[jira] [Created] (CALCITE-4841) Support numeric column type in CSV and File adapter

["Louis Kuang (Jira)" <ji...@apache.org>]

Louis Kuang created CALCITE-4841:
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             Summary: Support numeric column type in CSV and File adapter
                 Key: CALCITE-4841
                 URL: https://issues.apache.org/jira/browse/CALCITE-4841
             Project: Calcite
          Issue Type: Improvement
          Components: csv-adapter, file-adapter
            Reporter: Louis Kuang


Currently, the csv adapter does not support the numeric column type (see supported types in [CsvFieldType]([https://github.com/apache/calcite/blob/4bc916619fd286b2c0cc4d5c653c96a68801d74e/file/src/main/java/org/apache/calcite/adapter/file/CsvFieldType.java#L35)).] Any type that is not supported will be interpreted by the [CsvEnumerator]([https://github.com/apache/calcite/blob/master/file/src/main/java/org/apache/calcite/adapter/file/CsvEnumerator.java)] as string.    

When dealing with decimal numbers,  the currently most appropriate type is `double`. However, this is not accurate enough for financial data. This feature request proposes adding a `numeric` column type that will be implemented by the Java `BigDecimal` type (and by conversion in [JavaToSqlTypeConversionRules]([https://github.com/apache/calcite/blob/4bc916619fd286b2c0cc4d5c653c96a68801d74e/core/src/main/java/org/apache/calcite/sql/type/JavaToSqlTypeConversionRules.java#L74)] be represented as a `Decimal` SQL type). This allow financial data to be represented and computed more accurately (`BigDecimal` has higher precision than `double`).  

Will send PR later.



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