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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Created: (DERBY-4652) Provide mean to save length information when inserting CLOBs using the JDBC 4.0 "length less overrides"
Date Wed, 12 May 2010 08:00:41 GMT
Provide mean to save length information when inserting CLOBs using the JDBC 4.0 "length less
overrides"
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                 Key: DERBY-4652
                 URL: https://issues.apache.org/jira/browse/DERBY-4652
             Project: Derby
          Issue Type: Improvement
          Components: Store
    Affects Versions: 10.7.0.0
            Reporter: Kristian Waagan


When inserting a long character stream [1] without specifying the length of the value, Derby
is currently unable to store the length of the value in the header. In certain cases this
forces Derby to decode the whole value to obtain the character length. Besides from the cost
of reading in data and decoding it, this may also affect the state of the page cache negatively
(i.e. pushing out more frequently used data).

A proposed solution to the issue is to update the header bytes in-place after the insert has
been performed. It may also be possible to use a kind of back-ground thread.
At the very least, we should provide a stored procedure or another mean to update (and/or
detect) the CLOB values which lack the header information.


[1] In this case, longer than the buffer size of the Derby input converter (char -> UTF-8,
32 KB).

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