MySQL does too, yes, the comment is clearly incorrect: https://dev.mysql.com/doc/refman/8.0/en/is-null-optimization.html https://dev.mysql.com/doc/refman/8.0/en

MySQL does too, yes, the comment is clearly incorrect: https://dev.mysql.com/doc/refman/8.0/en/is-null-optimization.html https://dev.mysql.com/doc/refman/8.0/en/is-null-optimization... And it has done so for many versions, 8 is just the default redirect I got. The very first sentence on that page is: >MySQL can perform the same optimization on col_name IS NULL that it can use for col_name = constant_value. It works effectively everywhere, with the restriction that it can only do one null-optimized comparison per index (e.g. `(a == 1 or a is null) AND (b == 1 or b is null)` will only optimize one piece). Which is a potentially-significant restriction that makes me curious about the internals... but it does exist, and typical for MySQL is clearly documented.