[jira] [Created] (CALCITE-4170) Improve simplification of "<>" predicates

["Julian Hyde (Jira)" <ji...@apache.org>]

Julian Hyde created CALCITE-4170:
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             Summary: Improve simplification of "<>" predicates
                 Key: CALCITE-4170
                 URL: https://issues.apache.org/jira/browse/CALCITE-4170
             Project: Calcite
          Issue Type: Bug
            Reporter: Julian Hyde


Improve simplification of "<>" (not equals) predicates.

Today we can simplify "a = 1 or a <> 1" to "true" but we cannot simplify "a <> 1 or a = 1" to "true". The problem is this. The algorithm for simplifying "or" builds a up a list of predicates as it works left to right. After dealing with "a = 1" RexSimplifier has a predicate "a = 1" and therefore it can simplify the next predicate to anything that returns the right result over the possible inputs - which will not include a = 1 - and therefore 'a <> 1' can be simplified to 'true'.

But today, we can't take that approach with "a <> 1 or a = 1" because "a <> 1" cannot be represented as a single range. It needs two ranges - less than 1 or greater than 1. The fix is therefore to allow predicates to be range sets not just ranges.



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