[jira] [Created] (CALCITE-4511) The number of distinct values for constant columns should be 1

["Liya Fan (Jira)" <ji...@apache.org>]

Liya Fan created CALCITE-4511:
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             Summary: The number of distinct values for constant columns should be 1
                 Key: CALCITE-4511
                 URL: https://issues.apache.org/jira/browse/CALCITE-4511
             Project: Calcite
          Issue Type: Improvement
          Components: core
            Reporter: Liya Fan
            Assignee: Liya Fan


Suppose we have a relation with 3 columns: {{(a, '1', '2')}}. The first column comes from an underlying table, while the other two columns are constants. 

For this relation, we should have {{NDV(1) = 1}}, since column 1 is a constant, which have only one possible value (suppose the column index starts from 0).

Similarly, we should have {{NDV(1, 2) = 1}}, since both columns are constants.

We should also have {{NDV(0, 1) == NDV(0)}}, because the number of distinct values depends on the non-const column, which is {{a}} from the underlying table. 



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