Thank you, Tom, for this valuable information. On Tue, 01 Sep 2020 11:02:01 -0400 1Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > visibility rules are the same as for any other function. So the > answer to the OP's question depends on the transaction's isolation > level and (for typical PLs) on whether the function is VOLATILE or > not. > > serializable -> the transaction's initial snapshot is used throughout I suppose by writing serializable, you include repeatable read here, too? > > non serializable, volatile function -> each statement in the function > takes a fresh snapshot This is the needed behaviour for the validations I intend to do, then. > > non serializable, non-volatile function -> the function uses a single > snapshot. For a non-deferred trigger, I think it shares the snapshot > used by the triggering query. Not sure about exactly when the > snapshot is taken for a deferred trigger. So this case seems to be trickier than it looks at a first glance. It depends heavily on the use case, of course, in how far the snapshot time influences the correctness of a trigger written in this mode. I suggest adding this to the documentation and will try to use the commenting function there for it. Thanks! Dirk
