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From: Ayush Tiwari <[email protected]>
To: [email protected]
To: [email protected]
Subject: Re: BUG #19468: Prevent SIGSEGV on FETCH after ALTER TYPE of cursor rowtype
Date: Mon, 27 Apr 2026 17:42:57 +0530
Message-ID: <CAJTYsWU6BxT5T_kqdAhnQncGGj0aCR-P1aKQdxexdd3aW_WdiA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

Hi,

On Mon, 27 Apr 2026 at 17:03, PG Bug reporting form <[email protected]>
wrote:

> The following bug has been logged on the website:
>
> Bug reference:      19468
> Logged by:          HaoGang Mao
> Email address:      [email protected]
> PostgreSQL version: 17.3
> Operating system:   OS: Linux (Docker)
> Description:
>
> Summary:
> PostgreSQL crashes with SIGSEGV when a cursor is open over a composite
> type and the type is modified via ALTER TYPE during the same transaction,
> followed by a second FETCH.
>
> Reproduction steps (minimal):
>   CREATE TYPE foo AS (a INT, b INT);
>   BEGIN;
>   DECLARE c CURSOR FOR
>     SELECT (i, power(2, 30))::foo
>     FROM generate_series(1,10) i;
>   FETCH c;
>   ALTER TYPE foo ALTER ATTRIBUTE b TYPE TEXT;
>   FETCH c;
>   COMMIT;
>
> Expected: Error message (type modified during active cursor)
> Actual:   Server process terminated with signal 11 (Segmentation fault)
>
> Confirmed environment:
>   PostgreSQL 18.3, built from source with --enable-cassert --enable-debug
>   Docker image: sqleek-pg18-debug:18.3
>   Reproduction / stack script: report/postgres/get_stack3.sh
>   Full stack output: report/postgres/crash_stack4.txt
>

Looks the same as [1].

Regards,
Ayush

[1] PostgreSQL: Re: BUG #19466: Server crash (SIGSEGV) when FETCH after
ALTER TYPE during open cursor
<https://www.postgresql.org/message-id/CAJTYsWUJRkCEopx07tSMX8MGcxzf0CJQh3di2XhetquzdiiVOQ%40mail.gma...;

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