[jira] [Commented] (DRILL-8071) format-excel should use POI DataFormatter

["PJ Fanning (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-8071?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17454585#comment-17454585 ] 

PJ Fanning commented on DRILL-8071:
-----------------------------------

[~cgivre] I spotted what I think is another issue in the excel code

> format-excel should use POI DataFormatter
> -----------------------------------------
>
>                 Key: DRILL-8071
>                 URL: https://issues.apache.org/jira/browse/DRILL-8071
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Execution - Data Types
>            Reporter: PJ Fanning
>            Priority: Major
>
> The existing ExcelBatchReader uses the raw data values from the cells. This raw data ignores formatting set on the cells. As an example, numbers and dates are stored as doubles. With the POI DataFormatter, you can get the cell style applied so that the data will appear as it does when you view the data in Excel itself.
> [https://poi.apache.org/apidocs/dev/org/apache/poi/ss/usermodel/DataFormatter.html#formatCellValue-org.apache.poi.ss.usermodel.Cell-]
>  
> A big number like 123456789.987654 could be stored as double that is more like 123456789.9876539999999 when represented in decimal format (because this might be the closest match that double can represent). The cell format could say that cell has 6 decimal places after the decimal point so the formatter would round the number back to the value that it displayed in Excel as.
> Even if you choose not to use the DataFormatter, you have unprotected calls to `cell.getNumericCellValue()` and that could easily throw an exception (if the data is not stored a number). Even `cell.getStringCellValue()` can throw an exception - for similar reasons.
>  
> Code that processes excel files is a real pain to get right because the Microsoft storage format is really bad.
>  



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