Re: Searching for the cause of a bad plan

Csaba Nagy <nagy@ecircle-ag.com> writes:
> Looking at Plan 2, it looks like the "limit" step is estimating wrongly
> it's cost.

The reason you get a bad plan is that this rowcount estimate is so far
off:

>                ->  Index Scan using pk_table_a on table_a ta  (cost=0.00..324786.18 rows=388532 width=16) (actual
time=454.389..460.138rows=2 loops=1) 
>                      Index Cond: (a = $1)

Raising the stats target helped no doubt because it didn't overestimate
the number of rows so much...

            regards, tom lane