Moheeb Zara
705f03a299
Deferred deeper-audit P1. signUpForClass (count->decide->insert) and cancelMySignup (cancel->recount->promote) were non-atomic: concurrent signups at the capacity boundary over-enrolled and concurrent cancels double-promoted waitlisters (dynamic capacity can't be a DB constraint). Migration 045 adds class_signup_tx/class_cancel_tx (SECURITY DEFINER, pg_advisory_xact_lock per session) doing the decision+write atomically; actions call the RPCs and keep all pre-checks. Removed the now-unused effectiveCapacity/computeSignupStatus/pickPromotion imports + isUniqueViolation (pure rules still live + tested in classes-logic). 528 tests; build clean.
96 lines
3.8 KiB
PL/PgSQL
96 lines
3.8 KiB
PL/PgSQL
-- =============================================================================
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-- 045: Class signup/cancel concurrency (P1, deeper-audit deferred)
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-- =============================================================================
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-- signUpForClass did count-registered -> decide -> insert and cancelMySignup
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-- did cancel -> recount -> promote, both non-atomic: concurrent signups at
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-- the capacity boundary over-enrolled, and concurrent cancels double-promoted
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-- waitlisters. Capacity is dynamic (session OR class), so a constraint can't
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-- express it. These functions serialize all signup/cancel for a session with
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-- a per-session advisory xact lock and do the decision + write atomically.
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--
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-- The pure lib/classes-logic.ts (computeSignupStatus / pickPromotion) remains
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-- the documented rule and is unit-tested; the SQL below MUST match it and is
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-- the runtime authority. Idempotent: CREATE OR REPLACE.
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-- =============================================================================
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CREATE OR REPLACE FUNCTION public.class_signup_tx(
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p_session_id uuid, p_space_id uuid, p_member_id uuid
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) RETURNS TABLE(signup_id uuid, signup_status text, err text)
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LANGUAGE plpgsql SECURITY DEFINER SET search_path = public AS $$
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DECLARE
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v_cap int; v_reg int; v_status text; v_id uuid;
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BEGIN
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PERFORM pg_advisory_xact_lock(hashtext(p_session_id::text));
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IF EXISTS (
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SELECT 1 FROM class_signups
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WHERE session_id = p_session_id AND member_id = p_member_id
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AND space_id = p_space_id AND status <> 'cancelled'
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) THEN
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RETURN QUERY SELECT NULL::uuid, NULL::text, 'already'::text; RETURN;
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END IF;
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SELECT COALESCE(s.capacity, c.capacity) INTO v_cap
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FROM class_sessions s JOIN classes c ON c.id = s.class_id
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WHERE s.id = p_session_id AND s.space_id = p_space_id;
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IF NOT FOUND THEN
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RETURN QUERY SELECT NULL::uuid, NULL::text, 'no_session'::text; RETURN;
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END IF;
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SELECT count(*) INTO v_reg FROM class_signups
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WHERE session_id = p_session_id AND status = 'registered';
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v_status := CASE WHEN v_cap IS NULL OR v_reg < v_cap
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THEN 'registered' ELSE 'waitlisted' END;
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INSERT INTO class_signups (session_id, space_id, member_id, status)
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VALUES (p_session_id, p_space_id, p_member_id, v_status)
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RETURNING id INTO v_id;
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RETURN QUERY SELECT v_id, v_status, NULL::text;
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END;
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$$;
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CREATE OR REPLACE FUNCTION public.class_cancel_tx(
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p_session_id uuid, p_space_id uuid, p_member_id uuid
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) RETURNS TABLE(cancelled_id uuid, promoted_id uuid, err text)
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LANGUAGE plpgsql SECURITY DEFINER SET search_path = public AS $$
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DECLARE
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v_sid uuid; v_status text; v_cap int; v_reg int; v_prom uuid;
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BEGIN
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PERFORM pg_advisory_xact_lock(hashtext(p_session_id::text));
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SELECT id, status INTO v_sid, v_status FROM class_signups
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WHERE session_id = p_session_id AND member_id = p_member_id
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AND space_id = p_space_id AND status <> 'cancelled'
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LIMIT 1;
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IF NOT FOUND THEN
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RETURN QUERY SELECT NULL::uuid, NULL::uuid, 'not_signed_up'::text; RETURN;
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END IF;
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UPDATE class_signups SET status = 'cancelled' WHERE id = v_sid;
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v_prom := NULL;
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IF v_status = 'registered' THEN
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SELECT COALESCE(s.capacity, c.capacity) INTO v_cap
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FROM class_sessions s JOIN classes c ON c.id = s.class_id
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WHERE s.id = p_session_id AND s.space_id = p_space_id;
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SELECT count(*) INTO v_reg FROM class_signups
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WHERE session_id = p_session_id AND status = 'registered';
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IF v_cap IS NULL OR v_reg < v_cap THEN
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SELECT id INTO v_prom FROM class_signups
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WHERE session_id = p_session_id AND space_id = p_space_id
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AND status = 'waitlisted'
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ORDER BY signed_up_at ASC LIMIT 1;
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IF v_prom IS NOT NULL THEN
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UPDATE class_signups SET status = 'registered' WHERE id = v_prom;
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END IF;
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END IF;
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END IF;
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RETURN QUERY SELECT v_sid, v_prom, NULL::text;
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END;
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$$;
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