On Wed, Jun 02, 2004 at 09:52:28AM -0400, Tom Lane wrote: > 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.
Why would it overwrite cmin? Only a new xmin is needed (and cmax and xmax, but the cursors don't care about those) -- Alvaro Herrera (<alvherre[a]dcc.uchile.cl>) "La fuerza no está en los medios físicos sino que reside en una voluntad indomable" (Gandhi) ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
