Tom Lane wrote: > Surely they require a unique constraint --- else the behavior isn't > even well defined, is it?
They require that the merge condition does not match for more than one row, but since the merge condition can do just about anything, there is no guarantee that a unique constraint encompasses it. -- Peter Eisentraut http://developer.postgresql.org/~petere/ ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
