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https://issues.apache.org/jira/browse/DERBY-2998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12523179
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Thomas Nielsen commented on DERBY-2998:
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First off, we will need support for unnamed windows for this jira to be
completed
I'm off on the deep end of the pool, and could use some help and/or input on
completing the prototype patch...
I have extended the grammar, handling the row_number() function as an option in
selectSubList(). Might not be the ideal place for all olap functions, but let's
leave it there for the prototype patch.
The basic idea is that bytecode is generated for the extended QueryTreeNode
classes in the nodetree, and the bytecode will be run when the statement is
actually executed after optimization. First I tried using the count aggregate
as a "template" for row_number(). I learned a lot about how aggregates work in
derby, but it weered off in the wrong direction.
Second attempt introduce a new RowNumberColumNode that extends ConstantNode,
hoping to assign an incremental number when building the ResultSet.
ResultSetList.generateCore() seems to be the place where this should be done?
Is there some existing machinery that I should/can hook into for doing the
incrementation, like the autoincrement functionality for insert? Would it be
better to extend from VirtualColumnNode instead of ConstantNode since the
column isn't actually stored?
My knowledge of the inner workings of derby are still fairly limited, and there
isn't really a lot on the wiki on this except the header, so your help is
greatly appreciated.
> 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
>
> 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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