Hi, according the doc (http://www.postgresql.org/docs/8.3/interactive/runtime-config-query.html#GUC-CPU-OPERATOR-COST), Quote: Sets the planner's estimate of the cost of processing each operator or function executed during a query. i expected for a 1000 row test-table a cost per function of 2.5 (cpu_operator_cost = 0.0025), but i got 5. First, a full table scan: test=*# explain analyse select i from s_test; QUERY PLAN ------------------------------------------------------------------------------------------------------- Seq Scan on s_test (cost=0.00..15.00 rows=1000 width=4) (actual time=0.013..2.315 rows=1000 loops=1) Total runtime: 4.232 ms (2 rows) cost=15. Now, the same query but with one or two functions on a particular column: test=*# explain analyse select i, cos(i) from s_test; QUERY PLAN ------------------------------------------------------------------------------------------------------- Seq Scan on s_test (cost=0.00..20.00 rows=1000 width=4) (actual time=0.026..3.043 rows=1000 loops=1) Total runtime: 5.017 ms (2 rows) test=*# explain analyse select i, cos(i), md5(i) from s_test; QUERY PLAN ------------------------------------------------------------------------------------------------------- Seq Scan on s_test (cost=0.00..25.00 rows=1000 width=4) (actual time=0.040..5.414 rows=1000 loops=1) Total runtime: 7.444 ms (2 rows) cost increased by 5 per function-call, why, why not 2.5? Version: 8.1 Andreas -- Andreas Kretschmer Kontakt: Heynitz: 035242/47150, D1: 0160/7141639 (mehr: -> Header) GnuPG-ID: 0x3FFF606C, privat 0x7F4584DA http://wwwkeys.de.pgp.net
