-- AP1.5d: Rekursive Tasks unter Action

ALTER TABLE tasks
    ADD COLUMN IF NOT EXISTS parent_task_id UUID NULL
        REFERENCES tasks (id) ON DELETE CASCADE;

CREATE INDEX IF NOT EXISTS idx_tasks_parent
    ON tasks (tenant_id, parent_task_id)
    WHERE parent_task_id IS NOT NULL;

CREATE INDEX IF NOT EXISTS idx_tasks_action_parent
    ON tasks (tenant_id, action_id, parent_task_id);