> 1. Inconsistent expression key verification behavior
>
> This function is actually doing a prefix comparison using the input
> key length, so as long as an input key matches a prefix of a valid
> key name, the function returns true.
>
> At runtime, it does not lead to an incorrect value being imported,
> because the invalid key will still be filtered out later. But one
> bad scenario I can imagine is that a user is trying to set
> “correlation”, and accidentally omits the last “n”. In that case,
> the key is silently discarded and the user is not aware of it, which
> can lead to a surprising result.
It's a silent data loss, with data getting ignored. The call should
report a failure because the key does not match with a name we'd
expect. pg_dump would not generate that, but stats injection is a
supported use-case so that would be confusing.
Nice investigation.
> 2. Wrong number in a warning message
>
> The warning message says “3 required”, but it should be “1
> required”.
Harmless, still wrong.
> 3. Inconsistent heap_freetuple()
>
> In pg_clear_extended_stats(), heap_freetuple(tup) is only called
> before the final return. However, in two earlier paths, the function
> only emits warning messages and returns. It seems those paths should
> also call heap_freetuple(tup).
In the !IsValid() case, there is nothing to free, but you are right
about the second case where stxrelid does not match. It's minor, but
I don't have an argument against doing that either, and the free at
the bottom is a trace that we want to be consistent.
I'll go fix all that. Thanks for the report!
--
Michael
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Subject: Re: Fix small issues of pg_restore_extended_stats()
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