Re: sub select performance due to seq scans - Mailing list pgsql-performance

H Hale <hhale21@rogers.com> writes:
>     ->  Bitmap Heap Scan on flatomfilesysentry  (cost=2.00..274.38 rows=3238 width=30) (actual time=0.011..0.013
rows=1loops=6473) 
>           Recheck Cond: (flatomfilesysentry.objectid = "outer".dstobj)
>           ->  Bitmap Index Scan on flatomfilesysentry_pkey  (cost=0.00..2.00 rows=3238 width=0) (actual
time=0.007..0.007rows=1 loops=6473) 
>                 Index Cond: (flatomfilesysentry.objectid = "outer".dstobj)

Well, there's our estimation failure: 3238 rows expected, one row
actual.

What is the data distribution of flatomfilesysentry.objectid?
It looks from this example like it is unique or nearly so,
but the planner evidently does not think that.

            regards, tom lane