FileBasedStatisticsReportableInputFormat (Flink : Table : Common 2.0-preview1 API)

```
@PublicEvolving
public interface FileBasedStatisticsReportableInputFormat
```
Extension of input format which is able to report estimated statistics for file based connector.
This interface is used by file-based connectors which should also implement SupportsStatisticReport. Since file have different formats, and each format has a different way of storing and obtaining statistics information. For example: for Parquet and Orc, they both store the metadata information in the file footer, which including row count, max/min, null count, etc. While, for csv, there is no other metadata information excluding file size, one approach to estimate row count is: the entire file size divided by the average length of the sampled rows.
Note: This method is called at plan optimization phase, the implementation of this interface should be as light as possible, but more complete information.

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`TableStats`	`reportStatistics(List<org.apache.flink.core.fs.Path> files, DataType producedDataType)`	Returns the estimated statistics of this input format.

- Method Detail
  - reportStatistics
```
TableStats reportStatistics(List<org.apache.flink.core.fs.Path> files,
                            DataType producedDataType)
```
    Returns the estimated statistics of this input format.
    
    Parameters:
    
    files - The files to be estimated.
    
    producedDataType - the final output type of the format.