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https://issues.apache.org/jira/browse/DERBY-2998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12533104
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Thomas Nielsen commented on DERBY-2998:
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Working my way through the optimization of the simple query:
select * from (select row_number() as r, t.* from t) as tr where r < 2;
I see that during preprocessing the WHERE clause is converted to a
PredicateList. The predicate BinaryOperatorNode (my '<' lessThan) is
successfully categorize()'d as pushable, which is a good thing!
However, ProjectRestrictNode.pushExpressionsIntoSelect() in
PRN.pushExpressions() does not do anything. I would have thought this was where
the predicate would be pushed into the select subquery.
As a side note DERBY-649 seems to have fixed a similar issue by pushing
predicates into UnionNodes. Investigation ongoing.
> 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: row_number_prototype-2b.diff,
> row_number_prototype-2b.stat
>
>
> 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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