I cannot understand why the following two queries differ so much in execution time (almost ten times)
Query A (two queries) select distinct moment.mid from moment,timecard where parent = 45 and (pid=17 and timecard.mid = moment.mid) order by moment.mid; select distinct moment.mid from moment,timecard where parent = 45 and (pbar = 0) order by moment.mid; Query B (combining the two with OR) select distinct moment.mid from moment,timecard where parent = 45 and ((pid=17 and timecard.mid = moment.mid) or (pbar = 0)) order by moment.mid; $ time psql -o /dev/null -f query-a.sql fektest real 0m2.016s user 0m1.532s sys 0m0.140s $ time psql -o /dev/null -f query-b.sql fektest real 0m28.534s user 0m1.516s sys 0m0.156s I have tested this in two different computers with different amount of RAM, fast or slow CPU, and the difference is persistent, almost ten times. I should say that this is on postgresql 7.4.16 (debian stable). Can query B be rewritten so that it would execute faster? TIA -- Hans Ekbrand (http://sociologi.cjb.net) <[EMAIL PROTECTED]> GPG Fingerprint: 1408 C8D5 1E7D 4C9C C27E 014F 7C2C 872A 7050 614E
signature.asc
Description: Digital signature
