Hello.
I corrected the upload comment.
"DERBY-326_3.patch" in previous comment was mistaken.
"DERBY-326_4.patch" is correct.
Best regards.
Tomohito Nakayama (JIRA) wrote:
[ 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
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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
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.
--
/*
Tomohito Nakayama
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