"David Witham" <[EMAIL PROTECTED]> writes: > One of the customers is quite large (8.3% of the records):
Hmm. Unless your rows are quite wide, a random sampling of 8.3% of the table would be expected to visit every page of the table, probably several times. So the planner's cost estimates do not seem out of line to me; an indexscan *should* be slow. The first question to ask is why the deviation from reality. Are the rows for that customer ID likely to be physically concentrated into a limited number of physical pages? Do you have so much RAM that the whole table got swapped in, eliminating the extra I/O that the planner is expecting? regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org