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https://issues.apache.org/jira/browse/DRILL-7195?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16824243#comment-16824243
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Aman Sinha commented on DRILL-7195:
-----------------------------------
[~vvysotskyi] regarding this issue, it is worth debating whether or not it
really is a blocker. The first scenario where no error is shown does not seem
like a blocker. The second case with wrong result occurs only when the
cast_empty_string_to_null is set to True, which is not the default setting.
Looking at the history of IS NULL simplification in Calcite, it is somewhat
complex issue and I feel that any fix we do could potentially introduce other
side effects which will prolong the release. Can we document this for 1.16 and
fix it in master ?
> Query returns incorrect result or does not fail when cast with is null is
> used in filter condition
> --------------------------------------------------------------------------------------------------
>
> Key: DRILL-7195
> URL: https://issues.apache.org/jira/browse/DRILL-7195
> Project: Apache Drill
> Issue Type: Bug
> Affects Versions: 1.16.0
> Reporter: Volodymyr Vysotskyi
> Assignee: Volodymyr Vysotskyi
> Priority: Blocker
> Fix For: 1.16.0
>
>
> 1. For the case when a query contains filter with a {{cast}} which cannot be
> done with {{is null}}, the query does not fail:
> {code:sql}
> select * from dfs.tmp.`a.json` as t where cast(t.a as integer) is null;
> +---+
> | a |
> +---+
> +---+
> No rows selected (0.142 seconds)
> {code}
> where
> {noformat}
> cat /tmp/a.json
> {"a":"aaa"}
> {noformat}
> But for the case when this condition is specified in project, query, as it is
> expected, fails:
> {code:sql}
> select cast(t.a as integer) is null from dfs.tmp.`a.json` t;
> Error: SYSTEM ERROR: NumberFormatException: aaa
> Fragment 0:0
> Please, refer to logs for more information.
> [Error Id: ed3982ce-a12f-4d63-bc6e-cafddf28cc24 on user515050-pc:31010]
> (state=,code=0)
> {code}
> This is a regression, for Drill 1.15 the first and the second queries are
> failed:
> {code:sql}
> select * from dfs.tmp.`a.json` as t where cast(t.a as integer) is null;
> Error: SYSTEM ERROR: NumberFormatException: aaa
> Fragment 0:0
> Please, refer to logs for more information.
> [Error Id: 2f878f15-ddaa-48cd-9dfb-45c04db39048 on user515050-pc:31010]
> (state=,code=0)
> {code}
> 2. For the case when {{drill.exec.functions.cast_empty_string_to_null}} is
> enabled, this issue will cause wrong results:
> {code:sql}
> alter system set `drill.exec.functions.cast_empty_string_to_null`=true;
> select * from dfs.tmp.`a1.json` t where cast(t.a as integer) is null;
> +---+
> | a |
> +---+
> +---+
> No rows selected (1.759 seconds)
> {code}
> where
> {noformat}
> cat /tmp/a1.json
> {"a":"1"}
> {"a":""}
> {noformat}
> Result for Drill 1.15.0:
> {code:sql}
> select * from dfs.tmp.`a1.json` t where cast(t.a as integer) is null;
> +----+
> | a |
> +----+
> | |
> +----+
> 1 row selected (1.724 seconds)
> {code}
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