On Thursday, November 16, 2023, Tom Lane <
tgl@sss.pgh.pa.us> wrote:
That line of argument also leads to the conclusion that it'd be
okay to expose info about the ordering of the CTE result to the
upper planner. This patch doesn't do that, and I'm not sufficiently
excited about the issue to go write some code. But if someone else
does, I think we shouldn't exclude doing it on the grounds of wanting
to preserve an optimization fence. The fence is sort of one-way
in this line of thinking: information can propagate up to the outer
planner level, but not down into the CTE plan.
This is indeed my understanding of what materialized means. Basically, the CTE is done first and in isolation; but any knowledge of its result shape can be used when referencing it.
David J.