berkaysynnada opened a new pull request, #8094:
URL: https://github.com/apache/arrow-datafusion/pull/8094

   ## Which issue does this PR close?
   
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   Partially closes #8078.
   
   ## Rationale for this change
   
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   After `enum Precision` is introduced in DF, some bugs are discovered. This 
PR resolves 3 bugs:
   1) singleton check for `ColumnStatistics`,
   2) limit in datasource with num rows statistics,
   3) min - max exactness of columns with constant value,
   and refactors the `statistics()` of limit.
   
   ## What changes are included in this PR?
   
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   1st fix: A column is labeled as singleton only if its min and max values are 
exact and equal.
   2nd fix: To stop processing, only exact count of rows is regarded. 
Otherwise, we should continue to process until range estimation of precision 
implemented.
   3rd fix: During the analysis in filter statistics, if a column is filtered 
with a constant value (e.g. c=1), we set its min and max values as exact.
   
   ## Are these changes tested?
   
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   Yes, with existing tests.
   
   ## Are there any user-facing changes?
   
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