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From "Rick Hillegas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2487) Enhance Derby with EXPLAIN Functionality
Date Fri, 06 Mar 2009 15:17:56 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12679611#action_12679611

Rick Hillegas commented on DERBY-2487:

Thanks for working on this issue, Bryan. Like Knut and yourself, I am a little concerned that
we are creating many system catalogs for one feature. I like the idea that the plan-capturing
tables should be created on-demand in a user schema. You could imagine adding a new overload
of syscs_util.syscs_set_runtimestatistics:

   call syscs_util.syscs_set_runtimestatistics( 'myStatisticsSchema' )

This would

1) Create myStatisticsSchema (owned by the current user) if it didn't already exist.

2) Create the plan-bearing tables in myStatisticsSchema if they didn't already exist or if
their shape is stale. I think that the contract should be that the layout of these tables
can change between feature releases. That is, plans are not guaranteed to survive across upgrade.
Derby reserves the right to drop and recreate these tables after upgrade. Regardless of where
we put the statistics, I think that plans from previous releases should be flushed after upgrade--from
painful previous experience at Sybase I can report that you don't want to be responsible for
persisting plans across upgrade boundaries.

3) Stuff a reference to myStatisticsSchema into the LCC as you suggest. The contract is that
plans are dumped into the latest schema specified by a syscs_set_runtimestatistics command
issued in your session.

Garbage-collecting uninteresting statistics would then just be a matter of dropping a schema.

> Enhance Derby with EXPLAIN Functionality
> ----------------------------------------
>                 Key: DERBY-2487
>                 URL: https://issues.apache.org/jira/browse/DERBY-2487
>             Project: Derby
>          Issue Type: New Feature
>          Components: SQL
>    Affects Versions:
>            Reporter: Felix Beyer
>            Assignee: Bryan Pendleton
>            Priority: Minor
>         Attachments: Derby physical XPLAIN schema.png, incorporateTrunkChanges.diff,
removeSourceDepth.diff, RSProtocolNew.pdf, rts.xls, small logical xplain schema.pdf, startRegressionTest.diff,
startRegressionTest.diff, startUpgradeTests.diff, updateRegressionTests.diff, updateRegressionTests.diff,
usage.txt, xplain_patch_v1.txt, xplainClasses.pdf
> This enhancement extends Derby with EXPLAIN functions. Users want to have more feedback
than they`re getting with the current RuntimeStatistics facility. This extension is based
on the RuntimeStatistics/ResultSetStatistics functions / classes. 

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