David Wayne Birdsall created TRAFODION-2765:
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Summary: MDAM is not considered when sometimes it should be
Key: TRAFODION-2765
URL: https://issues.apache.org/jira/browse/TRAFODION-2765
Project: Apache Trafodion
Issue Type: Bug
Components: sql-cmp
Affects Versions: 2.3-incubating
Environment: All
Reporter: David Wayne Birdsall
Assignee: David Wayne Birdsall
The Optimizer has logic in method ScanOptimizer::useSimpleFileScanOptimizer
that tries to determine scenarios where a single subset access will clearly be
optimal, and in those scenarios does not consider MDAM. An example would be a
query whose only key predicates are equality predicates on a leading subset of
the key columns.
However, the logic in ScanOptimizer::useSimpleFileScanOptimizer sometimes rules
out considering MDAM when it would be beneficial to do so. An example is a
query with equality predicates on the first two columns of the key, no
predicates on the third, and equality on the fourth. When the UEC of the third
column is small, MDAM is likely to be the more efficient plan and should be
considered.
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