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http://issues.apache.org/jira/browse/DERBY-326?page=comments#action_12362123 ]
Tomohito Nakayama commented on DERBY-326:
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I upload DERBY-326_4.patch.
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Description of patch :
* Remove processing to expand data from InputStream of blob/clob to memory
before sending to client.
* Implement layer B streaming at NetworkServer.
* As written in this issue firstly, almost rewrite whole
org.apache.derby.impl.drda.DDMWriter#writeScalarStream.
Here , "almost" means that code was not wrote from scratch, but was
wrote as reform.
Remarkable point is as next :
Original code was using variable "bytesToRead" to handle remaining
amount of data sent and remaining roon in DSS segment .
Now this variable "bytesToRead" was removed from.
New code, instead, have variable "spareDssLength" to handle remaining
room in DSS segment .
* Add call to ensureLength in writeScalarStream expecting appropriate
buffer size.
* Move comment in java/drda/org/apache/derby/impl/drda/DDMWriter.java
about client driver implementation
to java/client/org/apache/derby/client/net/Request.java.
* Modify org.apache.derby.impl.drda.EXTDTAInputStream to stream
InputStream retrieved from ResultSet directly.
* The source stream is read twice, first for seeing whether source
stream is/is not empty, second for streaming it.
* To keep reference to valid stream, EXTDTAInputStream have reference to
resultset and blob/clob also.
* Modify master file of result for blobclob4BLOB.
* Now as same as result of embed driver, dead lock will be happen in
clobTest92.
* Different expected exception was happen in negative test in
blobclob4BLOB.
* Added asserting code.
Testing :
* Executed derbyall and did not found new error.
> 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 Server, Network Client, Performance
> Reporter: Kathey Marsden
> Assignee: Tomohito Nakayama
> Attachments: DERBY-326.patch, DERBY-326_2.patch, DERBY-326_3.patch,
> DERBY-326_4.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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