Dean Rasheed <dean.a.rasheed@xxxxxxxxxxxxxx> writes: > 2010/1/19 Philippe Lang <philippe.lang@xxxxxxxxxxxxxx>: >> That works just fine, but is there maybe a way of creating a slighly >> more "generic" index? If I change the ">" with a "<" in the query, index >> cannot of course be used. According to documentation, answer seems to be >> "no"... > You could create an index on the difference: > create index long_transformation_index on indexed_table > ((data1-this_is_a_long_transformation(data2))); > then rewrite your queries accordingly: > ... WHERE data1-this_is_a_long_transformation(data2) > some const (or > < some const) Yeah. There's been a lot of noise in this thread about statistics, but the real problem is this: an indexable condition compares the indexed value to a constant (or at least something that doesn't change across rows). "col1 > foo(col2)" is not able to use an index on col1, nor an index on foo(col2). But if you indexed the whole expression col1 - foo(col2), you could get an index search on comparisons of that to a constant. 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
