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https://issues.apache.org/jira/browse/DRILL-2328?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Hsuan-Yi Chu updated DRILL-2328:
-------------------------------------
Assignee: Aman Sinha (was: Sean Hsuan-Yi Chu)
> Concat operator returns wrong result when one of the operands is NULL
> ---------------------------------------------------------------------
>
> Key: DRILL-2328
> URL: https://issues.apache.org/jira/browse/DRILL-2328
> Project: Apache Drill
> Issue Type: Bug
> Components: Query Planning & Optimization
> Affects Versions: 0.8.0
> Reporter: Victoria Markman
> Assignee: Aman Sinha
> Priority: Critical
> Attachments: DRILL-2328.1.patch
>
>
> Queries below should return NULL:
> {code}
> 0: jdbc:drill:schema=dfs> select cast(null as varchar(10)) || '--' from t1;
> +------------+
> | EXPR$0 |
> +------------+
> | -- |
> | -- |
> | -- |
> | -- |
> | -- |
> | -- |
> | -- |
> | -- |
> | -- |
> | -- |
> +------------+
> 10 rows selected (0.09 seconds)
> 0: jdbc:drill:schema=dfs> select a1 || '--' from t1 where a1 is null;
> +------------+
> | EXPR$0 |
> +------------+
> | -- |
> +------------+
> 1 row selected (0.105 seconds)
> {code}
> Looks harmless at first, but a very common pattern in many customer queries
> will be broken: grouping by using '||' as following:
> {code}
> select
> cast(extract(day from c_timestamp) as varchar(10)) || '-' ||
> cast(extract(month from c_timestamp) as varchar(10)) || '-' ||
> cast(extract(year from c_timestamp) as varchar(10)),
> sum(c_integer) as sum1
> from
> alltypes_with_nulls
> group by
> cast(extract(day from c_timestamp) as varchar(10)) || '-' ||
> cast(extract(month from c_timestamp) as varchar(10)) || '-' ||
> cast(extract(year from c_timestamp) as varchar(10))
> order by
> cast(extract(day from c_timestamp) as varchar(10)) || '-' ||
> cast(extract(month from c_timestamp) as varchar(10)) || '-' ||
> cast(extract(year from c_timestamp) as varchar(10))
> ;
> {code}
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