110 lines
3.1 KiB
PL/PgSQL
110 lines
3.1 KiB
PL/PgSQL
-- =====================================================
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-- Atomic Course Enrollment
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--
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-- Problem: Enrolling a participant in a course requires
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-- multiple queries (check capacity, count enrolled, insert).
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-- Race conditions can over-enroll a course.
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--
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-- Fix: Single transactional PG function that locks the
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-- course row, validates capacity, and inserts with the
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-- correct status (enrolled vs waitlisted).
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-- =====================================================
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CREATE OR REPLACE FUNCTION public.enroll_course_participant(
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p_course_id uuid,
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p_member_id uuid DEFAULT NULL,
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p_first_name text DEFAULT NULL,
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p_last_name text DEFAULT NULL,
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p_email text DEFAULT NULL,
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p_phone text DEFAULT NULL
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)
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RETURNS jsonb
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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_course record;
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v_enrolled_count bigint;
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v_status public.enrollment_status;
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v_waitlist_position bigint;
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v_participant_id uuid;
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BEGIN
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-- 1. Lock the course row to prevent concurrent enrollment races
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SELECT * INTO v_course
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FROM public.courses
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WHERE id = p_course_id
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FOR UPDATE;
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IF v_course IS NULL THEN
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RAISE EXCEPTION 'Course % not found', p_course_id
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USING ERRCODE = 'P0002';
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END IF;
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-- 2. Validate course status is open for enrollment
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IF v_course.status != 'open' THEN
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RAISE EXCEPTION 'Course is not open for enrollment (current status: %)', v_course.status
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USING ERRCODE = 'P0001';
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END IF;
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-- 3. Check registration deadline hasn't passed
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IF v_course.registration_deadline IS NOT NULL AND v_course.registration_deadline < current_date THEN
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RAISE EXCEPTION 'Registration deadline (%) has passed', v_course.registration_deadline
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USING ERRCODE = 'P0001';
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END IF;
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-- 4. Count currently enrolled participants
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SELECT count(*) INTO v_enrolled_count
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FROM public.course_participants
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WHERE course_id = p_course_id
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AND status = 'enrolled';
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-- 5. Determine status based on capacity
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IF v_enrolled_count >= v_course.capacity THEN
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v_status := 'waitlisted';
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ELSE
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v_status := 'enrolled';
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END IF;
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-- 6. Insert the participant
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INSERT INTO public.course_participants (
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course_id,
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member_id,
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first_name,
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last_name,
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email,
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phone,
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status,
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enrolled_at
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) VALUES (
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p_course_id,
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p_member_id,
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p_first_name,
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p_last_name,
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p_email,
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p_phone,
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v_status,
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now()
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)
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RETURNING id INTO v_participant_id;
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-- 7. Calculate waitlist position if waitlisted
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IF v_status = 'waitlisted' THEN
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SELECT count(*) INTO v_waitlist_position
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FROM public.course_participants
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WHERE course_id = p_course_id
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AND status = 'waitlisted';
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END IF;
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-- 8. Return result
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RETURN jsonb_build_object(
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'participant_id', v_participant_id,
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'status', v_status::text,
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'waitlist_position', CASE WHEN v_status = 'waitlisted' THEN v_waitlist_position ELSE NULL END
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);
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END;
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$$;
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GRANT EXECUTE ON FUNCTION public.enroll_course_participant(uuid, uuid, text, text, text, text) TO authenticated;
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GRANT EXECUTE ON FUNCTION public.enroll_course_participant(uuid, uuid, text, text, text, text) TO service_role;
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