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Explain dropdb can't use syscache because of TOAST

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Add a comment explaining dropdb() can't rely on syscache. The issue with
flattened rows was fixed by commit 0f92b230f88b, but better to have
a clear explanation why the systable scan is necessary. The other places
doing in-place updates on pg_database have the same comment.

Suggestion and patch by Yugo Nagata. Backpatch to 12, same as the fix.

Author: Yugo Nagata
Backpatch-through: 12
Discussion: https://postgr.es/m/CAJTYsWWNkCt+-UnMhg=BiCD3Mh8c2JdHLofPxsW3m2dkDFw8RA@mail.gmail.com
This commit is contained in:
Tomas Vondra 2024-08-19 13:31:51 +02:00
parent 23c200940e
commit e498d22e21
1 changed files with 3 additions and 1 deletions
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4
src/backend/commands/dbcommands.c
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@ -1663,7 +1663,9 @@ dropdb(const char *dbname, bool missing_ok, bool force)
pgstat_drop_database(db_id); pgstat_drop_database(db_id);
/* /*
* Update the database's pg_database tuple * Get the pg_database tuple to scribble on. Note that this does not
* directly rely on the syscache to avoid issues with flattened toast
* values for the in-place update.
*/ */
ScanKeyInit(&scankey, ScanKeyInit(&scankey,
Anum_pg_database_datname, Anum_pg_database_datname,