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From "Ruben Quesada Lopez (JIRA)" <>
Subject [jira] [Created] (CALCITE-2605) NullPointerException when left outer join implemented with EnumerableCorrelate
Date Wed, 03 Oct 2018 07:32:00 GMT
Ruben Quesada Lopez created CALCITE-2605:

             Summary: NullPointerException when left outer join implemented with EnumerableCorrelate
                 Key: CALCITE-2605
             Project: Calcite
          Issue Type: Bug
    Affects Versions: 1.17.0
            Reporter: Ruben Quesada Lopez
            Assignee: Julian Hyde
             Fix For: 1.18.0

In the context of a LEFT OUTER JOIN implemented via EnumerableCorrelate, the generated code
for the selector does not check if the right object is null (which can be, since it is a LEFT
join). This situation can lead to a NullPointerException.

The root cause is located in EnumerableCorrelate::implement method, which builds the selector
expression using a ternary operator whose "if" and "else" statements are switched:
    Expression selector =
            joinType.returnsJustFirstInput() ? joinType.toJoinType()
                : JoinRelType.INNER, physType,
            ImmutableList.of(leftResult.physType, rightResult.physType));
This code works (by coincidence) in the case of an INNER join; but in case of LEFT, it will incorrectly call EnumUtils.joinSelector(...)
with JoinRelType.INNER instead of JoinRelType.LEFT, which will produce the problematic generated
code. Also, the current code in the context of a SEMI or ANTI join will throw an IllegalStateException when
calling SemiJoinType::toJoinType.

If I am not mistaken, to fix this we just need to switch the ternary operator statements:
    Expression selector =
            joinType.returnsJustFirstInput() ? JoinRelType.INNER
                : joinType.toJoinType(), physType,
            ImmutableList.of(leftResult.physType, rightResult.physType));

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