You'd not have to take an ACCESS EXCLUSIVE. A lower level would suffice, e.g. SHARE UPDATE EXCLUSIVE, which still allows data changes.
> There is nobody else doing DDLs except me - Mr. DBA, so I guess I am > safe on this side. ;)
If autovacuum triggered a vacuum/analyze it'd would e.g. also try to update pg_class.
I can so to say then use the strategy behind Peter Eisentraut's patch (reduce index rename locks) applied in version 12 in my case (9.3) manually.
As far as I can see (and understand the source code), only the table holding the index is locked (and not pg_class).
db=# begin; BEGIN db=*# lock table x in share update exclusive mode; LOCK TABLE db=*# update pg_class set relname = 'y_idx' where oid = 'x_idx'::regclass; UPDATE 1 db=*# commit; COMMIT
It looks good. The only exceptional case I am able to discover is when the index is used within a constraint, in which case I should also update pg_constraint.