Parquet silently discards decimal values if they do not fit in declared type

If I declare a schema with a DecimalType(7,2) and I try and write a value that will not fit, such as 123,456.00 and then read it back, I get a null value i.e. the data is silently discarded.

I have written up a full example to demonstrate this, here:

https://github.com/andygrove/spark-parquet-decimal-bug

**Environment**: Ubuntu 15.10
**Reporter**: [Andy Grove](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=andygrove) / @andygrove

_{**Note**: *This issue was originally created as [PARQUET-578](https://issues.apache.org/jira/browse/PARQUET-578). Please see the [migration documentation](https://issues.apache.org/jira/browse/PARQUET-2502) for further details.*}

未指定源文件或测试。首先运行 issue 中链接的完整示例，并比较写入和读取一个超出 DecimalType(7,2) 的值；当超出范围的小数得到显式处理，而不是被静默返回为 null 时，即表示完成。

由索引模型根据 Issue 内容生成。