Understanding EXPLAIN ANALYZE estimates when loops != 1 - Mailing list pgsql-general

From Philip Semanchuk
Subject Understanding EXPLAIN ANALYZE estimates when loops != 1
Date
Msg-id 5A55FB13-6DE3-4F5E-A951-65EF83EF0161@americanefficient.com
Whole thread Raw
Responses Re: Understanding EXPLAIN ANALYZE estimates when loops != 1  (David Rowley <dgrowleyml@gmail.com>)
List pgsql-general
Hi all,
I could use some help interpreting EXPLAIN ANALYZE output.

->  Index Scan using ix_foo on t1 (cost=0.69..68.57 rows=3283 width=105) (actual time=0.006..0.918 rows=3760 loops=94)

The actual rows returned by this plan node ~= 3760 * 94 = 353,440. Did postgres expect (estimate) 3283 rows from this
join,or 3283 * 94 = 308,602?  


Same question for this node.

->  Parallel Index Scan using pk_xyz on xyz  (cost=0.29..2354.67 rows=54285 width=25) (actual time=0.049..6.326
rows=14864loops=5) 

Actual rows ~= 14864 * 5 = 74,320, estimate = 54285 or 54285 * 5?


THanks
Philip


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