Re: Re: Proposal to fix Statement.executeBatch()

> 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,
> René Pijlman
>
>