Available in versions: Dev (3.18) | Latest (3.17)

This is experimental functionality, and as such subject to change. Use at your own risk!

Merge NOT with DISTINCT predicate

Applies to ✅ Open Source Edition   ✅ Express Edition   ✅ Professional Edition   ✅ Enterprise Edition

The NOT predicate inverts its argument predicate. If the argument predicate is a DISTINCT predicate, we can simply merge the two operators to invert the argument into the inverse DISTINCT predicate.

Using Settings.transformPatternsNotNotDistinct, the following transformations can be achieved:

-- With Settings.transformPatternsNotNotDistinct active, this:
SELECT
  NOT (a IS NOT DISTINCT FROM b),
  NOT (a IS DISTINCT FROM b)
FROM tab;

-- ... is transformed into the equivalent expression:
SELECT 
  a IS DISTINCT FROM b,    -- NOT (a IS NOT DISTINCT FROM b)
  a IS NOT DISTINCT FROM b -- NOT (a IS DISTINCT FROM b)
FROM tab;

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