Shay Rojansky <r...@roji.org> writes: >> We really do need "cancel up to" semantics for reliable behavior. >> Consider the case where the client has sent the query (or thinks it has) >> but the server hasn't received it yet. If the cancel request can arrive >> at the server before the query fully arrives, and we don't have "cancel >> all messages up through N" semantics, the cancel will not do what the >> client expects it to.
> Keep in mind that in the case of a cancellation arriving really too early, > i.e. before any messages have been received by the server, it will be > totally ignored since at the time of reception there's nothing for the > server to cancel yet. Right, that's how it works today ... > This may seem a bit exotic, although if you really > want to provide air-tight cancellation semantics you could have the server > track unfulfilled cancellation requests. In other words, if the server > receives "cancel up to X" and is now processing X-5, the cancellation > request is kept in memory until X has been duly cancelled. Exactly my point. If we're trying to make cancel semantics less squishy, I think we need to do that; errors in this direction are just as bad as the late-cancel-arrival case. regards, tom lane -- Sent via pgsql-hackers mailing list (email@example.com) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers