Re: BUG #19469: Prevent SIGSEGV on FETCH after ALTER TYPE of cursor rowtype

On 27/04/26 07:53, PG Bug reporting form wrote:
> The following bug has been logged on the website:
>
> Bug reference: 19469
> Logged by: HaoGang Mao
> Email address: haogangmao(at)gmail(dot)com
> PostgreSQL version: 17.3
> Operating system: OS: Linux (Docker)
> Description:
>
> An open cursor can continue returning tuples built with the old physical
> layout of a named composite type. If that type is changed in the same
> transaction (for example ALTER TYPE ... ALTER ATTRIBUTE ... TYPE), a later
> FETCH may format the tuple using updated descriptor and output metadata.
>
> Minimal Reproduction SQL:
> ```sql
> 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;
> ```

It looks the same as as [1] and [2]

[1]
https://www.postgresql.org/message-id/19466-dc32827173299fd4%40postgresql.org
[2]
https://www.postgresql.org/message-id/19382-4c2060ffee72759b%40postgresql.org

--
Matheus Alcantara
EDB: https://www.enterprisedb.com