closeOnCompletion
Filipe Silva
filipe.silva at oracle.com
Wed Feb 17 19:14:42 UTC 2021
Hi Douglas,
Wait, this is not the question here, there is no doubt that closing the
result sets closes the statement. The question is whether a statement
with `closeOnCompletion` and an active results set (not closed yet) can
be re-executed or not. In different words, implicit closing of open
result sets on next statement execution triggers `closeOnCompletion` and
closes the statement or should it execute?
Regards,
Filipe
On 17/02/21 19:03, Douglas Surber wrote:
> As I said I wrote the original proposal and what I intended and what
> the EG discussed at the time at least implicitly was that closing the
> open ResultSet would close the Statement and that no subsequent
> execution was possible. No this wasn't spelled out in the discussion.
> It was clearly the intent as the purpose of the method was to handle
> the case Lance described.
>
> Maybe the language is unclear but I don't think that would justify
> expanding the behavior of the method to cover your use case. The goal
> is to support a specific use case. Any change to the spec should be to
> more clearly state how that use case is supported, not to expand the
> meaning to support additional use cases, especially a use case that
> has never come up in practice.
>
> Douglas
> ------------------------------------------------------------------------
> *From:* Filipe Silva <filipe.silva at oracle.com>
> *Sent:* Wednesday, February 17, 2021 10:55 AM
> *To:* Dave Cramer <davecramer at gmail.com>; Douglas Surber
> <douglas.surber at oracle.com>
> *Cc:* Lance Andersen <lance.andersen at oracle.com>;
> jdbc-spec-discuss at openjdk.java.net <jdbc-spec-discuss at openjdk.java.net>
> *Subject:* Re: closeOnCompletion
>
> Well, looks strange to me. I explain why in the an answer I wrote in
> StackOverflow
> (https://stackoverflow.com/questions/66241480/jdbc-statement-closeoncompletion-should-close-statement-on-next-execution/66248074#66248074).
>
> Moreover, IMO, allowing re-executions doesn't conflict with the use
> case below and it allows more.
>
> Regards,
> Filipe
>
> On 17/02/21 18:38, Dave Cramer wrote:
>>
>>
>> On Wed, 17 Feb 2021 at 13:33, Douglas Surber
>> <douglas.surber at oracle.com <mailto: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
>> <mailto:jdbc-spec-discuss-retn at openjdk.java.net>> on behalf of
>> Lance Andersen <lance.andersen at oracle.com
>> <mailto:lance.andersen at oracle.com>>
>> *Sent:* Wednesday, February 17, 2021 9:52 AM
>> *To:* Dave Cramer <davecramer at gmail.com
>> <mailto:davecramer at gmail.com>>
>> *Cc:* Filipe Silva <filipe.silva at oracle.com
>> <mailto:filipe.silva at oracle.com>>;
>> jdbc-spec-discuss at openjdk.java.net
>> <mailto:jdbc-spec-discuss at openjdk.java.net>
>> <jdbc-spec-discuss at openjdk.java.net
>> <mailto: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><mailto: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><mailto: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
>>
> --
>
> Oracle <http://www.oracle.com>
> Filipe Silva, Senior Software Developer
> Mobile: +351.91.009.2110
> MySQL Middleware and Clients
> Oracle Portugal, Lagoas Park, Edifício N.º 8, 2740-244 Porto Salvo
>
>
--
Oracle <http://www.oracle.com>
Filipe Silva, Senior Software Developer
Mobile: +351.91.009.2110
MySQL Middleware and Clients
Oracle Portugal, Lagoas Park, Edifício N.º 8, 2740-244 Porto Salvo
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