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Posted to derby-dev@db.apache.org by "Kristian Waagan (JIRA)" <ji...@apache.org> on 2008/11/04 16:50:44 UTC

[jira] Commented: (DERBY-3907) Save useful length information for Clobs in store

    [ https://issues.apache.org/jira/browse/DERBY-3907?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12644985#action_12644985 ] 

Kristian Waagan commented on DERBY-3907:
----------------------------------------

I'm a bit unsure how to handle the format id issue.

It is not clear to me what the differences between the various clob fields in StoredFormatIds are:
    - CLOB_TYPE_ID
    - CLOB_COMPILATION_TYPE_ID
    - CLOB_TYPE_ID_IMPL
    - SQL_CLOB_ID

In the current implementation, I think I need to access this information up to the JDBC level, i.e. in classes like StoreStreamClob, SQLClob and possibly a ResultSet class.
To me it seems I need two versions of the SQL_CLOB_ID, but I'm not sure.
Can anyone with more knowledge about the type system guide me?

I do think we need a new format id, because the current format  (two bytes that can have any values) makes it hard to add another stream header format.

> Save useful length information for Clobs in store
> -------------------------------------------------
>
>                 Key: DERBY-3907
>                 URL: https://issues.apache.org/jira/browse/DERBY-3907
>             Project: Derby
>          Issue Type: Improvement
>          Components: JDBC, Store
>    Affects Versions: 10.5.0.0
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>
> The store should save useful length information for Clobs. This allows the length to be found without decoding the whole data stream.
> The following thread raised the issue on what information to store, and also contains some background information: http://www.nabble.com/Storing-length-information-for-CLOB-on-disk-tp19197535p19197535.html
> The information to store, and the exact format of it, is still to be discussed/determined.
> Currently two bytes are set aside for length information, which is inadequate.

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