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https://issues.apache.org/jira/browse/TRAFODION-2765?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Wayne Birdsall updated TRAFODION-2765:
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Fix Version/s: 2.3-incubating
> 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
> Fix For: 2.3-incubating
>
>
> 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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