When does a table get an oid?

Question

I'm wondering when a table acquires an oid. Is it only when the transaction commits? Or does it have a hidden oid prior to commit? Especially in the context of a CREATE TABLE AS SELECT.

Answer 1

Table OIDs are assigned quite early in table creation, and are definitely present by the time the CREATE TABLE finishes (before xact commit), since the row is visible in pg_class by then.

The new pg_class row (and its oid) are not visible to concurrent transactions until commit, though.

It's not clear why you care, though. It shouldn't matter.