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https://issues.apache.org/jira/browse/DERBY-2998?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12536986
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Thomas Nielsen commented on DERBY-2998:
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When I execute the "normal" query on a table without an index
ij> select * from (select row_number() as r, t.* from t) as tr where r < 2;
With this query I get a BasicNoPutResultSet, that in turn uses the same
BulkTableScanResultSet for fetching the rows as the index query above.
However, BasicNoPutResultSet does not take any restrictions into consideration
at all. The execution is not stopped but continues on with the full table scan.
The restriction for the resultset is enforced at a higher level.
Two options stand out for moving this ahead:
1)
extend the current BasicNoPutResultSet to take the restrictions (if any) into
consideration.
2)
A better approach might be to create a new NoPutResultSet subclass
("OLAPResultSet"?) that will use the getNextRowCore() approach of
IndexRowFromBaseRowResultSet. I have a hunch there will be other scenarios
where one would need an "OLAPResultSet" when we proceed with other subtasks of
the OLAP functionallity (DERBY-581), and this would probably give the lesser
amount of clutter to the existing ResultSet classes?
> 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-2c.diff,
> row_number_prototype-2c.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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