[GitHub] [spark] NobiGo commented on pull request #35220: [SPARK-37922][SQL] Improve `SimplifyCasts` to remove useless cast

[GitBox <gi...@apache.org>]

NobiGo commented on pull request #35220:
URL: https://github.com/apache/spark/pull/35220#issuecomment-1014426755


   In the Postgresql:
   ```
   CREATE TABLE decimalTable(value numeric(7,2));
   INSERT INTO decimalTable(value) VALUES (12.34);
   INSERT INTO decimalTable(value) VALUES (12.45);
   INSERT INTO decimalTable(value) VALUES (12.55);
   
   select value::decimal(5,1)::decimal(4,2) from decimalTable;
   ```
   ```
   value
   12.30
   12.50
   12.60
   ```
   
   If we simplify this cast to value::decimal(4,2) The value will be:
   
   ```
   value
   12.34
   12.45
   12.55
   ```
   
   The result will be different. So it is reasonable or acceptable in Spark?


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