Craig Ringer <craig@postnewspapers.com.au> wrote:
> Some of those tables are views composed of multiple unions, too,
> by the looks of things.
>
> Doesn't the planner have some ... issues ... with estimation of
> row counts on joins over unions? Or is my memory just more faulty
> than usual?
So far I can't tell if it's views with unions or (as I suspect)
inheritance. The views and tables shown so far reference other
objects not yet shown:
core.inventory
h.location
h.actor
However, I'm pretty sure that the problem is that the estimated row
count explodes for no reason that I can see when the "Nested Loop
Left Join" has an "Append" node from a parent table on the right.
28 rows joined to a 4 row append yields 51160 rows?
51160 rows joined to a 2 row append yields 203176856 rows?
203176856 rows joined to a 2 row append yields 806903677108 rows?
Something seems funny with the math. I would have expected 28 times
4 times 2 times 2, equaling 448. Still higher than 15, but only by
one order of magnitude -- where it might still make relatively sane
plan choices.
-Kevin
