Documentation discrepancy UNIQUE NULLS NOT DISTINCT

 From here:

https://www.postgresql.org/about/featurematrix/detail/392/

UNIQUE NULLS NOT DISTINCT

By default, NULL values are not treated as distinct entries. Specifying 
NULLS NOT DISTINCT on unique indexes / constraints will cause NULL 
values to be treated distinctly.


 From here:

https://www.postgresql.org/docs/current/sql-createindex.html

NULLS DISTINCT
NULLS NOT DISTINCT

     Specifies whether for a unique index, null values should be 
considered distinct (not equal). The default is that they are distinct, 
so that a unique index could contain multiple null values in a column.

and here:

https://www.postgresql.org/docs/current/sql-createtable.html

For the purpose of a unique constraint, null values are not considered 
equal, unless NULLS NOT DISTINCT is specified.

-- 
Adrian Klaver
adrian.klaver@aklaver.com