Re: streaming result sets: progress - Mailing list pgsql-jdbc

Nic,

Here are my thoughts on this topic.

1) Since the server doesn't support cursors across transactions, I don't
think the driver should either.  In fact in jdbc3 the DatabaseMetaData
object has a supportsResultSetHoldability() method that explicitly lets
the driver tell the application what is does/doesn't support in this area.

I think running multiple sql statements to mimic this behavior is a very
bad idea.  Since the select statements will run at different times they
will return different data (since they will pick up commited changes
between runs), and if you don't include an order by the results are
completely unpredictable.  If someone wants this very unpredictable
behavior they can issue the multiple statements themselves.

2) I think the use of cursors should be optional.  In fact since most
queries don't need them since most queries return a small number of rows
, I think the use of cursors needs to be turned on.  I think there
should be two ways to do this:  the first is by setting the fetchSize()
and the second would be a jdbc url parameter.

3) I think the transaction characteristics of the current patch are just
fine and conform to the jdbc specification.  The code should
automatically close the resultset when a commit occurs.  One thing that
will be confusing is that noncursor based result sets will work accross
commits, but cursor based ones won't.  But I think that is reasonable.

thanks,
--Barry


Nic Ferrier wrote:
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> Haris Peco <snpe@snpe.co.yu> writes:
>
>
>>I have tried.
>>DatabaseMetaData is fine, but ResultSet.[get|set]FetchSize don't
>>work
>
>
> What error do you get?
>
>
>>Prepared command don't work, but my greatest problem are trasnaction
>>I hope that cursor in 7.4 will be out of a transaction
>
>
> I don't think there's much I can do about the cursor problem.
>
>
>
>
>>Can Yoy yet another :
>>set driver's flag btw jdbc:pgsql:...?cursor=yes
>>for use cursor or old way
>
>
> What does everyone else think? Is a system doing a different query
> each time worth looking into?
>
>
> Nic
>
>
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