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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.

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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.

  • I want to understand it, and I would also like to know if I can use something like pgstattuple to see the insertion status of large table creations (a billion rows) with CTAS. I do them pretty often for this site, just finished an answer with 100 million insertions in CTAS. – Evan Carroll Jun 2 '17 at 3:10

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