Bruce Momjian <[EMAIL PROTECTED]> writes: > Tom Lane wrote: >> This is exactly the same argument as not being able to overwrite cmin.
> Basically the phantom xid's are a shorthand for saying the tuple was > created by xid1 and deleted by xid2, both part of the same main > transaction. > A cursor looking at the rows has to recognize the xid is a phantom (via > pg_subtrans) and look up the creation xid. You still don't see the point. Consider BEGIN; DECLARE CURSOR c1 FOR SELECT * FROM a ...; INSERT INTO a VALUES(...); -- call this row x DECLARE CURSOR c2 FOR SELECT * FROM a ...; BEGIN; DELETE FROM a WHERE ...; -- assume this deletes row x ROLLBACK; FETCH FROM c1; -- must NOT see row x FETCH FROM c2; -- must see row x AFAICS your proposal does not support this. The two cursors' snapshots will differ only in the recorded current-cid for the outer transaction. If the subtrans has overwritten xmin/cmin, there is no way to make that decision correctly. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 8: explain analyze is your friend