[GitHub] [spark] pengbo opened a new pull request #24436: [SPARK-27539][SQL] Inaccurate aggregate outputRows estimation with column contains null value

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pengbo opened a new pull request #24436: [SPARK-27539][SQL] Inaccurate aggregate outputRows estimation with column contains null value
URL: https://github.com/apache/spark/pull/24436
 
 
   ## What changes were proposed in this pull request?
   This PR is follow up of https://github.com/apache/spark/pull/24286. As @gatorsmile pointed out that column with null value is inaccurate as well.
   
   ```
   > select key from test;
   2
   NULL
   1
   spark-sql> desc extended test key;
   col_name key
   data_type int
   comment NULL
   min 1
   max 2
   num_nulls 1
   distinct_count 2
   ```
   
   The distinct count should be distinct_count + 1 when the column contains null value.
   ## How was this patch tested?
   
   Existing tests & new UT added.

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