Hi, Query planning via GEQO currently can yield a different plan on every invokation of the planner due to its non-exhaustive nature.
This often can be inconvenient because at times there may be a very bad plan. It also makes it very hard to reproduce a problem with GEQO. [PATCH 1/3] Add erand48() implementation for non-unixoid systems. I could not find any suitable PRNG with a visible/changeable state for windows. Currently random() on windows is mapped to drand48() copied out of FreeBSD. I copied erand48(state) from there as well. As I have no windows with a buildsystem available at the moment this is untested on windows! [PATCH 2/3] Support a 'geqo_seed' GUC to make planning via GEQO repeatable. This patch adds a GUC geqo_seed to control whether the PRNG should be repeatable or not. If geqo_seed = 0 a global/per-backend state is used, thus the planning is not repeatable. If set to a value in (0,1] that number is used to initialize the generator on every planning. It adds a "void *join_search_private" variable to PlannerInfo to hold the random number generator. This variable could also be used by a join_order plugin. Alternatively it would be possible to start passing GeqoEvalData around everywhere, but the suggestion to extend PlannerInfo came from Tom... "PlannerInfo *root" is now passed to all non-static geqo related functions. It seems cleaner to do this for all functions than only functions internally using the random generator. GeqoEvalData, which is sparsely used, is replaced GeqoPrivateData which is passed via join_search_private. [PATCH 3/3] Document geqo_seed variable. I will submit this to the commitfest. I guess thats OK? Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
