postgres.git / summary / log / commit / refs

commit    b3bb1e24b62c664dae694bfae6b409ac2b0aad3d
Author:   Tomas Vondra <tomas.vondra@postgresql.org>
Date:     Sun Aug 18 22:04:41 2024 +0000

    Fix DROP DATABASE for databases with many ACLs
    
    Commit c66a7d75e652 modified DROP DATABASE so that if interrupted, the
    database is known to be in an invalid state and can only be dropped.
    This is done by setting a flag using an in-place update, so that it's
    not lost in case of rollback.
    
    For databases with many ACLs, this may however fail like this:
    
      ERROR:  wrong tuple length
    
    This happens because with many ACLs, the pg_database.datacl attribute
    gets TOASTed. The dropdb() code reads the tuple from the syscache, which
    means it's detoasted. But the in-place update expects the tuple length
    to match the on-disk tuple.
    
    Fixed by reading the tuple from the catalog directly, not from syscache.
    
    Report and fix by Ayush Tiwari. Backpatch to 12. The DROP DATABASE fix
    was backpatched to 11, but 11 is EOL at this point.
    
    Reported-by: Ayush Tiwari
    Author: Ayush Tiwari
    Reviewed-by: Tomas Vondra
    Backpatch-through: 12
    Discussion: https://postgr.es/m/CAJTYsWWNkCt+-UnMhg=BiCD3Mh8c2JdHLofPxsW3m2dkDFw8RA@mail.gmail.com


 src/backend/commands/dbcommands.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c
index 974c5777bc3..7302e872939 100644
--- a/src/backend/commands/dbcommands.c
+++ b/src/backend/commands/dbcommands.c
@@ -827,6 +827,8 @@ dropdb(const char *dbname, bool missing_ok, bool force)
 	bool		db_istemplate;
 	Relation	pgdbrel;
 	HeapTuple	tup;
+	ScanKeyData scankey;
+	SysScanDesc scan;
 	Form_pg_database datform;
 	int			notherbackends;
 	int			npreparedxacts;
@@ -959,7 +961,18 @@ dropdb(const char *dbname, bool missing_ok, bool force)
 	 */
 	dropDatabaseDependencies(db_id);
 
-	tup = SearchSysCacheCopy1(DATABASEOID, ObjectIdGetDatum(db_id));
+	/*
+	 * Update the database's pg_database tuple
+	 */
+	ScanKeyInit(&scankey,
+				Anum_pg_database_datname,
+				BTEqualStrategyNumber, F_NAMEEQ,
+				CStringGetDatum(dbname));
+
+	scan = systable_beginscan(pgdbrel, DatabaseNameIndexId, true,
+							  NULL, 1, &scankey);
+
+	tup = systable_getnext(scan);
 	if (!HeapTupleIsValid(tup))
 		elog(ERROR, "cache lookup failed for database %u", db_id);
 	datform = (Form_pg_database) GETSTRUCT(tup);
@@ -985,6 +998,8 @@ dropdb(const char *dbname, bool missing_ok, bool force)
 	 */
 	CatalogTupleDelete(pgdbrel, &tup->t_self);
 
+	systable_endscan(scan);
+
 	/*
 	 * Drop db-specific replication slots.
 	 */


[parent: 45c3bd1131c5]