Hello, I've recently been busy improving a query that yields a fixed number of random records matching certain conditions. I have tried all the usual approaches, and although they do work, they're all limited in some way and don't translate really well to what you "want". They're kludges, IMHO. The methods I've tried are explained quite well on http://people.planetpostgresql.org/greg/index.php?/archives/40-Getting-random-rows-from-a-database-table.html All these methods involve calculating a random number for every record in the result set at some point in time, which is really not what I'm trying to model. I think the database should provide some means to get those records, so... Dear Santa, I'd like my database to have functionality analogue to how LIMIT works, but for other - non-sequential - algorithms. I was thinking along the lines of: SELECT * FROM table WHERE condition = true RANDOM 5; Which would (up to) return 5 random rows from the result set, just as LIMIT 5 returns (up to) the first 5 records in the result set. Or maybe even with a custom function, so that you could get non-linear distributions: SELECT * FROM table WHERE condition = true LIMIT 5 USING my_func(); Where my_func() could be a user definable function accepting a number that should be (an estimate of?) the number of results being returned so that it can provide pointers to which rows in the resultset will be returned from the query. Examples: * random(maxrows) would return random rows from the resultset. * median() would return the rows in the middle of the result set (this would require ordering to be meaningful). What do people think, is this feasable? Desirable? Necessary? If I'd have time I'd volunteer for at least looking into this, but I'm working on three projects simultaneously already. Alas... Regards, Alban Hertroys. -- Alban Hertroys alban@xxxxxxxxxxxxxxxxx magproductions b.v. T: ++31(0)534346874 F: ++31(0)534346876 M: I: www.magproductions.nl A: Postbus 416 7500 AK Enschede // Integrate Your World // ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
