EXPLAIN ANALYZE much slower than running query normally
От | Chris Hutchinson |
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Тема | EXPLAIN ANALYZE much slower than running query normally |
Дата | |
Msg-id | IDEOKBCDGGIDOBADNGAPGEFEGBAA.chris@hutchinsonsoftware.com обсуждение исходный текст |
Ответы |
Re: EXPLAIN ANALYZE much slower than running query normally
Re: EXPLAIN ANALYZE much slower than running query normally |
Список | pgsql-performance |
Running a trivial query in v7.4.2 (installed with fedora core2) using EXPLAIN ANALYZE is taking considerably longer than just running the query (2mins vs 6 secs). I was using this query to quickly compare a couple of systems after installing a faster disk. Is this sort of slowdown to be expected? Here's the query: ---------------------------------------- [chris@fedora tmp]$ time psql dbt << ENDSQL > select count(*) from etab; > ENDSQL count --------- 9646782 (1 row) real 0m6.532s user 0m0.005s sys 0m0.002s [chris@fedora tmp]$ time psql dbt << ENDSQL > explain analyze select count(*) from etab; > ENDSQL QUERY PLAN ---------------------------------------------------------------------------- --------------- ----------------------------- Aggregate (cost=182029.78..182029.78 rows=1 width=0) (actual time=112701.488..112701.493 rows=1 loops=1) -> Seq Scan on etab (cost=0.00..157912.82 rows=9646782 width=0) (actual time=0.053..578 59.120 rows=9646782 loops=1) Total runtime: 112701.862 ms (3 rows) real 1m52.716s user 0m0.003s sys 0m0.005s --------------------------------------- Thanks in advance for any clues. Chris Hutchinson
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