Hi all,
I'm testing a proprietary driver that connects my old applications to a
postgresql database. The problem is that I've got very strange issues about
execution times. For instance, the following query:
cogedb=> explain analyze SELECT * FROM GMMOVART WHERE DATA >= '01/01/2006'
AND DATA <= '31/12/2006' ORDER BY DATA, CONTATORE, RIGA;
QUERY PLAN
------------------------------------------------------------------------------------------------------------------------------------------------
Sort (cost=152440.12..152937.79 rows=199069 width=340) (actual
time=1734.550..1827.006 rows=214730 loops=1)
Sort Key: data, contatore, riga
-> Bitmap Heap Scan on gmmovart (cost=6425.18..134919.15 rows=199069
width=340) (actual time=135.161..721.679 rows=214730 loops=1)
Recheck Cond: ((data >= '2006-01-01'::date) AND (data <=
'2006-12-31'::date))
-> Bitmap Index Scan on gmmovart_index03 (cost=0.00..6375.42
rows=199069 width=0) (actual time=128.400..128.400 rows=214730 loops=1)
Index Cond: ((data >= '2006-01-01'::date) AND (data <=
'2006-12-31'::date))
Total runtime: 1893.026 ms
(7 rows)
Executes in 1,8 seconds. Now, the same query launched thru the driver produces
a log with the following entry:
cogedb LOG: duration: 5265.103 ms statement: SELECT * FROM GMMOVART WHERE
DATA >= '01/01/2006' AND DATA <= '31/12/2006' ORDER BY DATA, CONTATORE, RIGA
with a duration of 5,2 seconds, that is 3+ times longer than the query run in
the psql prompt! Please note that the query is always executed locally.
Now, I don't have access to driver internals, so I don't know how it works and
what could be the difference of time due to. Is there something I can work on
my postgresql server in order to better investigate or to tune to shrink down
execution times?
I suspect that the driver uses a cursor, could it be a "pause" between
consecutive fetches that produces such time difference? Please note that I've
tested different queries with similar results, even among database restarts (in
order to avoid result caching).
Any help is appreciated.
cogedb=> select * from version();
version
----------------------------------------------------------------------------------------------------------------------
PostgreSQL 8.2.9 on i486-pc-linux-gnu, compiled by GCC cc (GCC) 4.1.3
20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)
(1 row)
Thanks,
Luca
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