> Ewe. How expensive is scanning an index compared to the heap? Does > anyone have figure on that in terms of I/O and time?
See this post for an example: http://archives.postgresql.org/pgsql-performance/2006-02/msg00416.php For my 200 million table, scanning the pk index took ~ 4 hours. And then there are some more indexes... So if the index has to be scanned completely, that's still too much. Cheers, Csaba. ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
