I've got a simple query. When I use explain analyze it lasts 7 times slower. Why?
test_counters=# SELECT COUNT(*), xtype FROM test GROUP BY xtype ORDER BY xtype;
count | xtype
---------+-------
669000 | A
84000 | B
63000 | D
15000 | E
159000 | G
7866000 | H
1000000 | N
144000 | NI
(8 rows)
Time: 3343,376 ms
test_counters=# EXPLAIN ANALYZE SELECT COUNT(*), xtype FROM test GROUP BY xtype ORDER BY xtype;
QUERY PLAN
---------------------------------------------------------------------------------------------------------------------------------
Sort (cost=243136.22..243136.24 rows=8 width=2) (actual time=24306.075..24306.083 rows=8 loops=1)
Sort Key: xtype
Sort Method: quicksort Memory: 25kB
-> HashAggregate (cost=243136.00..243136.10 rows=8 width=2) (actual time=24306.030..24306.038 rows=8 loops=1)
-> Seq Scan on test (cost=0.00..193136.00 rows=10000000 width=2) (actual time=0.013..11365.414 rows=10000000 loops=1)
Total runtime: 24306.173 ms
(6 rows)
Time: 24306,944 ms
regards
Szymon
