closeOnCompletion

[Dave Cramer]

On Wed, 17 Feb 2021 at 13:33, Douglas Surber <douglas.surber at oracle.com>
wrote:

> I wrote the original proposal. The intent was to handle the case Lance
> described. It was not intended to allow multiple executions of the
> Statement. So while the language may not be as clear as it needs to be, the
> case Filipe described should throw on the second execution of the
> Statement. At least that was my intent.
>
>
Well there's enough hints in the wording to figure that out, but they are
just hints.
We (postgres) are going to implement it in such a way that the statement
will not be executed twice

Dave


> Douglas
> ------------------------------
> *From:* jdbc-spec-discuss <jdbc-spec-discuss-retn at openjdk.java.net> on
> behalf of Lance Andersen <lance.andersen at oracle.com>
> *Sent:* Wednesday, February 17, 2021 9:52 AM
> *To:* Dave Cramer <davecramer at gmail.com>
> *Cc:* Filipe Silva <filipe.silva at oracle.com>;
> jdbc-spec-discuss at openjdk.java.net <jdbc-spec-discuss at openjdk.java.net>
> *Subject:* Re: closeOnCompletion
>
> I will have to go dig back through my email archive as this was first
> discussed in 2009.
>
>
> The overall intent was to deal with code similar to:
>
> ----------------------
> ResultSet rs = foo();
>  while(rs.next() {
>      /*do something */
> }
> rs.close();
>
> public ResultSet foo() {
>
>    Statement stmt = con.createStatement();
>    stmt.closeOnCompletion();
>    ResultSet rs = stmt.executeQuery(aQuery);
>    return rs
>
> }
> ------------------
>
>
> We did spend a lot of time on this back in 2009 and took quite a bit of
> time to reach agreement on the current wording.  However, it does  look
> like there is the potential for some additional word smithing.
>
> Best
> Lance
>
>
>
> On Feb 17, 2021, at 12:34 PM, Dave Cramer <davecramer at gmail.com<mailto:
> davecramer at gmail.com>> wrote:
>
> On Wed, 17 Feb 2021 at 12:13, Filipe Silva <filipe.silva at oracle.com
> <mailto:filipe.silva at oracle.com>> wrote:
>
> On 17/02/21 10:53, Dave Cramer wrote:
> Interesting situation.
>
> If we have an open statement with open resultsets and call
> closeOnCompletion and then execute the statement a second time the
> statement will throw an already closed exception since the spec says that
> executing a statement a second time closes any open resultsets. Closing
> said resultsets ends up closing the statement.
>
> I'm just confirming that this is the intended behaviour. Seems about
> right
> since if you set closeOnCompletion you would not expect to re-use the
> statement.
>
> Dave Cramer
> No, I don't think it is supposed to work like this. "Completion" means
> that the user is done with the ResultSet(s) and explicitely calls
> close() on it/them.
>
> Successive executions do close previously opened ResultSets but closing
> those ResultSets implicitely (by re-executing) do not close the
> Statement. The documentation makes it clear when it says "a call to
> |closeOnCompletion| does effect both the *subsequent execution of
> statements*, (...)". There would be no "subsequent execution of
> statements" if the behavior was the one you described.
>
>
> Well interestingly I'm told that the Oracle driver does close the statement
> on subsequent execution.
>
> Either way I'm not sure I agree with the inference. Now we have to debate
> the word execution. Is calling the method an execution or is completing the
> call an execution ?
>
> Dave Cramer
>
>