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https://issues.apache.org/jira/browse/HIVE-26135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17521205#comment-17521205
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Zoltan Haindrich commented on HIVE-26135:
-----------------------------------------
wanted to add a check for "Strong"-ness; however, consider:
{code}
(leftCol + rightCol) IS NULL
{code}
since we want to deduce that the nullness of the expression strongly depends on
that `rightCol` can not be anything else than `null`... like:
{code}
(a + null) IS NULL
{code}
however; if the lefthandside is null - could also make it null; and in case
rightCol is not in the joinkeys we could loose correct results...
> Invalid Anti join conversion may cause missing results
> ------------------------------------------------------
>
> Key: HIVE-26135
> URL: https://issues.apache.org/jira/browse/HIVE-26135
> Project: Hive
> Issue Type: Bug
> Reporter: Zoltan Haindrich
> Assignee: Zoltan Haindrich
> Priority: Major
>
> right now I think the following is needed to trigger the issue:
> * left outer join
> * only select left hand side columns
> * conditional which is using some udf
> * the nullness of the udf is checked
> repro sql; in case the conversion happens the row with 'a' will be missing
> {code}
> drop table if exists t;
> drop table if exists n;
> create table t(a string) stored as orc;
> create table n(a string) stored as orc;
> insert into t values ('a'),('1'),('2'),(null);
> insert into n values ('a'),('b'),('1'),('3'),(null);
> explain select n.* from n left outer join t on (n.a=t.a) where
> assert_true(t.a is null) is null;
> explain select n.* from n left outer join t on (n.a=t.a) where cast(t.a as
> float) is null;
> select n.* from n left outer join t on (n.a=t.a) where cast(t.a as float) is
> null;
> set hive.auto.convert.anti.join=false;
> select n.* from n left outer join t on (n.a=t.a) where cast(t.a as float) is
> null;
> {code}
> workaround could be to disable the feature:
> {code}
> set hive.auto.convert.anti.join=false;
> {code}
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