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From "Bryan Pendleton (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-4587) Add tools for improved analysis and understanding of query plans and execution statistics
Date Thu, 15 Apr 2010 14:08:49 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12857326#action_12857326
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Bryan Pendleton commented on DERBY-4587:
----------------------------------------

Thanks Nirmal! It seems like there is general consensus that this technique
can be used to build a useful tool.

I had originally anticipated that the data would be fetched from the XPLAIN
tables as simple Java data types, then emitted as a single XML document by
the tool, but I think your suggestion to use XMLSERIALIZE is intriguing.

Each time we ran a statement such as SELECT XMLSERIALIZE(c) FROM xpl
we'd get a little "XML fragment", is that right? Or would get get an entire
XML document at that point?

What would be needed to "stitch together" these XML fragments, or collection
of smaller XML documents, into a single larger XML document representing
the entire query plan in its XML-formatted form?

That is, in pseudocode-outline, what might that process look like in the tool code?


> Add tools for improved analysis and understanding of query plans and execution statistics
> -----------------------------------------------------------------------------------------
>
>                 Key: DERBY-4587
>                 URL: https://issues.apache.org/jira/browse/DERBY-4587
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL, Tools
>            Reporter: Bryan Pendleton
>            Assignee: Bryan Pendleton
>         Attachments: Derby Query Plan Screen Shot 2.jpg, Derby_Query_Plan_Screen_Shot.jpg,
PostgreSQL license.jpg, Read_Me.txt, Source.rar
>
>
> I think it would be great to see some work in the area of tools for helping
> with the analysis of complex query execution. Quite frequently, users of
> Derby have trouble comprehending (a) how their query is being translated
> into a query plan by the optimizer, and (b) what the execution-time resource
> usage of the various parts of the query is.
> There are low-level features in Derby which capture this information and
> record it, such as logQueryPlan, and the XPLAIN tables, but there is a lot
> of opportunity for designing higher-level tools which can process the query
> plan and execution statistics information and present it in a more
> comprehensible fashion. 

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