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Posted to dev@calcite.apache.org by "Liya Fan (Jira)" <ji...@apache.org> on 2020/09/10 07:13:00 UTC

[jira] [Created] (CALCITE-4241) Some improvements to metadata query

Liya Fan created CALCITE-4241:
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             Summary: Some improvements to metadata query
                 Key: CALCITE-4241
                 URL: https://issues.apache.org/jira/browse/CALCITE-4241
             Project: Calcite
          Issue Type: Improvement
          Components: core
            Reporter: Liya Fan
            Assignee: Liya Fan


# For RelMdColumnUniqueness#areColumnsUnique(RelSubset, RelMetadataQuery,
 ImmutableBitSet, boolean), we can return early as we encounter the first null.
 # For RelMdDistinctRowCount#getDistinctRowCount(Values, RelMetadataQuery,
 ImmutableBitSet, RexNode), we can get the distinct row count accurately, instead of guessing that half of the elements are distinct. 
 # In class RelMdUtil, areColumnsDefinitelyUnique and areColumnsDefinitelyUniqueWhenNullsFiltered have identical behaviors, so we should use the formmer, which is more efficient. 



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