Alvaro Herrera <alvherre@dcc.uchile.cl> writes:
> Not sure how to fix this -- I'm not even sure what the exact problem is,
> because it's trying to insert the oid of a toast table in
> pg_class_oid_index during the first ALTER TABLE ... CREATE TOAST TABLE.
> Why would it see an old tuple with the same value, I don't know.
This is probably an UPDATE operation not an INSERT. There are quite a
few paths through CREATE TABLE that involve repeated updates of the
new pg_class row.
I would think however that these changes would occur as successive
commands of a single transaction, not as subtransactions, unless you've
done something odd to CommandCounterIncrement.
regards, tom lane