[jira] [Assigned] (DRILL-5667) Project operator would change output field order if convertfromJSON is used

["Jinfeng Ni (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DRILL-5667?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jinfeng Ni reassigned DRILL-5667:
---------------------------------

    Assignee: Jinfeng Ni

> Project operator would change output field order if convertfromJSON is used 
> ----------------------------------------------------------------------------
>
>                 Key: DRILL-5667
>                 URL: https://issues.apache.org/jira/browse/DRILL-5667
>             Project: Apache Drill
>          Issue Type: Bug
>            Reporter: Jinfeng Ni
>            Assignee: Jinfeng Ni
>
> When one of the projected expression uses convertfromJSON function, such expression would be put in the last of output fields.  In general, such rearrange of output fields would not cause problem, since most of Drill's execution operators uses name-based resolution. However, union/union-all operators uses positional reference. If one branch of union/union-all re-arranges the output fields, while the other branch does not, then it would lead either incorrect query result, or execution error.
> For instance, given the following json file:
> {code}
> a:  { b: 100, c : "DRILL"}}
> {code}
> The following query would fail with execution error:
> {code}
> select 'abc' as col1, convert_from(convert_to(t.a, 'JSON'), 'JSON') as col2, 'xyz' as col3 
> from dfs.tmp.`1.json` t 
> union all 
> select 'abc' as col1, t.a as col2, 'xyz' as col3 
> from dfs.tmp.`1.json` t;
> Error: SYSTEM ERROR: DrillRuntimeException: Type mismatch between VARCHAR on the left side and MAP on the right side in column 2 of UNION ALL
> {code}
> If we put the Map column as the last position in both of union all branches, the query will run successfully.
> {code}
> select 'abc' as col1, 'xyz' as col3, convert_from(convert_to(t.a, 'JSON'), 'JSON') as col2 
> from dfs.tmp.`1.json` t 
> union all 
> select 'abc' as col1, 'xyz' as col3, t.a as col2  
> from dfs.tmp.`1.json` t;
> +-------+-------+------------------------+
> | col1  | col3  |          col2          |
> +-------+-------+------------------------+
> | abc   | xyz   | {"b":100,"c":"DRILL"}  |
> | abc   | xyz   | {"b":100,"c":"DRILL"}  |
> +-------+-------+------------------------+
> {code}



--
This message was sent by Atlassian JIRA
(v6.4.14#64029)