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From: surya poondla <[email protected]>
To: songjinzhou <[email protected]>
Cc: dllggyx <[email protected]>
Cc: pgsql-bugs <[email protected]>
Subject: Re: BUG #19382: Server crash at __nss_database_lookup
Date: Fri, 20 Mar 2026 11:16:16 -0700
Message-ID: <CAOVWO5oH37CETZuxxXw3dhCMOHPMA0xFoJBWTpfJ06OV7sGzTQ@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
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	<[email protected]>

Hi Songjinzhou,

Thank you for reviewing the patch.

You're correct that there is a minor inefficiency, once a
tupDesc_identifier version mismatch is detected, the patch allocates
new_values/new_nulls arrays and calls deconstruct_expanded_record() before
knowing whether any field types actually differ.
If the version changed but no field types changed (e.g., a constraint-only
ALTER), we do unnecessary work and hit the if (!need_conversion) return
late.

That said, your suggestion is clean and correct. I can restructure the code
to do a first pass over the TupleDesc attributes (which is pure metadata,
no deconstruction needed) to set need_conversion,
and only proceed with deconstruct_expanded_record() and array allocation if
that returns true. This avoids any unnecessary memory allocation in that
intermediate case.

I'll post an updated patch with this improvement.

Thanks again for the careful review!

Regards,
Surya Poondla

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