-- A/B test event log. One row per exposure / cta_click / conversion.
-- Kept narrow on purpose: the goal is "did variant X get more conversions
-- than control" — not full session reconstruction.
create table if not exists ab_events (
  id bigserial primary key,
  experiment text not null,
  variant text not null,
  event_type text not null check (event_type in ('exposure', 'cta_click', 'conversion')),
  anon_id text not null,
  meta jsonb not null default '{}'::jsonb,
  created_at timestamptz not null default now()
);

create index if not exists ab_events_experiment_variant_idx
  on ab_events (experiment, variant, event_type, created_at desc);