Alex Stapleton <[EMAIL PROTECTED]> writes: > l1_historical=# \d "N_intra_pkey" > Index "N_intra_pkey" > Column | Type > --------+----------------------------- > symbol | text > time | timestamp without time zone > unique btree (primary key)
> and on queries like this > select * from "N_intra" where symbol='SOMETHING WHICH DOESNT EXIST' > order by time desc limit 1; This was just covered in excruciating detail yesterday ... You need to write order by symbol desc, time desc limit 1 to get the planner to recognize the connection to the sort order of this index. Since you're only selecting one value of symbol, the actual output doesn't change. > Oh, we are running 7.4.2 btw. And our random_page_cost = 1 I'll bet lunch that that is a bad selection of random_page_cost, unless your database is so small that it all fits in RAM. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq