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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