[jira] [Created] (DRILL-1874) Text reader should allow treating empty fields as NULLs instead of empty string

["Aman Sinha (JIRA)" <ji...@apache.org>]

Aman Sinha created DRILL-1874:
---------------------------------

             Summary: Text reader should allow treating empty fields as NULLs instead of empty string
                 Key: DRILL-1874
                 URL: https://issues.apache.org/jira/browse/DRILL-1874
             Project: Apache Drill
          Issue Type: Bug
    Affects Versions: 0.7.0
            Reporter: Aman Sinha


The text reader treats a record as a repeated varchar and if there is an empty field it produces an empty string.   This prevents CASTing the field to a numeric type because one can get a NumberFormatException.   This is a pain point for many use cases because empty fields occur frequently in text files. 

Ideally, based on some configuration setting, we should allow treating empty fields as NULL values instead of empty string.  This will allow cast to work correctly.  

In the meantime, here's a rewrite that can be used as workaround:   
{code}
0: jdbc:drill:zk=local> select case when columns[17] = '' then cast(null as int) else cast(columns[17] as int) end  from dfs.tmp.`sample2.tbl`;
+------------+
|   EXPR$0   |
+------------+
| 5          |
| null       |
+------------+
{code}



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