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https://issues.apache.org/jira/browse/DERBY-3002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12723093#action_12723093
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Knut Anders Hatlen commented on DERBY-3002:
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Hi Bryan,
Thanks for adding all the test cases. I haven't dived into the details of the
latest patch, but I have a couple of questions:
The patch changes how we compute aggregates for the non-rollup case as well,
and a comment in the patch says that the old technique was efficient. Have you
planned to run tests to verify that we don't introduce any performance
regressions for non-rollup group bys?
Some of the run-time statistics for existing queries have changed, returning
more rows from the sorts. Is that expected?
What are the memory requirements for the in-memory hash table? Does it hold one
copy of every unique value in the table/query? Can it run out of memory if the
query accesses a very large table?
> Add support for GROUP BY ROLLUP
> -------------------------------
>
> Key: DERBY-3002
> URL: https://issues.apache.org/jira/browse/DERBY-3002
> Project: Derby
> Issue Type: New Feature
> Components: SQL
> Affects Versions: 10.4.1.3
> Reporter: Bryan Pendleton
> Assignee: Bryan Pendleton
> Priority: Minor
> Attachments: fixWhiteSpace.diff, IncludesASimpleTest.diff,
> passesRegressionTests.diff, prototypeChangeNoTests.diff,
> rewriteGroupByRS.diff, rollupNullability.diff, useLookahead.diff
>
>
> Provide an implementation of the ROLLUP form of multi-dimensional grouping
> according to the SQL standard.
> See http://wiki.apache.org/db-derby/OLAPRollupLists for some more detailed
> information about this aspect of the SQL standard.
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