-- Allocation is an external call, so a durable leased claim fences competing
-- allocator replicas before any provider request. A timed-out claim can be
-- recovered with the same deterministic allocation ID after a worker crash.
ALTER TABLE matches
    ADD COLUMN allocation_id TEXT UNIQUE,
    ADD COLUMN allocation_claimed_at TIMESTAMPTZ,
    ADD CONSTRAINT matches_allocation_claim_pair
        CHECK ((allocation_id IS NULL) = (allocation_claimed_at IS NULL));

CREATE INDEX matches_allocating_claimable
    ON matches (created_at, match_id)
    WHERE state = 'ALLOCATING' AND server_id IS NULL;