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From "Sunitha Kambhampati (JIRA)" <derby-...@db.apache.org>
Subject [jira] Updated: (DERBY-326) Improve streaming of large objects for network server and client
Date Tue, 17 Jan 2006 06:44:43 GMT
     [ http://issues.apache.org/jira/browse/DERBY-326?page=all ]

Sunitha Kambhampati updated DERBY-326:
--------------------------------------

    Attachment: ClobTest.zip

Thanks Tomohito for the patch.   I wanted to try a simple clob test with reads and see if
there was any difference performance wise. But I could not apply the latest patch cleanly
maybe because some changes were submitted today.  I have attached a zip file with the test
file and a script to run it.  Currently the test inserts clob of size ~500k and then does
read of all the rows in the table.  It would be great if you could run it before and after
your changes to see the difference.   Please feel free to make changes to the test or change
the parameters to the test.   Thanks. 

> Improve streaming of large objects for network server and client
> ----------------------------------------------------------------
>
>          Key: DERBY-326
>          URL: http://issues.apache.org/jira/browse/DERBY-326
>      Project: Derby
>         Type: Improvement
>   Components: Network Client, Performance, Network Server
>     Reporter: Kathey Marsden
>     Assignee: Tomohito Nakayama
>  Attachments: ClobTest.zip, DERBY-326.patch, DERBY-326_2.patch, DERBY-326_3.patch, DERBY-326_4.patch,
DERBY-326_5.patch
>
> 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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