[jira] [Created] (DRILL-7426) Json support lists of different types

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

benj created DRILL-7426:
---------------------------

             Summary: Json support lists of different types
                 Key: DRILL-7426
                 URL: https://issues.apache.org/jira/browse/DRILL-7426
             Project: Apache Drill
          Issue Type: Improvement
          Components: Documentation
    Affects Versions: 1.16.0
            Reporter: benj


With a file.json like
{code:json}
{
    "name": "toto",
    "info": [["LOAD", []]],
    "response": 1
}
{code}
A simple SELECT gives an error
{code:sql}
apache drill> SELECT * FROM dfs.test.`file.json`;
Error: UNSUPPORTED_OPERATION ERROR: In a list of type VARCHAR, encountered a value of type LIST. Drill does not support lists of different types.
{code}
But there is an option _exec.enable_union_type_ that allows these request
{code:sql}
apache drill> ALTER SESSION SET `exec.enable_union_type` = true;
apache drill> SELECT * FROM dfs.test.`file.json`;
+------+---------------+----------+
| name |     info      | response |
+------+---------------+----------+
| toto | [["LOAD",[]]] | 1        |
+------+---------------+----------+
1 row selected (0.283 seconds)
{code}
The usage of this option is not evident. So, it will be useful to mention after the error message the possibility to set it.
{noformat}
Error: UNSUPPORTED_OPERATION ERROR: In a list of type VARCHAR, encountered a value of type LIST. Drill does not support lists of different types. .... SET the option 'exec.enable_union_type' to true and try again;
{noformat}
This behaviour is used for other error, example:
{noformat}
...
Error: UNSUPPORTED_OPERATION ERROR: This query cannot be planned possibly due to either a cartesian join or an inequality join. 
If a cartesian or inequality join is used intentionally, set the option 'planner.enable_nljoin_for_scalar_only' to false and try again.
{noformat}



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