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From "Mamta A. Satoor (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (DERBY-3918) Improve transfer buffer utilization for Clobs
Date Wed, 17 Jul 2013 01:11:47 GMT

     [ https://issues.apache.org/jira/browse/DERBY-3918?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Mamta A. Satoor updated DERBY-3918:

    Urgency: Normal
     Labels: CLOB derby_triage10_11  (was: CLOB)
> Improve transfer buffer utilization for Clobs
> ---------------------------------------------
>                 Key: DERBY-3918
>                 URL: https://issues.apache.org/jira/browse/DERBY-3918
>             Project: Derby
>          Issue Type: Improvement
>          Components: JDBC, Network Server
>    Affects Versions:
>            Reporter: Kristian Waagan
>            Priority: Minor
>              Labels: CLOB, derby_triage10_11
> Read DERBY-3769 for details.
> Briefly, for Clobs containing ASCII characters the content is sent over the network in
smaller chunks than necessary. The reason is because the network server is unaware of how
many bytes a range of characters results in when they are encoded as modified UTF-8. As exceeding
the maximum size is very costly, a defensive assumption of 3 bytes per char is used. This
leads to sending only 10890 bytes over the wire per round-trip instead of up to 32672 for
ASCII content.
> The same goes for Clobs with chars encoded by 2 bytes, or Clobs with mixed content.
> A few ideas on how to solve this:
>  - read chars in chunks, look at each char to calculate byte length and read chars until
byte buffer will be filled sufficiently
>  - add new method to Engine[C]LOB
>  - rewrite implementation to work on the byte level instead of the character level (this
would be an internal API only)
>  - add and make use of more information about the Clob content, i.e. if it consists of
only 1 byte per char encodings.

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