Hi,
I noticed the estimated rows of the base relations during the join
searching is *very* different from the estimations in the final plan.
Join search (rows of the initial_rels):
RELOPTINFO (ct): rows=1 width=4
RELOPTINFO (it): rows=1 width=4
RELOPTINFO (mc): rows=17567 width=32
RELOPTINFO (mi_idx): rows=1380035 width=8
RELOPTINFO (t): rows=2528356 width=25
The final plan:
Seq Scan on company_type ct
(cost=0.00..1.05 rows=1 width=4)
Seq Scan on info_type it
(cost=0.00..2.41 rows=1 width=4)
Parallel Seq Scan on movie_companies mc
(cost=0.00..37814.90 rows=7320 width=32)
Parallel Seq Scan on movie_info_idx mi_idx
(cost=0.00..13685.15 rows=575015 width=8)
Index Scan using title_pkey on title t
(cost=0.43..0.58 rows=1 width=25)
By looking at the joinrel->rows, I would expect relation t to have
the largest size, however, this is not true at all. I wonder what's
causing this observation, and how to get estimations close to the
final plan?
Thank you,
Donald Dong