Manikandan Swaminathan <maniswami23(at)gmail(dot)com> writes:
> 4. When running the following query, I would expect the index "idx_col_b_a"
> to be used: select min(col_b) from test_table where col_a > 4996.
> I have a range-based filter on col_a, and am aggregating the result with
> min(col_b). Both columns are covered by "idx_col_b_a".
They may be covered, but sort order matters, and that index has the
wrong sort order to help with this query. Try
create index on test_table(col_b, col_a);
regards, tom lane