Hi all, I don't fully understand how is the cost of a bitmap heap scan computed. For instance when the explain output node is similar to the following:
Bitmap Heap Scan on test (cost=17376.49..48595.93 rows=566707 width=6) Recheck Cond: ((text1 = 'A'::text) OR (text1 = 'C'::text)) Filter: (num1 > 1) how is the cost of the node (48595.93 - 17376.49) computed? I think it should be something like: (reltuples * ( index_filtering_factor_A + index_filtering_factor_B) ) * (cpu_tuple_cost + cpu_operator_cost) + (reltuples * ( index_filtering_factor_A + index_filtering_factor_B) ) / tuples_per_pages but this does not equal the optimizer cost, so I guess I'm doing something wrong. Suggestions? Thanks, Luca -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
