Get Task Runs Graph Data

Per-day cost + runtime time series for ONE Snowflake task (the cost graph on the task-detail drill-down). Scoped to the qualified (database_name, schema_name, name) identity, summed across every warehouse the task ran on, read from snowflake_tasks_aggregated. start_date / end_date are optional (the UI date picker): when supplied the series is limited to that range; when omitted it covers the task's full retained history. Warehouse RBAC is enforced inline (the rollup carries warehouse_name).