create table if not exists public.usage_operations (
  id varchar(40) primary key,
  user_id varchar(40) not null references public.users(id) on delete cascade,
  operation varchar(48) not null,
  period_key varchar(16) not null,
  idempotency_key varchar(180) not null,
  status varchar(20) not null default 'reserved',
  units integer not null default 1 check (units > 0),
  request_id varchar(100),
  resource_id varchar(80),
  created_at timestamptz not null default now(),
  updated_at timestamptz not null default now(),
  completed_at timestamptz,
  constraint uq_usage_operations_user_operation_key
    unique (user_id, operation, idempotency_key),
  constraint ck_usage_operations_status
    check (status in ('reserved', 'completed', 'released'))
);

create index if not exists ix_usage_operations_user_period_operation
  on public.usage_operations(user_id, period_key, operation);

alter table public.usage_operations enable row level security;
revoke all on table public.usage_operations from anon, authenticated;