[CALCITE-935] Improve how ReduceExpressionsRule handles duplicate constraints

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.5.0
• Assignee: Pengcheng Xiong
• Reporter: Pengcheng Xiong
• Created: 23/Oct/15 23:15
• Updated: 10/Nov/15 08:02
• Resolved: 26/Oct/15 23:42

Description

We need to improve ReduceExpressionRule to deal with multiple "equals to literal" in predicate. In ReduceExpressionRule.java, L396-397:

final ImmutableMap<RexNode, RexLiteral> constants =
       predicateConstants(predicates);

The query is

select * from src where (key='12' and key is null);

Here 'key' is a string type and it is one of the columns of 'src' table.

Then we will have predicates

[=($0, '12'), isnull($0)]

which is the input of the
predicateConstants, and the function will return "{$0='12'}"