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https://issues.apache.org/jira/browse/DERBY-2998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12572556#action_12572556
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A B commented on DERBY-2998:
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I have not had a chance to look at patch 17 yet, but I just had some follow-up
feedback based on your recent comments:
> I'm not too satisfied with the variable name 'level' but it was the best I
> could think of...
I think even something naive like "windowFunctionLevel" would be fine for now.
I'd rather avoid the generic name "level" since there is already a "level"
field that exists in FromTable.java, of which WindowNode is an indirect
subclass (so if you're debugging, two different "level" fields show up).
> That again calls into the chain of WindowResultSets and PRNs, and eventually
> ends up in a a BulkTableScanResultSet.getNextRowCore() or similar to
> actually fetch *one* row.
If the intent is to fetch exactly *one* row, then would it be beneficial to
disable bulk fetching on the base table? Otherwise, WindowResultSet may only
want to fetch a single a row but, due to bulk fetching, we could end up with 16
(or whatever the bulk size is). Not a huge problem by any means, but a
potential point for improvement if you haven't already dealt with it (maybe you
have and I just missed it).
> It seems we don't take the fact that we know we have an ascending column
> into consideration any more (we used to). I'll have to have another look at
> this.
Is this something that has been fixed with patch 17? Or is it still work in
progress? (I haven't tried it out yet).
> Add support for ROW_NUMBER() window function
> --------------------------------------------
>
> Key: DERBY-2998
> URL: https://issues.apache.org/jira/browse/DERBY-2998
> Project: Derby
> Issue Type: Sub-task
> Components: SQL
> Reporter: Thomas Nielsen
> Assignee: Thomas Nielsen
> Priority: Minor
> Attachments: d2998-10.diff, d2998-10.stat, d2998-11.diff,
> d2998-12.diff, d2998-12.stat, d2998-13.diff, d2998-13.stat, d2998-14.diff,
> d2998-14.stat, d2998-15.diff, d2998-15.stat, d2998-16.diff, d2998-16.stat,
> d2998-17.diff, d2998-17.stat, d2998-4.diff, d2998-4.stat, d2998-5.diff,
> d2998-5.stat, d2998-6.diff, d2998-6.stat, d2998-7.diff, d2998-7.stat,
> d2998-8.diff, d2998-8.stat, d2998-9-derby.log, d2998-9.diff, d2998-9.stat,
> d2998-doc-1.diff, d2998-doc-1.stat, d2998-test.diff, d2998-test.stat,
> d2998-test2.diff, d2998-test2.stat, d2998-test3.diff, d2998-test3.stat,
> d2998-test4.diff, d2998-test4.stat, d2998-test6.diff, d2998-test7.diff
>
>
> As part of implementing the overall OLAP Operations features of SQL
> (DERBY-581), implement the ROW_NUMBER() window function.
> More information about this feature is available at
> http://wiki.apache.org/db-derby/OLAPRowNumber
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