Hi, On 2014-03-20 16:58:42 +0000, Tom Lane wrote: > Again fix initialization of auto-tuned effective_cache_size. > > The previous method was overly complex and underly correct; in particular, > by assigning the default value with PGC_S_OVERRIDE, it prevented later > attempts to change the setting in postgresql.conf, as noted by Jeff Janes. > We should just assign the default value with source PGC_S_DYNAMIC_DEFAULT, > which will have the desired priority relative to the boot_val as well as > user-set values. > > There is still a gap in this method: if there's an explicit assignment of > effective_cache_size = -1 in the postgresql.conf file, and that assignment > appears before shared_buffers is assigned, the code will substitute 4 times > the bootstrap default for shared_buffers, and that value will then persist > (since it will have source PGC_S_FILE). I don't see any very nice way > to avoid that though, and it's not a case to be expected in practice. > The existing comments in guc-file.l look forward to a redesign of the > DYNAMIC_DEFAULT mechanism; if that ever happens, we should consider this > case as one of the things we'd like to improve.
This still is pretty ugly. Couldn't we just have a function in costsize.c that returns the actual value and computes it based on NBuffers if set to -1? Which is also called by a show_hook? Greetings, Andres Freund -- Andres Freund http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-committers mailing list ([email protected]) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-committers
