Hi all,
I want to find out how PG gets rows when it explains a query.
For example, when I issue:
explain select count(*) from pg_class where relname='pg_class';
QUERY PLAN
--------------------------------------------------------------
Aggregate (cost=4.55..4.55 rows=1 width=0)
-> Seq Scan on pg_class (cost=0.00..4.55 rows=1 width=0)
Filter: (relname = 'pg_class'::name)
(3 rows)
Where and how PG get "rows=1"?
Thank you!