The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/11/static/indexes-unique.html
Description:
In https://www.postgresql.org/docs/11/static/indexes-unique.html there are
omited clausules
For example WHERE clausule is omited.
In https://www.postgresql.org/docs/11/static/sql-createindex.html you can
see the right sintax with all the clausules.