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https://issues.apache.org/jira/browse/DERBY-2487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12701305#action_12701305
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Bryan Pendleton commented on DERBY-2487:
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I'm concerned about the patch's proposed modification to
iapi.sql.execute.RunTimeStatistics.
The patch proposes to add a reference to
impl.sql.execute.rts.ResultSetStatistics.
This seems like an indication of a layering problem; the internal
ResultSetStatistics
class should not need to be visible through this high-level interface.
The newly-added method getTopRSS() is only used in one place, in the
XPLAINSystemTableVisitor.
I'm going to investigate whether I can change this API so that it doesn't
expose the implementation class.
One idea was to replace the current API with a new one, something like:
public void acceptFromTopRSS(XPLAINVisitor v)
which would be implemented in RunTimeStatisticsImpl.java roughly as:
if (topResultSetStatistics != null)
topResultSetStatistics.accept(v);
Then the external iapi.sql.execute.RunTimeStatistics interface would only need
to be aware of
the iapi.sql.execute.xplain.XPLAINVisitor interface, which keeps the layering
cleaner, I think.
I'll give this a try and see if it works.
> 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: 10.2.2.0
> Reporter: Felix Beyer
> Assignee: Bryan Pendleton
> Priority: Minor
> Attachments: Derby physical XPLAIN schema.png,
> incorporateTrunkChanges.diff, refactorVisitor.diff, refactorVisitor.diff,
> removeSourceDepth.diff, RSProtocolNew.pdf, rts.xls, small logical xplain
> schema.pdf, startRegressionTest.diff, startRegressionTest.diff,
> startUpgradeTests.diff, updateRegressionTests.diff,
> updateRegressionTests.diff, usage.txt, userSchemaPrototyping.diff,
> userSchemaPrototyping.diff, userSchemaPrototyping.diff, 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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