Hi >> I thought hash indexes were discouraged over btree. Anyway, I'll test it. > > Absolutely. You do not want to be using Hash Indexes these days - stick with > B-Tree. The hash refers to the method by which the executor matches the two > column fields and is not related to the underlying index type.
Yeah, I know that btrees are the preferred way - except for the match case "=". That's at least what docu. implicitly says: http://www.postgresql.org/docs/9.0/static/indexes-types.html So the note there is incomplete? > Caution: Hash index operations are not presently WAL-logged, so hash > indexes might need to be rebuilt with REINDEX after a database crash. > They are also not replicated over streaming or file-based replication. > For these reasons, hash index use is presently discouraged. ... and should also note, that hashes even don't outperform btrees for = operator? Yours, S. 2011/2/8 Mark Cave-Ayland <mark.cave-ayl...@siriusit.co.uk>: > On 08/02/11 11:05, Jorge Arévalo wrote: > >> 2011/2/8 Stefan Keller<sfkel...@gmail.com>: >>> >>> " Hash Cond: (TABLE_C.STR_FIELD = TABLE_B.STR_FIELD)" >>> tells me that these two longish strings are compared first. >>> Did you already try to index TABLE_C.STR_FIELD and TABLE_B.STR_FIELD >>> as hash instead btree? >> >> I thought hash indexes were discouraged over btree. Anyway, I'll test it. > > Absolutely. You do not want to be using Hash Indexes these days - stick with > B-Tree. The hash refers to the method by which the executor matches the two > column fields and is not related to the underlying index type. > > > ATB, > > Mark. > > -- > Mark Cave-Ayland - Senior Technical Architect > PostgreSQL - PostGIS > Sirius Corporation plc - control through freedom > http://www.siriusit.co.uk > t: +44 870 608 0063 > > Sirius Labs: http://www.siriusit.co.uk/labs > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
