Re: Re: Proposal to fix Statement.executeBatch() - Mailing list pgsql-jdbc

Can someone suggest what is to be done with the propsed patch?

>  > What exactly is the behaviour of the backend in that scenario?
>  > Does it commit every separate SQL statement in the
>  > semicolon-separated list, or does it commit the list as a whole?
>  > Does it abort processing the statement list when an error occurs
>  > in one statement? And if it continues, does it return an error
>  > when only one statement in the middle of the list had an error?
>
> I do not know what the server does if you have autocommit enabled and
> you issue multiple statements in one try.  However, I would be OK with
> the driver issuing the statements one by one with autocommit on.  If you
> are running in this mode you just wouldn't get any performance improvement.
>
>  > However, it would mean a change in behaviour of the driver that
>  > may break existing JDBC applications: the driver will no longer
>  > return update counts for all statements in a batch like it
>  > currently does, it will return "unknown" for most statements.
>  > I'm not sure if the performance improvement justifies this
>  > non-backwardly-compatible change, though I agree this is the
>  > intention of the feature. What do you think?
>
> I wouldn't worry about this 'change in behavior' because if the caller
> is JDBC complient it should be coded to handle the new behavior as it is
> complient with the spec.
>
> thanks,
> --Barry
>
>
>
>
> Rene Pijlman wrote:
> > On Mon, 27 Aug 2001 11:07:55 -0700, you wrote:
> > [executeBatch() implemented as one round trip]
> >
> >>Here is how I would suggest this be done in a way that is spec
> >>compliant (Note: that I haven't looked at the patch you submited yet, so
> >>forgive me if you have already done it this way, but based on your
> >>comments in this email, my guess is that you have not).
> >>
> >
> > Indeed, I have not implemented this.
> >
> >
> >>Statements should be batched together in a single statement with
> >>semicolons separating the individual statements (this will allow the
> >>backend to process them all in one round trip).
> >>
> >>The result array should return an element with the row count for each
> >>statement, however the value for all but the last statement will be
> >>'-2'.  (-2 is defined by the spec to mean the statement was processed
> >>successfully but the number of affected rows is unknown).
> >>
> >
> > Ah, I see. I hadn't thought of that solution.
> >
> >
> >>In the event of an error, then the driver should return an array the
> >>size of the submitted batch with values of -3 for all elements. -3 is
> >>defined by the spec as the corresponding statement failed to execute
> >>successfully, or for statements that could not be processed for some
> >>reason.  Since in postgres when one statement fails (in non-autocommit
> >>mode), the entire transaction is aborted this is consistent with a
> >>return value of -3 in my reading of the spec.
> >>
> >
> > Not quite. A statement in a batch may also fail because its a
> > succesful SELECT as far as the server is concerned (can't have
> > select's in a batch). But that situation can also be handled
> > correctly by setting the update count for that particular
> > statement to -3. Its then up to the application to decide if it
> > wants to rollback, I would say.
> >
> > But what to do when an error occurs with autocommit enabled?
> > This is not recommended, but allowed by the spec, if I
> > understand it correctly.
> >
> > What exactly is the behaviour of the backend in that scenario?
> > Does it commit every separate SQL statement in the
> > semicolon-separated list, or does it commit the list as a whole?
> > Does it abort processing the statement list when an error occurs
> > in one statement? And if it continues, does it return an error
> > when only one statement in the middle of the list had an error?
> >
> >
> >>I believe this approach makes the most sense because:
> >>1) It implements batches in one round trip (the intention of the feature)
> >>2) It is complient with the standard
> >>3) It is complient with the current functionality of the backend
> >>
> >
> > If we can come up with an acceptable solution for an error with
> > autocommit enabled, I agree. Otherwise, I'm not sure.
> >
> > However, it would mean a change in behaviour of the driver that
> > may break existing JDBC applications: the driver will no longer
> > return update counts for all statements in a batch like it
> > currently does, it will return "unknown" for most statements.
> > I'm not sure if the performance improvement justifies this
> > non-backwardly-compatible change, though I agree this is the
> > intention of the feature. What do you think?
> >
> > Regards,
> > Ren? Pijlman
> >
> >
>
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 3: if posting/reading through Usenet, please send an appropriate
> subscribe-nomail command to majordomo@postgresql.org so that your
> message can get through to the mailing list cleanly
>

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026