"Robert Haas" <robertmhaas@xxxxxxxxx> writes: > It seems very strange for the planner to decide to build an in-memory > hash table on a column that is already indexed (the primary key, no > less!). What's strange about it? A probe into an in-memory hashtable is a lot cheaper than a probe into an index, so this type of plan makes plenty of sense if the hashtable will fit in RAM and there are going to be a lot of probes. (Where "a lot" means "enough to amortize the cost of building the hashtable", of course.) > Experimentation shows this is actually about 25% faster. Well, that just says your cost parameters need a bit of adjustment if you'd like the planner to get the crossover point exactly right. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
