CREATE TABLE worker_descriptors (
    descriptor_id TEXT PRIMARY KEY,
    attempt_id TEXT NOT NULL REFERENCES attempts (attempt_id) ON DELETE CASCADE,
    kind TEXT NOT NULL CHECK (kind IN ('resolved_source', 'checkpoint')),
    schema_version INTEGER NOT NULL CHECK (schema_version >= 1),
    payload JSONB NOT NULL,
    byte_length BIGINT NOT NULL CHECK (byte_length >= 0),
    item_count BIGINT CHECK (item_count >= 0),
    checksum TEXT NOT NULL,
    created_at TIMESTAMPTZ NOT NULL
);

CREATE INDEX worker_descriptors_attempt_idx
    ON worker_descriptors (attempt_id, kind, created_at, descriptor_id);