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https://issues.apache.org/jira/browse/DRILL-7426?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16961336#comment-16961336
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Paul Rogers commented on DRILL-7426:
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[~cgivre], I should have seen that one coming...
But, seriously, a provided schema turns out to be the best way to predict the
future.
> 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
> Priority: Trivial
>
> 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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