Svetlin Manavski <svetlin.manavski@xxxxxxxxx> writes: > I am really surprised to see that the planner needs me to explicitly specify > the same condition twice like this: > SD.detectorid = SS.detectorid > and SD.sessionid = SS.id > and SD.detectorid = 1 > and SD.sessionid >= 1001000000000::INT8 and SD.sessionid <= > 2001000000000::INT8 > and SS.detectorid = 1 > and SS.id >= 1001000000000::INT8 and SS.id <= 2001000000000::INT8 The planner does infer implied equalities, eg, given A = B and B = C it will figure out that A = C. What you are asking is for it to derive inequalities, eg infer A < C from A = B and B < C. That would be considerably more work for considerably less reward, since the sort of situation where this is helpful doesn't come up very often. On balance I don't believe it's a good thing for us to do: I think it would make PG slower on average because on most queries it would just waste time looking for this sort of situation. (In this example, the SS.detectorid = 1 clause is in fact unnecessary, since the planner will infer it from SD.detectorid = SS.detectorid and SD.detectorid = 1. But it won't infer the range conditions on SS.id from the range conditions on SD.sessionid or vice versa.) regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
