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From "A B (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-2998) Add support for ROW_NUMBER() window function
Date Thu, 06 Mar 2008 17:24:58 GMT

    [ https://issues.apache.org/jira/browse/DERBY-2998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12575788#action_12575788
] 

A B commented on DERBY-2998:
----------------------------

> I do not have any more work lined up on this for 10.4. 

Okay, thanks Thomas!

The reason I asked is because on Feb 25 I posted a bunch of comments, of which #8 mentioned
how predicates on a ROW_NUMBER() do *not* actually limit rows from store, and thus such a
restriction will probably not meet the performance expectations of the user who specifies
it.  For reference, the example query was:

    SELECT * FROM (
      SELECT row_number() over () as r, t.* FROM T
    ) AS tmp WHERE r <= 3;

for which the plan shows the following for the top-most ProjectRestrictResultSet:

  ******* Project-Restrict ResultSet (1):
  Number of opens = 1
  Rows seen = 1280
  Rows filtered = 1277
  restriction = true

So we actually read all 1280 rows from disk, then filtered 1277 of them out so that, in the
end, we only returned 3 rows.

In response to that you wrote (on Feb 26):

Thomas> It seems we don't take the fact that we know we have an ascending column
Thomas> into consideration any more (we used to). I'll have to have another look at this.

So is it safe to say that this will *not* be addressed for 10.4?  That's perfectly fine, I
just want to make sure we're clear on that (esp. so that if users ask, we can give a clear
answer :)  Do you think it would be worth it to file a separate enhancement Jira for that
particular task?  (or is there one already?)

> 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, d2998-18.diff, d2998-18.stat,
d2998-19.diff, d2998-19.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-doc-2.diff, d2998-doc-2.stat, d2998-followup-2.diff,
d2998-followup-2.stat, d2998-followup-distinct.diff, d2998-followup-distinct.diff, d2998-followup-distinct.stat,
d2998-followup-doc3.diff, d2998-followup-doc3.stat, d2998-followup-issue1.diff, d2998-followup-issue1.stat,
d2998-followup-issue4.diff, d2998-followup-issue4.stat, d2998-followup-removeunused.diff,
d2998-followup-testsuite.diff, d2998-followup-testsuite.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, d2998-test8.diff, d2998-test9.diff,
rreffuncrownumber.html
>
>
> 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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