On Fri, 8 Aug 2003 16:53:48 -0700, Sean Chittenden <[EMAIL PROTECTED]> wrote: >the problem with your patch was >that it picked an index less often than the current code when there >was low correlation.
Maybe bit rot? What version did you apply the patch against? Here is a new version for Postgres 7.3.4: http://www.pivot.at/pg/16d-correlation_734.diff The only difference to the previous version is that for (nKeys = 1; index->indexkeys[nKeys] != 0; nKeys++) is now replaced with for (nKeys = 1; nKeys < index->ncolumns; nKeys++) Don't know whether the former just worked by chance when I tested the 7.3.2 version :-(. Tests with 7.4Beta1 showed that index correlation comes out too low with the old loop termination condition. Anyway, the latter version seems more robust. In my tests the new index_cost_algorithms (1, 2, 3, 4) gave consistently lower cost estimates than the old method (set index_cost_algorithm = 0), except of course for correlations of 1.0 or 0.0, because in these border cases you get always min_IO_cost or max_IO_cost, respectively. Care to re-evaluate? BTW, there's a version of the patch for 7.4Beta1 (http://www.pivot.at/pg/16d-correlation_74b1.diff) which also applies cleanly against cvs snapshot from 2003-08-17. Servus Manfred ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
