Hello, pt., 29 maj 2020 o 15:56 Josh Fisher <jfis...@jaybus.com> napisał(a):
> On 5/29/2020 5:23 AM, Radosław Korzeniewski wrote: > > Hello Alan, > > śr., 27 maj 2020 o 17:02 Alan Brown <a.br...@ucl.ac.uk> napisał(a): > >> Database connections are _supposed_ to be stateless. >> > > I'm very surprised about the above statement as I cannot imagine such > functionality already available in any SQL database I'm familiar with. > If you drop a connection to the database in the middle of the transaction > then your transaction will rollback. So, no it is not a > stateless connection. > Or I misunderstood your statement. > > > It is stateful by definition, since information is stored. (The client is > authenticated, etc.) Also, there are distinct states after connecting; > waiting to issue, issue query, wait for answer, then back to waiting to > issue. A query is atomic, from the client's perspective, so must fail if > the connection is dropped prior to the answer. > Right. So, I do not understand that it could be such an expectation like above for stateless database connection. > However, while in the 'waiting to issue' state a re-connect is certainly > possible, so a dropped connection while in the wait state does not have to > be fatal. Checking connection state before each query would result in > painfully slow performance, but it should be done once just before the > catalog updates for a job are made. If a job is acquiring a db connection > at job start, then there may be quite some time between the start of the > job and actually updating the catalog. It would be more robust for the time > between the db connectivity check and the actual issuing of queries to be > made as short as possible, because it lowers the probability of a dropped > connection interrupting the job. > I never denied it and never defended the current state in this area. best regards -- Radosław Korzeniewski rados...@korzeniewski.net
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