[CALCITE-2605] NullPointerException when left outer join implemented with EnumerableCorrelate

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.17.0
• Fix Version/s: 1.18.0
• Assignee: Julian Hyde
• Reporter: Ruben Q L
• Created: 03/Oct/18 07:31
• Updated: 23/Dec/18 00:12
• Resolved: 05/Nov/18 20:35

Description

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 =
        EnumUtils.joinSelector(
            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 =
        EnumUtils.joinSelector(
            joinType.returnsJustFirstInput() ? JoinRelType.INNER
                : joinType.toJoinType(), physType,
            ImmutableList.of(leftResult.physType, rightResult.physType));

 

Issue Links

• blocks: CALCITE-2575 Release Calcite 1.18.0
• blocks: CALCITE-2621 Add rule to execute semi joins with correlation
• links to: PR 901
• links to: PR#874