Hi hackers,
We encountered an issue lately, that if the database grants too many roles `datacl` is toasted, following which, the drop database command will fail with error "wrong tuple length".
To reproduce the issue, please follow below steps:
CREATE DATABASE test;
-- create helper function
CREATE OR REPLACE FUNCTION data_tuple() returns text as $body$
declare
mycounter int;
begin
for mycounter in select i from generate_series(1,2000) i loop
execute 'CREATE ROLE aaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbb ' || mycounter;
execute 'GRANT ALL ON DATABASE test to aaaaaaaaaaaaaaaaaaaaaaaaaaabbbbbbbbbbbbbbbbbbbbbb ' || mycounter;
end loop;
return 'ok';
end;
$body$ language plpgsql volatile strict;
-- create roles and grant on the database.
SELECT data_tuple();
-- drop database command, this will result in "wrong tuple length" error.
DROP DATABASE test;
The root cause of this behaviour is that the HeapTuple in dropdb function fetches a copy of pg_database tuple from system cache.
But the system cache flattens any toast attributes, which cause the length check to fail in heap_inplace_update.
A patch for this issue is attached to the mail, the solution is to change the logic to fetch the tuple by directly scanning pg_database rather than using the catcache.
Regards,
Ayush
