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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4214) Inconsistent metadata for CLOBGETSUBSTRING, depending on your upgrade trajectory
Date Thu, 07 May 2009 18:40:45 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4214?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12707034#action_12707034
] 

Rick Hillegas commented on DERBY-4214:
--------------------------------------

Thanks for those answers, Kristian. You have verified that a 10.5.1 engine will only send
back the smaller number of characters, regardless of what the metadata says. I am still struggling
to understand the following question:

Suppose I have two 10.5.1 databases:

F - This is a freshly created 10.5.1 database. Here the metadata is correct and the engine
doesn't send back more than 10890 characters per request.

H - This is database which was originally created with 10.4 and was then hard-upgraded to
F. Here the metadata is incorrect but the engine still doesn't send back more than 10890 characters
per request.

Concerning the performance improvement introduced by DERBY-3769, how do CLOB reads differ
between F and H?

Thanks,
-Rick

> Inconsistent metadata for CLOBGETSUBSTRING, depending on your upgrade trajectory
> --------------------------------------------------------------------------------
>
>                 Key: DERBY-4214
>                 URL: https://issues.apache.org/jira/browse/DERBY-4214
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.4.3.0, 10.5.1.1, 10.5.1.2, 10.6.0.0
>            Reporter: Rick Hillegas
>
> The on-disk signature of CLOBGETSUBSTRING changed as a result of the work done on DERBY-3769.
Previously, the return type of that function was VARCHAR(32672). The return type changed to
VARCHAR(10890) with revision 707097, which made it into release 10.5.1.1. That change was
also backported to the 10.4 branch at 711548. However, no upgrade logic was written to support
this metadata change. As a result, we have two discrepancies with our upgrade policy:
> 1) If you upgrade a database to 10.5.1.1, the signature of CLOBGETSUBSTRING will not
be the signature which you would see in a freshly created 10.5.1.1 database. Presumably this
means that the problem addressed by DERBY-3769 is not solved in upgraded databases.
> 2) If we create another release on the 10.4 branch, then we will have a change in on-disk
metadata introduced by a bug-fix release.
> I see two solutions:
> A) Add metadata upgrade logic to the 10.4 and 10.5 branches so that DERBY-3769 will be
fixed in upgraded databases as well as freshly created databases. This will violate our policy
of not changing on-disk metadata in maintenance releases.
> B) Correct the metadata in the hard-upgrade logic of 10.6. We may want to revert the
10.4 backport.
> In any event, we may also want to re-open DERBY-3769 to indicate that the bug is not
fixed in hard-upgraded databases but only in freshly created databases.
> What are people's thoughts about how to address this discrepancy?

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