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https://issues.apache.org/jira/browse/DRILL-6146?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Khurram Faraaz updated DRILL-6146:
----------------------------------
Affects Version/s: 1.14.0
> UNION with empty input on any one side returns incorrect results
> ----------------------------------------------------------------
>
> Key: DRILL-6146
> URL: https://issues.apache.org/jira/browse/DRILL-6146
> Project: Apache Drill
> Issue Type: Bug
> Components: Query Planning & Optimization
> Affects Versions: 1.12.0, 1.14.0
> Reporter: Khurram Faraaz
> Assignee: Vitalii Diravka
> Priority: Critical
>
> When any one side of the UNION has an empty file as input, Drill returns
> incorrect results.
>
> table t3 does not have any data inserted into its rows. Postgress returns 1
> as the result for both the queries, whereas Drill does not.
>
> {noformat}
> postgres=# create table t3(id int, name varchar(25));
> CREATE TABLE
> postgres=# select * from (values(1)) t union select id from t3;
> 1
>
> postgres=# select id from t3 union select * from (values(1)) t;
> 1
> {noformat}
>
>
> Results from Drill 1.12.0-mapr, note we return result 1 as result after the
> union.
> We have a directory named empty_JSON_f , and it has a single empty JSON file
> (that JSON file has no content in it, it is empty).
>
> {noformat}
> 0: jdbc:drill:schema=dfs.tmp> select * from (values(1)) UNION select id from
> empty_JSON_f;
> +---------+
> | EXPR$0 |
> +---------+
> | 1 |
> +---------+
> 1 row selected (2.272 seconds){noformat}
> However, in this query we return null and loose the value 1 from the right
> hand side, after the union, this doesn't seem correct
> {noformat}
> 0: jdbc:drill:schema=dfs.tmp> select id from empty_JSON_f UNION select * from
> (values(1));
> +-------+
> | id |
> +-------+
> | null |
> +-------+
> 1 row selected (0.33 seconds){noformat}
>
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