> I have a performance problem when traversing a table in index order with > multiple columns including a date column in date reverse order. Below > follows a simplified description of the table, the index and the > associated query > > \d prcdedit > prcdedit_prcd | character(20) | > prcdedit_date | timestamp without time zone | > > Indexes: > "prcdedit_idx" btree (prcdedit_prcd, prcdedit_date) Depending on how you use the table, there are three possible solutions. First, if it makes sense in the domain, using an ORDER BY where _both_ columns are used descending will make PG search the index in reverse and will be just as fast as when both as searched by the default ascending. Second possibility: Create a dummy column whose value depends on the negative of prcdedit_date, e.g., -extract(epoch from prcdedit_date), keep the dummy column in sync with the original column using triggers, and rewrite your queries to use ORDER BY prcdedit_prod, dummy_column. Third: Create an index on a function which sorts in the order you want, and then always sort using the function index (you could use the -extract(epoch...) gimmick for that, among other possibilities.) HTH.
