David Mullineux <dmullx@xxxxxxxxx> writes: > But my question is, why does 'analyze verbose' report that it has scanned > '30000 of NNNN pages, containing NNNN live rows and 0 dead rows; 30000 rows > in sample,....' > As most tables would store more than 1 row per page, I expected that 30000 > rows would require a lot fewer than 30000 *pages* to be scanned. Why is it > saying it's scanned 30000 pages instead of only 30000 rows ? If the table is sufficiently large, taking a sample of a single row from each of 30000 different pages is the correct behavior. Taking more than one row from each of a smaller set of pages would give a nonrandom (because clumped) sample. regards, tom lane
