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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3002) Add support for GROUP BY ROLLUP
Date Sat, 27 Jun 2009 10:12:47 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12724829#action_12724829
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Knut Anders Hatlen commented on DERBY-3002:
-------------------------------------------

Hi Bryan,

I'm not aware of any GROUP BY benchmarks that we can use, so I guess we'll have to write a
simple one ourselves. The reason why I asked was that it wasn't quite clear to me (well, it
still isn't... :)) whether your comment about aggregate sort observers being an efficient
technique meant that you thought the new technique was less efficient.

As to the hash tables, one alternative is to use a BackingStoreHashTable, which keeps the
data in a HashMap up to a certain point, after which it spills data to disk (or at least to
the page cache). It'll probably increase the overhead, though.

> 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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