Improve streaming of large objects for network server and client
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Key: DERBY-326
URL: http://issues.apache.org/jira/browse/DERBY-326
Project: Derby
Type: Improvement
Components: Network Server, Network Client, Performance
Reporter: Kathey Marsden
Currently the stream writing methods in network server and client require a
length parameter. This means that we have to get the length of the stream
before sending it. For example in network server in EXTDTAInputStream we have
to use getString and getbytes() instead of getCharacterStream and
getBinaryStream so that we can get the length.
SQLAM Level 7 provides for the enhanced LOB processing to allow streaming
without indicating the length, so, the writeScalarStream methods in
network server DDMWriter.java and network client Request.java can be changed to
not require a length.
Code inspection of these methods seems to indicate that while the length is
never written it is used heavily in generating the DSS. One strange thing is
that it appears on error, the stream is padded out to full length with zeros,
but an actual exception is never sent. Basically I think perhaps these methods
need to be rewritten from scratch based on the spec requirements for lobs.
After the writeScalarStream methods have been changed, then EXTDAInputStream
can be changed to properly stream LOBS. See TODO tags in this file for more
info. I am guessing similar optimizations available in the client as well, but
am not sure where that code is.
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