Tanuj Khurana created PHOENIX-6899:
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Summary: Query limit not enforced in UncoveredIndexRegionScanner
Key: PHOENIX-6899
URL: https://issues.apache.org/jira/browse/PHOENIX-6899
Project: Phoenix
Issue Type: Improvement
Affects Versions: 5.1.3, 5.2.0
Reporter: Tanuj Khurana
Assignee: Tanuj Khurana
If the select query specifies a limit, the limit is available as a scan
attribute BaseScannerRegionObserver.INDEX_LIMIT
(https://github.com/apache/phoenix/blob/master/phoenix-core/src/main/java/org/apache/phoenix/iterate/RegionScannerFactory.java#L154).
However, that limit is not enforced on the page size used in the
UncoveredIndexRegionScanner. It continues to use the page size based on the
config *_phoenix.index.page_size_in_rows_*
This results in doing extra work in reading the index rows and then joining
them with the data table only to be thrown away. Set the page size to be the
smaller of the configured size and the query limit if provided.
Another thing I found was that the explain plan when the uncovered index is
used doesn't list the plan step "*SERVER <> ROW LIMIT*"
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