Re: Transaction commits VS Transaction commits (with parallel) VS query mean time

Hi Haribabu,

The latest patch fails while applying header files part. Kindly rebase.

The patch looks good to me. However, I wonder what are the other scenarios
where xact_commit is incremented because even if I commit a single
transaction with your patch applied the increment in xact_commit is > 1. As
you mentioned upthread, need to check what internal operation resulted in
the increase. But the increase in xact_commit is surely lesser with the
patch.

postgres=# BEGIN;
BEGIN
postgres=# select xact_commit from pg_stat_database where datname =
'postgres';
xact_commit
-------------
158
(1 row)

postgres=# explain analyze select * from foo where i = 1000;
QUERY
PLAN
------------------------------------------------------------------------------------------------------------------------
Gather (cost=1000.00..136417.85 rows=1 width=37) (actual
time=4.596..3792.710 rows=1 loops=1)
Workers Planned: 2
Workers Launched: 2
-> Parallel Seq Scan on foo (cost=0.00..135417.75 rows=1 width=37)
(actual time=2448.038..3706.009 rows=0 loops=3)
Filter: (i = 1000)
Rows Removed by Filter: 3333333
Planning Time: 0.353 ms
Execution Time: 3793.572 ms
(8 rows)

postgres=# commit;
COMMIT
postgres=# select xact_commit from pg_stat_database where datname =
'postgres';
xact_commit
-------------
161
(1 row)

--
Rahila Syed
Performance Engineer
2ndQuadrant
http://www.2ndQuadrant.com <http://www.2ndquadrant.com/>
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