On Friday, June 19, 2020, Laurenz Albe <laurenz.a...@cybertec.at> wrote:
> > > I am absolutely aware that those are hashed sub plans below a seqscan > and that Postgres therefore has to scan all tuples of the table. But the > problem is that upper nodes (which are excluded from > > this example for simplicity) think they will receive 1301316 rows from > the seqscan, when in fact they will probably only see a hand full, which > the planner could have (easily?) deduced by taking the > > greater of the two subplan row estimates. > > > > What am I missing, or is this perhaps a shortfall of the planner? > > The subplans are executed *fpr each row* found in "transactions", > and the estimate on the subplans is *per execution". > I understood Tom’s nearby answer but not this one. This seems to be referring to correlated subplans which the examples are not. David J.
