Robert Haas <> writes:
> Yay!  I'm excited about this, particularly the possible "pipelining"
> stuff, where you can do WITH (DELETE .. RETURNING ..) INSERT ...  and
> have it be like cool and fast and stuff.

> Or at least I hope you can do that.

It's gonna need some work yet.  As things stand, the tuples are indeed
pipelined through, but the CteScan nodes *also* stash them aside into
tuplestores, just in case somebody demands a rescan.  Fixing that will
require revisiting the exec flags (EXEC_FLAG_REWIND etc).  We don't
currently distinguish "it's unlikely you'll have to rescan" from
"you're guaranteed not to have to rescan", but a CteScan that's covering
a ModifyTable has to know the latter to not have to keep hold of copies
of the RETURNING tuples.

It might be a small enough change to do after alpha starts, but I don't
have time for it right now.

                        regards, tom lane

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