PostgreSQL daterange not using index correctly

Question

I have a simple table which has a user_birthday field with a type of date (which can be NULL value)

CREATE TABLE users
(
  user_id bigserial NOT NULL,
  user         


        

Answer 1

BETWEEN includes upper and lower border. Your condition

WHERE user_birthday BETWEEN '1978-07-15'::date AND '1983-03-01'::date

matches

WHERE user_birthday <@ daterange('[1978-07-15,1983-03-01]')

I see you mention a btree index. For that use simple comparison operators.

Detailed manual page on which index is good for which operators.

The range type operators <@ or @> would work with GiST indexes.
Example:
Perform this hours of operation query in PostgreSQL