No Postgres _like index when unique=True

[dylan@…]

class Species(models.Model):
    scientific_name = models.CharField(max_length=200, db_index=True)

Generates 2 indexes:

BEGIN;
CREATE INDEX "species_species_scientific_name" ON "species_species" ("scientific_name");
CREATE INDEX "species_species_scientific_name_like" ON "species_species" ("scientific_name" varchar_pattern_ops);

COMMIT;

class Species(models.Model):
    scientific_name = models.CharField(max_length=200, unique=True, db_index=True)

...does not create any indexes, because it depends on UNIQUE, but it SHOULD generate the index:

CREATE INDEX "species_species_scientific_name_like" ON "species_species" ("scientific_name" varchar_pattern_ops);

to make sure Postgres is optimized for LIKE operator.