[GitHub] [spark] wangyum opened a new pull request #25214: [SPARK-28461][SQL] Pad Decimal numbers with trailing zeros to the scale of the column

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

wangyum opened a new pull request #25214: [SPARK-28461][SQL] Pad Decimal numbers with trailing zeros to the scale of the column
URL: https://github.com/apache/spark/pull/25214
 
 
   ## What changes were proposed in this pull request?
   **Spark SQL**:
   ```sql
   spark-sql> select cast(1 as decimal(38, 18));
   1
   spark-sql>
   
   scala> spark.sql("select cast(1 as decimal(38, 18))").show(false)
   +-------------------------+
   |CAST(1 AS DECIMAL(38,18))|
   +-------------------------+
   |1.000000000000000000     |
   +-------------------------+
   ```
   
   **PostgreSQL**:
   ```sql
   postgres=# select cast(1 as decimal(38, 18));
          numeric
   ----------------------
    1.000000000000000000
   (1 row)
   ```
   **Presto**:
   ```sql
   presto> select cast(1 as decimal(38, 18));
           _col0
   ----------------------
    1.000000000000000000
   (1 row)
   ```
   
   Hive fixed this issue by [HIVE-12063](https://issues.apache.org/jira/browse/HIVE-12063). This pr fix this issue. After this pr:
   ```sql
   spark-sql> select cast(1 as decimal(38, 18));
   1.000000000000000000
   ```
   
   ## How was this patch tested?
   
   unit tests
   

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