Re: Way to use count() and LIMIT?

Поиск
Список
Период
Сортировка
От Mitch Vincent
Тема Re: Way to use count() and LIMIT?
Дата
Msg-id 014b01c18844$64f75910$0200000a@Mitch
обсуждение исходный текст
Ответ на Re: Way to use count() and LIMIT?  ("SHELTON,MICHAEL (Non-HP-Boise,ex1)" <michael_shelton@non.hp.com>)
Ответы Re: Way to use count() and LIMIT?  (Martijn van Oosterhout <kleptog@svana.org>)
Список pgsql-general
> I gather the reason you don't actually run the whole query is because the
> resultset would be too large? But you still want the database to work out
> exactly how many there are.

Not really because it's too large but because there isn't a need.. Imagine
your favorite search engine, you search and the results are displayed "X
Matches, displaying matches 1 to 10"... Same thing here -- at least that's
what my need was... The query executed could get really stout (there were
over 60 searchable fields across a variety of tables with hundreds of
thousands of records in some) so executing the count() query, then the other
certainly added the overhead... A cursor wasn't usable in this situation
because the user could chose to search once, having only ten results
displayed of 10,000 and leave the page (thus leaving me with an open
cursor).....

But again, I see no solution to the above problem and understandably so, if
you LIMIT a result set, you *limit* it -- asking it to contradict itself
doesn't make any sense so I never complained that it wasn't possible :-)

-Mitch


В списке pgsql-general по дате отправления:

Предыдущее
От: Martijn van Oosterhout
Дата:
Сообщение: Re: Way to use count() and LIMIT?
Следующее
От: Martijn van Oosterhout
Дата:
Сообщение: Re: Way to use count() and LIMIT?