129 lines
3.7 KiB
PL/PgSQL
129 lines
3.7 KiB
PL/PgSQL
-- =====================================================
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-- Atomic Booking Creation with Overlap Prevention
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--
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-- Problem: Creating a booking requires checking room
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-- availability, validating capacity, and inserting — all
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-- as separate queries. Race conditions can double-book
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-- a room for overlapping dates.
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--
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-- Fix:
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-- A) Enable btree_gist extension for exclusion constraints.
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-- B) Add GiST exclusion constraint to prevent overlapping
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-- bookings for the same room (non-cancelled/no_show).
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-- C) Single transactional PG function that locks the room,
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-- validates inputs, calculates price, and inserts. The
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-- exclusion constraint provides a final safety net.
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-- =====================================================
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-- A) Enable btree_gist extension (required for exclusion constraints on non-GiST types)
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CREATE EXTENSION IF NOT EXISTS btree_gist;
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-- B) Add exclusion constraint to prevent overlapping bookings (idempotent)
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DO $$
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BEGIN
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IF NOT EXISTS (
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SELECT 1 FROM pg_constraint WHERE conname = 'excl_booking_room_dates'
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) THEN
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ALTER TABLE public.bookings
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ADD CONSTRAINT excl_booking_room_dates
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EXCLUDE USING gist (
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room_id WITH =,
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daterange(check_in, check_out) WITH &&
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) WHERE (status NOT IN ('cancelled', 'no_show'));
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END IF;
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END;
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$$;
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-- C) Atomic booking creation function
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CREATE OR REPLACE FUNCTION public.create_booking_atomic(
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p_account_id uuid,
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p_room_id uuid,
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p_guest_id uuid DEFAULT NULL,
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p_check_in date DEFAULT NULL,
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p_check_out date DEFAULT NULL,
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p_adults integer DEFAULT 1,
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p_children integer DEFAULT 0,
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p_status text DEFAULT 'confirmed',
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p_total_price numeric DEFAULT NULL,
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p_notes text DEFAULT NULL
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)
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RETURNS uuid
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LANGUAGE plpgsql
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SECURITY DEFINER
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SET search_path = ''
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AS $$
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DECLARE
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v_room record;
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v_computed_price numeric(10,2);
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v_booking_id uuid;
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BEGIN
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-- 1. Lock the room row to serialize booking attempts
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SELECT * INTO v_room
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FROM public.rooms
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WHERE id = p_room_id
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FOR UPDATE;
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-- 2. Validate room exists
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IF v_room IS NULL THEN
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RAISE EXCEPTION 'Room % not found', p_room_id
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USING ERRCODE = 'P0002';
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END IF;
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-- 3. Validate check_out > check_in
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IF p_check_in IS NULL OR p_check_out IS NULL THEN
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RAISE EXCEPTION 'check_in and check_out dates are required'
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USING ERRCODE = 'P0001';
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END IF;
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IF p_check_out <= p_check_in THEN
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RAISE EXCEPTION 'check_out (%) must be after check_in (%)', p_check_out, p_check_in
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USING ERRCODE = 'P0001';
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END IF;
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-- 4. Validate total guests do not exceed room capacity
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IF (p_adults + p_children) > v_room.capacity THEN
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RAISE EXCEPTION 'Total guests (%) exceed room capacity (%)', (p_adults + p_children), v_room.capacity
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USING ERRCODE = 'P0001';
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END IF;
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-- 5. Calculate price if not provided
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IF p_total_price IS NOT NULL THEN
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v_computed_price := p_total_price;
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ELSE
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v_computed_price := v_room.price_per_night * (p_check_out - p_check_in);
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END IF;
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-- 6. Insert the booking (exclusion constraint prevents double-booking)
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INSERT INTO public.bookings (
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account_id,
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room_id,
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guest_id,
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check_in,
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check_out,
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adults,
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children,
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status,
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total_price,
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notes
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) VALUES (
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p_account_id,
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p_room_id,
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p_guest_id,
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p_check_in,
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p_check_out,
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p_adults,
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p_children,
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p_status,
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v_computed_price,
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p_notes
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)
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RETURNING id INTO v_booking_id;
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-- 7. Return the new booking id
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RETURN v_booking_id;
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END;
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$$;
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GRANT EXECUTE ON FUNCTION public.create_booking_atomic(uuid, uuid, uuid, date, date, integer, integer, text, numeric, text) TO authenticated;
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GRANT EXECUTE ON FUNCTION public.create_booking_atomic(uuid, uuid, uuid, date, date, integer, integer, text, numeric, text) TO service_role;
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