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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3002) Add support for GROUP BY ROLLUP
Date Wed, 02 Sep 2009 03:22:34 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12750255#action_12750255
] 

Dag H. Wanvik commented on DERBY-3002:
--------------------------------------

I found the patch accessible, easy to follow, thanks Bryan!
Interesting! Nice extension to Derby I think.

On a first pass thru I noticed little beyond missing javadocs, some
segments with 8 wide tabs, some debug printing left, which is all fine at
this stage.  The approach look solid to me. I can see the uncertainty
about the performance in the pure group by case, but I suspect that
since you do sort avoidance when possible, it is still ok, but your
performance tests should cast light on that.

I would be nice to define N in the initial comment in "then there are
N+1 entries in resultRows" in GroupedAggregateResultSet.

Did you and Knut resolve the discussion about whether the statement
"select b, sum(a) from ru where 1<>1 group by rollup(b)" should have
zero result row or one? It wasn't quite clear from reading the threads
here. The test makes an empty rs the canon in this case.

I'll dig in further into the patch logic next.


> Add support for GROUP BY ROLLUP
> -------------------------------
>
>                 Key: DERBY-3002
>                 URL: https://issues.apache.org/jira/browse/DERBY-3002
>             Project: Derby
>          Issue Type: Improvement
>          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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