"Trevor Talbot" wrote: >On 8/16/07, Rainer Bauer <usenet@xxxxxxxxxx> wrote: > >> >> But if you go to eBay, they always give you an accurate count. Even if the no. >> >> of items found is pretty large (example: <http://search.ebay.com/new>). >> > >> >And I'd bet money that they're using a full text search of some kind to >> >get those results, which isn't remotely close to the same thing as a >> >generic SELECT count(*). >> >> Without text search (but with a category restriction): >> <http://collectibles.listings.ebay.com/_W0QQsacatZ1QQsocmdZListingItemList> >> >> I only wanted to show a counter-example for a big site which uses pagination >> to display result sets and still reports accurate counts. > >Categories are still finite state: you can simply store a count for >each category. Again it's just a case of knowing your data and >queries; it's not trying to solve a general infinite-possibilities >situation. Consider this query with multiple WHERE conditions: <http://search.ebay.com/ne-ol-an_W0QQfasiZ1QQfbdZ1QQfcdZ1QQfcidZ77QQfclZ3QQfmcZ1QQfrppZ50QQfsooZ1QQfsopZ1QQftidZ1QQpriceZ1QQsabdhiZ100QQsacurZ999QQsalicZQ2d15QQsaprchiZ50000QQsatitleZQ28neQ2aQ2colQ2aQ2canQ2aQ29QQsojsZ0> My point is that whatever search criterias are involved and how many items are found eBay always returns the *accurate* number of items found. Before this drifts off: * I do know *why* count(*) is slow using Postgres. * I *think* that count(*) is fast on eBay because count is cheaper using Oracle (which eBay does: <http://www.sun.com/customers/index.xml?c=ebay.xml>). * I realize that pagination for multi-million tuple results does not make sense. Rainer ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to majordomo@xxxxxxxxxxxxxx so that your message can get through to the mailing list cleanly
