-postgres version -> 8.4.4 -os -> redhat 5.6 -specs ->24 cores, 96GB ram, shared_buffers=32 GB -postgresql.conf -> i havent made any changes as far as the query tuning parameters are concerned. #------------------------------------------------------------------------------ # QUERY TUNING #------------------------------------------------------------------------------ # - Planner Method Configuration - #enable_bitmapscan = on #enable_hashagg = on #enable_hashjoin = on #enable_indexscan = on #enable_mergejoin = on #enable_nestloop = on #enable_seqscan = on #enable_sort = on #enable_tidscan = on # - Planner Cost Constants - #seq_page_cost = 1.0 # measured on an arbitrary scale #random_page_cost = 4.0 # same scale as above #cpu_tuple_cost = 0.01 # same scale as above #cpu_index_tuple_cost = 0.005 # same scale as above #cpu_operator_cost = 0.0025 # same scale as above effective_cache_size = 50GB # - Genetic Query Optimizer - #geqo = on #geqo_threshold = 12 #geqo_effort = 5 # range 1-10 #geqo_pool_size = 0 # selects default based on effort #geqo_generations = 0 # selects default based on effort #geqo_selection_bias = 2.0 # range 1.5-2.0 # - Other Planner Options - #default_statistics_target = 100 # range 1-10000 #constraint_exclusion = partition # on, off, or partition #cursor_tuple_fraction = 0.1 # range 0.0-1.0 #from_collapse_limit = 8 #join_collapse_limit = 8 # 1 disables collapsing of explicit # JOIN clauses -------------------------------------------------------------------------------------------------------------- if any other parameters are relative to my question pls tell me which you want and i can post them (i can post the whole postgresql.conf if it's helpful). my shared buffers ar my question apart from the specific example, is a little more general. so, is it normal to expect such an index to be used? can i write the query in another form so as to use this index? is it for example that the conditions are '>' and not '=' a factor why the index is not used? -- View this message in context: http://postgresql.1045698.n5.nabble.com/cannot-use-multicolumn-index-tp4802634p4802871.html Sent from the PostgreSQL - performance mailing list archive at Nabble.com. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance