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  1. Calcite
  2. CALCITE-4170

Improve simplification of "<>" predicates

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Details

    • Bug
    • Status: Closed
    • Major
    • Resolution: Fixed
    • None
    • 1.26.0
    • None
    • None

    Description

      Improve simplification of "<>" (not equals) predicates. The goal is to simplify "a <> 1 or a = 1" to "true".

      Today we can simplify "a = 1 or a <> 1" to "true" (the same expression with the terms re-ordered) 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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            Unassigned Unassigned
            julianhyde Julian Hyde
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