CREATE TABLE IF NOT EXISTS knowledge_deleted_cleanup_events (
    id                BIGSERIAL PRIMARY KEY,
    tenant_id          BIGINT NOT NULL,
    knowledge_item_id  BIGINT NOT NULL,
    status             VARCHAR(20) NOT NULL DEFAULT 'pending',
    attempt_count      INT NOT NULL DEFAULT 0,
    available_at       TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    locked_by          TEXT,
    locked_at          TIMESTAMPTZ,
    last_error         TEXT,
    completed_at       TIMESTAMPTZ,
    created_at         TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    updated_at         TIMESTAMPTZ NOT NULL DEFAULT NOW(),
    CHECK (status IN ('pending', 'processing', 'completed', 'failed')),
    CHECK (attempt_count >= 0)
);

CREATE UNIQUE INDEX IF NOT EXISTS uk_knowledge_deleted_cleanup_open
    ON knowledge_deleted_cleanup_events (tenant_id, knowledge_item_id)
    WHERE completed_at IS NULL;

CREATE INDEX IF NOT EXISTS idx_knowledge_deleted_cleanup_pending
    ON knowledge_deleted_cleanup_events (available_at, id)
    WHERE completed_at IS NULL AND status IN ('pending', 'failed');

CREATE INDEX IF NOT EXISTS idx_knowledge_deleted_cleanup_processing
    ON knowledge_deleted_cleanup_events (locked_at, id)
    WHERE completed_at IS NULL AND status = 'processing';