Hello
look on:
postgres=# explain select count(*) over () from x;
QUERY PLAN
-------------------------------------------------------------
WindowAgg (cost=0.00..265.00 rows=10000 width=0)
-> Seq Scan on x (cost=0.00..140.00 rows=10000 width=0)
(2 rows)
Time: 1,473 ms
postgres=# explain select count(*) over (order by a) from x;
QUERY PLAN
------------------------------------------------------------------------
WindowAgg (cost=0.00..556.25 rows=10000 width=4)
-> Index Scan using gg on x (cost=0.00..406.25 rows=10000 width=4)
(2 rows)
but
query1: 160ms
query2: 72ms
regards
Pavel Stehule
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