Range fields — the full lookups

# ======================================================================
# Range fields (`DateTimeRange`, `DateRange`, `IntegerRange`, `DecimalRange`)
# store an interval in one column. Lookups map to PostgreSQL range operators:
# `__overlap` (`&&`), `__adjacent_to` (`-|-`), `__fully_lt`/`__fully_gt`
# (`<<`/`>>`), `__contains` (`@>`), `__contained_by` (`<@`), plus bound
# transforms like `__startswith` (lower bound) and `__isempty`.
# ======================================================================

# ----------------------------------------------------------------------
# during overlaps [6/4, 6/7)
# ----------------------------------------------------------------------

# Django:
Reservation.objects.filter(during__overlap=Range(dt(2026,6,4), dt(2026,6,7)))

# SQL:
#   SELECT "examples_reservation"."id", "examples_reservation"."room", "examples_reservation"."during", "examples_reservation"."price_band", "examples_reservation"."date_span", "examples_reservation"."amount", "examples_reservation"."seq"
#   FROM "examples_reservation"
#   WHERE "examples_reservation"."during" && '["2026-06-04 00:00:00+00:00","2026-06-07 00:00:00+00:00")'::tstzrange

# Result:
#   room 101 [2026-06-01 00:00:00+00:00, 2026-06-05 00:00:00+00:00)
#   room 101 [2026-06-05 00:00:00+00:00, 2026-06-09 00:00:00+00:00)
#   room 202 [2026-06-02 00:00:00+00:00, 2026-06-06 00:00:00+00:00)

# ----------------------------------------------------------------------
# during adjacent to [6/9, 6/12)
# ----------------------------------------------------------------------

# Django:
Reservation.objects.filter(during__adjacent_to=Range(dt(2026,6,9), dt(2026,6,12)))

# SQL:
#   SELECT "examples_reservation"."id", "examples_reservation"."room", "examples_reservation"."during", "examples_reservation"."price_band", "examples_reservation"."date_span", "examples_reservation"."amount", "examples_reservation"."seq"
#   FROM "examples_reservation"
#   WHERE "examples_reservation"."during" -|- '["2026-06-09 00:00:00+00:00","2026-06-12 00:00:00+00:00")'::tstzrange

# Result:
#   room 101 [2026-06-05 00:00:00+00:00, 2026-06-09 00:00:00+00:00)

# ----------------------------------------------------------------------
# price_band fully below [300, 400)
# ----------------------------------------------------------------------

# Django:
Reservation.objects.filter(price_band__fully_lt=Range(300, 400))

# SQL:
#   SELECT "examples_reservation"."id", "examples_reservation"."room", "examples_reservation"."during", "examples_reservation"."price_band", "examples_reservation"."date_span", "examples_reservation"."amount", "examples_reservation"."seq"
#   FROM "examples_reservation"
#   WHERE "examples_reservation"."price_band" << '[300,400)'

# Result:
#   room 101 [2026-06-01 00:00:00+00:00, 2026-06-05 00:00:00+00:00)
#   room 101 [2026-06-05 00:00:00+00:00, 2026-06-09 00:00:00+00:00)
#   room 202 [2026-06-02 00:00:00+00:00, 2026-06-06 00:00:00+00:00)

# ----------------------------------------------------------------------
# price_band contains the value 175
# ----------------------------------------------------------------------

# Django:
Reservation.objects.filter(price_band__contains=175)

# SQL:
#   SELECT "examples_reservation"."id", "examples_reservation"."room", "examples_reservation"."during", "examples_reservation"."price_band", "examples_reservation"."date_span", "examples_reservation"."amount", "examples_reservation"."seq"
#   FROM "examples_reservation"
#   WHERE "examples_reservation"."price_band" @> (175)::integer

# Result:
#   room 101 [2026-06-01 00:00:00+00:00, 2026-06-05 00:00:00+00:00)
#   room 101 [2026-06-05 00:00:00+00:00, 2026-06-09 00:00:00+00:00)

# ----------------------------------------------------------------------
# amount range overlaps [190, 210)
# ----------------------------------------------------------------------

# Django:
Reservation.objects.filter(amount__overlap=Range(Decimal("190"), Decimal("210")))

# SQL:
#   SELECT "examples_reservation"."id", "examples_reservation"."room", "examples_reservation"."during", "examples_reservation"."price_band", "examples_reservation"."date_span", "examples_reservation"."amount", "examples_reservation"."seq"
#   FROM "examples_reservation"
#   WHERE "examples_reservation"."amount" && '[190,210)'::numrange

# Result:
#   room 101 [2026-06-01 00:00:00+00:00, 2026-06-05 00:00:00+00:00)
#   room 101 [2026-06-05 00:00:00+00:00, 2026-06-09 00:00:00+00:00)

# ----------------------------------------------------------------------
# date_span lower bound is 2026-06-01 (__startswith)
# ----------------------------------------------------------------------

# Django:
Reservation.objects.filter(date_span__startswith=date(2026, 6, 1))

# SQL:
#   SELECT "examples_reservation"."id", "examples_reservation"."room", "examples_reservation"."during", "examples_reservation"."price_band", "examples_reservation"."date_span", "examples_reservation"."amount", "examples_reservation"."seq"
#   FROM "examples_reservation"
#   WHERE lower("examples_reservation"."date_span") = '2026-06-01'::date

# Result:
#   room 101 [2026-06-01 00:00:00+00:00, 2026-06-05 00:00:00+00:00)

# ----------------------------------------------------------------------
# price_band is not empty (__isempty=False)
# ----------------------------------------------------------------------

# Django:
Reservation.objects.filter(price_band__isempty=False)

# SQL:
#   SELECT "examples_reservation"."id", "examples_reservation"."room", "examples_reservation"."during", "examples_reservation"."price_band", "examples_reservation"."date_span", "examples_reservation"."amount", "examples_reservation"."seq"
#   FROM "examples_reservation"
#   WHERE NOT isempty("examples_reservation"."price_band")

# Result:
#   room 101 [2026-06-01 00:00:00+00:00, 2026-06-05 00:00:00+00:00)
#   room 101 [2026-06-05 00:00:00+00:00, 2026-06-09 00:00:00+00:00)
#   room 202 [2026-06-02 00:00:00+00:00, 2026-06-06 00:00:00+00:00)