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https://issues.apache.org/jira/browse/DERBY-6256?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13681660#comment-13681660
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Mike Matrigali commented on DERBY-6256:
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3) optimizerTracing - The new xml-style tracing is intended to help diagnose
performance problems in production. We don't currently document either style of
optimizer tracing. If we were to document the old-style optimizer trace, I
think that all we could tell people would be to send us the output. I think
that the xml-style trace could potentially be used to guide a customer to the
selection of optimizer overrides for working around a production problem.
I don't think old-style optimizer trace is production ready. It is not
documented and not tested as far as I know. On the other hand it is useful.
So as you said in the past we put this in debug code
and that made it hard for users. I assume new style is not really production
ready either, as I have not seen much testing, and we are likely looking to
improve this based on customer feedback so
would want it to not get tied to upward compatiblity at this point. Not sure
the intent.
As to where to put it, I see many embedded applications are likely to not be
able to use it at all no matter what jar, without shutting down/booting.
Others might. Again I see it as not core, but
instead optional for those that want to use it. I was ok with the performance
impact description from rick on this feature. It seemed like those not
enabling the tracing did not pay code path
price. Would be good to eliminate code bloat default price if possible.
> Move the XmlVTI into the product.
> ---------------------------------
>
> Key: DERBY-6256
> URL: https://issues.apache.org/jira/browse/DERBY-6256
> Project: Derby
> Issue Type: Improvement
> Components: SQL, Tools
> Affects Versions: 10.11.0.0
> Reporter: Rick Hillegas
> Assignee: Rick Hillegas
> Attachments: derby-6256-01-aa-move-XmlVTI-into-product.diff,
> derby-6256-02-aa-allowParentTags.diff
>
>
> The XmlVTI under derbyDemo has been useful to me for many years. It has
> become even more useful now that Derby supports varargs. That is because
> varargs make it very easy to declare an XmlVTI. At this point, I think it is
> worth re-phrasing the XmlVTI in terms of varargs and moving it into the
> product so that we can use it for internal table functions. There is no rush
> to expose XmlVTI as part of Derby's public api, but we could consider doing
> that if other people find this table function to be useful.
> The XmlVTI is a table function which turns an xml file into a tabular data
> set which you can query via sql. When you declare an XmlVTI, you state the
> following arguments:
> 1) The url of an xml file.
> 2) The name of the element in the xml file which you want to treat as a
> record or row.
> 3) The names of the attributes and subelements of that record which you want
> to treat as columns. Now that we have varargs, it is possible to represent
> this trailing argument as a variable length argument list.
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