Re: 'WARNING: you don't own a lock of type ExclusiveLock' is printed during the GRANT command on PostgreSQL16.5

On Tue, Nov 19, 2024 at 10:27:42PM -0800, Noah Misch wrote:
> On Wed, Nov 20, 2024 at 05:11:07AM +0000, Aya Iwata (Fujitsu) wrote:
> > During our tests on November release,
> > we discovered a "WARNING: you don't own a lock of type ExclusiveLock" that occurred at a strange time in GRANT command.

> > This is only possible when psql executes each command individually.
> > $ psql -d postgres -c "CREATE USER nmluser1;"
> > CREATE ROLE
> > $ psql -d postgres -c "CREATE TABLESPACE test_tblspace LOCATION '/xxx /xxx/pgsql16.5/tbs';"
> > CREATE TABLESPACE
> > $ psql -d postgres -c "CREATE DATABASE enc_testdb;"
> > CREATE DATABASE
> > $ psql -d postgres -c "GRANT ALL PRIVILEGES ON DATABASE postgres TO nmluser1;"
> > GRANT
> > $ psql -d postgres -c "GRANT ALL PRIVILEGES ON DATABASE enc_testdb TO nmluser1;"
> > GRANT
> > $ psql -d postgres -c "GRANT CREATE ON TABLESPACE test_tblspace TO nmluser1;"
> > WARNING:  you don't own a lock of type ExclusiveLock
> > GRANT

Did you ever see the WARNING with a DATABASE command, or just with a
TABLESPACE command?

> Thanks for the report. This seems reasonably likely to come from a defect in
> commit 51ff46d. I will look into it.

Yes, that commit had us reading cc_relisshared before that field got
initialized. I can reproduce the WARNING in v16+, with GRANT TABLESPACE.
Before a cache's initialization cc_relisshared==false, so
SearchSysCacheLocked1() used the wrong locktag. The attached patch is about
right. At a minimum, I still need to work on the details in its log message.