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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