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From "Tomohito Nakayama (JIRA)" <derby-...@db.apache.org>
Subject [jira] Commented: (DERBY-326) Improve streaming of large objects for network server and client
Date Mon, 10 Apr 2006 14:00:14 GMT
    [ http://issues.apache.org/jira/browse/DERBY-326?page=comments#action_12373852 ] 

Tomohito Nakayama commented on DERBY-326:
-----------------------------------------

I resumed issues on next mail.
http://mail-archives.apache.org/mod_mbox/db-derby-dev/200603.mbox/<440C3DDE.3080306%40basil.ocn.ne.jp>

For Issue 1) and 2) , I added next ASSERT code and execute derbyall.
+    protected void writeScalarStream (boolean chainedWithSameCorrelator,
 									  int codePoint,
 									  int length,
 									  java.io.InputStream in,
 									  boolean writeNullByte) 
 		throws DRDAProtocolException
 	{
+	    
+	    // Test code to confirm InputStream is always EXTDTAInputStream
+	    if( SanityManager.DEBUG ){
+		SanityManager.ASSERT( in instanceof EXTDTAInputStream );
+	    }
+		

The result was that I found no error resulted from this ASSERT code.

Considering this result, I think it would be possible to remove code for byte[] in DRDAConnThread.writeEXTDTA
(DRDAStatement stmt), assuming stream is always EXTDTAInputStream object.

Please give me comments from other members.

> 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: ClobTest.zip, DERBY-326.patch, DERBY-326_2.patch, DERBY-326_3.patch, DERBY-326_4.patch,
DERBY-326_5.patch, DERBY-326_5_indented.patch, DERBY-326_6.patch, ReEncodedInputStream.java.modifiedForLongRun
>
> 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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