Vitalii Tymchyshyn <tiv...@gmail.com> wrote: > the simplest option that will make most people happy would be to > have a limit (waitable semaphore) on backends actively executing > the query. That's very similar to the admission control policy I proposed, except that I suggested a limit on the number of active database transactions rather than the number of queries. The reason is that you could still get into a lot of lock contention with a query-based limit -- a query could acquire locks (perhaps by writing rows to the database) and then be blocked waiting its turn, leading to conflicts with other transactions. Such problems would be less common with a transaction limit, since most common locks don't persist past the end of the transaction. -Kevin
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