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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 Fri, 16 Apr 2010 14:16:25 GMT

    [ https://issues.apache.org/jira/browse/DERBY-4587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12857821#action_12857821
] 

Bryan Pendleton commented on DERBY-4587:
----------------------------------------

Hi! I think you are interpreting the XPLAIN table information accurately.
You can find additional information about the tables and columns of the XPLAIN
tables here:
http://db.apache.org/derby/docs/dev/tuning/ctun_xplain_tables.html
http://db.apache.org/derby/docs/dev/ref/rrefsysxplain_statements.html
http://db.apache.org/derby/docs/dev/ref/rrefsysxplain_statement_timings.html
http://db.apache.org/derby/docs/dev/ref/rrefsysxplain_resultsets.html
http://db.apache.org/derby/docs/dev/ref/rrefsysxplain_resultset_timings.html
http://db.apache.org/derby/docs/dev/ref/rrefsysxplain_scan_props.html
http://db.apache.org/derby/docs/dev/ref/rrefsysxplain_sort_props.html

>  the query which tries to retrieve XPLAIN tables itself, is also stored in the XPLAIN
tables again

Yes, this is expected behavior. To stop collecting XPLAIN information, call
the SET_XPLAIN_SHCEMA system procedure again, with an empty argument:
http://db.apache.org/derby/docs/dev/ref/rref_syscs_set_xplain_schema.html

> 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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