Thanks Tom, that made it clear I made a mistake.
> That's the way it's supposed to be --- the scantuple slot is for > scanning your subplan's output. Browsing through the code I get the impression, that - ecxt_scantuple is only used by Scan nodes (i.e. SeqScan, IndexScan, SubqueryScan and FunctionScan) - ecxt_innertuple and ecxt_outertuple are used by Join nodes (but they don't use the ecxt_scantuple at all). Is it right that the ecxt_scantuple is only used by leafnodes (Scans) and never by Joins? > > I have written a new executor node Foo, with corresponding ExecFoo and > make_foo functions. I have also written a new Expr type called Bar, along > with a ExecEvalBar. > > > In make_foo I append some Bar columns. When I try to evaluate the Bar > columns in ExecFoo via ExecProject, I need the Bar columns to access each > other. > > That makes no sense at all. ExecProject can't be expected to access > output columns of the current node --- they haven't been computed yet. Conceptionally my only way is then to crack the dependency between the Bar columns by splitting the computation in different nodes - and then put these nodes atop of each other. But then, I still don't get the relationship between INNER, OUTER varnos on the one side and ecxt_scantuple, ecxt_outertuple and ecxt_innertuple on the other side. May a non-leaf node refer to a Var with a 'normal' scan varno or only to INNER and OUTER varnos? How is my Foo node supposed to access the suplan's (whatever that might me, a Scan or a Join) columns? Should Foo'- tlist have Vars with OUTER varnos and the right varattos? I cannot find an example of a node that (1) does projection and (2) is not a Scan (i.e a leaf node) and (3) uses ecxt_scantuple to pipe information to an upper node. I'd be happy if you clarified my misconceptions, I greatly appreciate your help. Regards Peter ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
