Available in versions: Dev (3.20) | Latest (3.19) | 3.18

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


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

The COUNT(expression) aggregate function counts the number of non-NULL expression evaluations in the group. If the expression is a constant, then there are only two options:

  • The constant is NULL, in case of which the COUNT(NULL) value is always 0 (but that's not an aggregate function, so we're currently not replacing it yet)
  • The constant is anything else, in case of which the COUNT(const) value is always COUNT(*)

For clarity reasons, and in some RDBMS also for (slight) performance reasons, COUNT(*) should be preferred.

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

-- With Settings.transformPatternsCountConstant active, this:

-- ... is transformed into the equivalent expression:
  COUNT(NULL), -- Might be replaced by 0 in the future, if other aggregates are present

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