That is a nice design. You can create a regular unique index where columns(s)s are not null and then filtered index(es) for the cases where some of the unique columns are null.
However my point, specifically, was that if the document in question would have offered alternative solutions, I personally would have been saved from some frustration and an exercise in bad index design (I had 5 nullables that need uniqueness for the null as well). Maybe it would help someone else.
On Fri, Sep 27, 2019 at 7:37 PM Bruce Momjian <bruce@momjian.us> wrote:
On Wed, Sep 4, 2019 at 01:12:35PM +0000, PG Doc comments form wrote: > The following documentation comment has been logged on the website: > > Page: https://www.postgresql.org/docs/11/indexes-unique.html > Description: > > Sometimes it is convenient to create an unique index that considers NULL > values equal. Designating a "zero" value for those rows might not be > feasible, for example due to a foreign key. > > The documentation currently only states that unique indexes do not consider > NULLs equal. It might be good to offer workarounds, like indexing a coalesce > function, if scans are not the reason for the index, but the uniqueness > constraint.
