On Wed, 2007-10-10 at 17:00 +0200, Cédric Villemain wrote: > <snip> > Reading the manual, you can learn that prepared statement can (not) > follow the same plan as direct query: > the plan is make before pg know the value of the variable. > > See 'Notes' http://www.postgresql.org/docs/8.2/interactive/sql-prepare.html Thanks, had missed that, however, I am afraid that I fail to see how preparing a query using PQprepare() and then executing it using PQexecPrepared(), is 8 thousand times slower than directly executing it.,, ( 403386.583ms/50.0ms = 8067 ). When doing a 'manual' prepare and explain analyze I get the following rascal=# prepare cq (char(12), smallint, integer) as SELECT oid, calllog_mainteng, calllog_phase, calllog_self FROM calllog WHERE calllog_mainteng = $1 AND calllog_phase = $2 AND calllog_self < $3 OR calllog_mainteng = $1 AND calllog_phase < $2 ORDER BY calllog_mainteng DESC, calllog_phase DESC, calllog_self DESC limit 25; PREPARE rascal=# explain analyze execute cq ('124 ', 8, 366942); QUERY PLAN --------------------------------------------------------------------------- Limit (cost=0.00..232.73 rows=25 width=26) (actual time=2.992..3.178 rows=25 loops=1) -> Index Scan Backward using calllog_rmc_idx on calllog (cost=0.00..38651.38 rows=4152 width=26) (actual time=2.986..3.116 rows=25 loops=1) Index Cond: (calllog_mainteng = $1) Filter: (((calllog_phase = $2) AND (calllog_self < $3)) OR (calllog_phase < $2)) Total runtime: 3.272 ms So I suspect that there is something more fundamental here... -- Regards Theo ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
