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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3847) Tuning Guide lacks information on turning off Derby property settings
Date Fri, 29 Aug 2008 15:08:44 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12627000#action_12627000

Dag H. Wanvik commented on DERBY-3847:

Ah yes, sigh.. this is really confusing.

> So I guess if you had previously set a system-wide property
> programmatically, then set it database-wide, then set the
> database-wide version to null, the previous programmatic system-wide
> setting would take effect. 

Yes, that was what I was thinking of.

> If there was none, the default for the
> database-wide property would take effect. Or would it? Would you
> then slip down to the derby.properties file setting if there was
> one?

Looking at the code in PropertyUtil.java it would then slip down to
derby.properties (cf. logic in getPropertyFromSet), correct.

> There's also the fact that some properties have *only* system scope
  or only database scope.

As far as I can tell, this is orthogonal to how the value is
established. I think it is good to explain all these intricacies in one place.

> Tuning Guide lacks information on turning off Derby property settings
> ---------------------------------------------------------------------
>                 Key: DERBY-3847
>                 URL: https://issues.apache.org/jira/browse/DERBY-3847
>             Project: Derby
>          Issue Type: Bug
>          Components: Documentation
>    Affects Versions:
>            Reporter: Kim Haase
>            Assignee: Kim Haase
>            Priority: Minor
>         Attachments: ctunproper22250.html, ctunproper22250.html, DERBY-3847-2.diff, DERBY-3847.diff
> The documentation of how to turn off Derby properties is spotty. Dag Wanvik reports that
"I checked the code, and when you set a database property to a null value, that property is
removed from the list of database properties; i.e. the situation is back to where you were
before it was first set, so the built-in defaults apply again (or system properties if there
are any)."
> The behavior for turning off user settings is slightly different and is documented in
several places; it's the general case that seems to be missing. This information needs to
be added to the description of Derby properties in the Tuning Guide, probably in the general
topic "Derby properties" (http://db.apache.org/derby/docs/dev/tuning/ctunproper22250.html).

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