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From "Lance J. Andersen" <Lance.Ander...@Sun.COM>
Subject Re: question on IN parameter values and streams ?
Date Mon, 26 Sep 2005 16:35:01 GMT
i am talking to the EG about clarifying this in the spec.


Daniel John Debrunner wrote:

>Sunitha Kambhampati wrote:
>>I have a question about the binding of parameters using the stream api's
>>in JDBC
>>If you set the value for a parameter marker of a preparedstatement to a
>>stream by using the stream api's like setBinaryStream, what should be
>>the expected behavior on subsequent executions of the preparedstatement.
>>ps.setBinaryStream(2,mystream, streamLength);   //mystream is a user
>>supplied stream
>>for (int i = start; i < start + rows; i++) {
>>          ps.setInt(1, i);
>>          count += ps.executeUpdate();
>>      }
>>Since the value set is a stream, the first execution will read off the
>>stream and the stream will be drained. In case of Derby, if the
>>preparedstatement is an insert, subsequent inserts will actually throw
>>an error as the stream will not have enough data.
>>I looked at the jdbc 3.0 spec, api and the tutorial book (edition 2) but
>>didnt find anything specific to streams and how they should be treated
>>when binding. ____________
>>1) Is it ok to expect the user  to supply the stream each time when
>>using the stream api's provided we document it clearly.
>>2)or should we check to see if the user supplied stream supports the
>>markSupported() and reset the stream each time we finish reading it.
>>3) or store the data from the stream on disk for multiple re-use
>>4) materialize the stream so it can be used multiple times
>>I think #1 seems fine to me compared to all the other options unless of
>>course the standard has something specific to say.
>>Thoughts/comments ?
>Good question, first just worry about the functional behaviour as seen
>by the JDBC client, not the implementation. So really 2,3,4 are the
>same, the parameter value set by a stream is re-used for the next execution.
>The only item I see in the JDBC 3.0 spec is the last paragraph of 13.2.2
>which basically says parameters are re-used. Nothing special called out
>about streams.
>There is a potential clue in the javadoc for
>"In general, parameter values remain in force for repeated use of a
>Maybe we could take that "In general" to mean, "except for streams".
>I think at least option 1) is a safe solution that is forwards
>compatible with allowing a value set by a stream value to be reused. The
>error could be better by clearing the 'parameter is set' flag after the
>execution if the value was set by a stream.

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