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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