Re: BLOB performance test FYI

On 2002-04-18 Joe Shevland wrote:

> I figured that the differences in the types and how the backend
> handles them precludes actually trying to do anything to optimise the
> behaviour in the client interface. For example, can I use the socket
> connection when performing an update operation to stream binary data to
> the backend, or does it expect the whole statement to be character data
> sent at the one time?

Hi Joe!

It's only possible to send the whole statement, data and query, as
character strings.
Today when you add a stream parameter to a PreparedStatement it
immediately reads the stream into a String. Then it concatenates the
query and the parameters into an even larger String, which is scanned
for escape codes and such (creating yet another huge String!). Finally
it's all written to the backend.

A better way would be to keep the stream parameter stored as a
InputStream until the query is executed, and then stream it directly to
the backend. This requires some changes in how the PreparedStatement
class deals with parameters and how the PreparedStatement is fed to the
backend. The escape scanning will have to be rewritten as a filtering
stream, etc.

It would imply a change in semantics of a PreparedStatement, that it
could only be executed one time once the parameters are set. But I
wouldn't be surprised if that is what the JDBC spec. says anyway.

(Today's internal interface in Connection assumes a String to be
executed. Perhaps a new interface "Query" with a "StringQuery" class to
encapsulate simple string queries and something for prepared queries
could be used. But that's only my thoughs on how to implement it).

/Anders

--

A n d e r s B e n g t s s o n | ndrsbngtssn(at)yahoo(dot)se
Stockholm, Sweden |

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