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From Kristian Waagan <Kristian.Waa...@Sun.COM>
Subject Enforcing length restrictions for streams of unknown length
Date Wed, 02 Aug 2006 16:43:05 GMT
Hello,

My initial work on the new JDBC4 length less overloads are approaching 
completion, but I still have one issue that must be solved.

Currently, streams with unknown length are materialized to determine the 
length. This is the approach I have implemented in the client driver in 
lack of a better solution at the moment. But, the approach is also used 
in the embedded driver, and this is simply not good enough.

If I pass the stream down to the storage layer, bypassing the length 
checks done by the data type classes (SQLBinary, SQLBlob etc), the 
storage layer will insert all the data it can get. For instance, I can 
insert 3KB into a 2KB Blob column.
To solve this, I plan to wrap the user/application stream in a 
limit-stream. This stream will cause an exception to be thrown if it has 
read more data than can be allowed in the column it is being inserted into.

In addition to the maximum length issue, there is also that of 
truncation of trailing blanks. I don't yet fully understand what I have 
to change. Much of the functionality I need is already in place, but 
some changes might be required. For instance, the column width and 
whether truncation is allowed or not might need to be passed down to the 
limit-mechanism.

Questions, suggestions or other feedback is appreciated!



Related issues are DERBY-1473 and DERBY-1417.
I plan to finish this for 10.2.



Thanks,
-- 
Kristian

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