# Materialize v0.38
## v0.38.0

* Add `cpu_percent_normalized` to the `mz_internal.mz_{source,sink,cluster_replica}_utilization`
  system catalog views. This column provides an approximation of CPU utilization
  as a % of the total of compute workers.

* Add `mz_internal.mz_cluster_replica_frontiers`
  to the system catalog. This table describes the frontiers of each
  dataflow in the system.

* **Private preview.** Support the [`AS OF`](/sql/subscribe/#as-of) and [`UP TO`](/sql/subscribe/#up-to)
  clauses in `SUBSCRIBE`. These clauses allow specifying a timestamp at
  which `SUBSCRIBE` should begin returning results (`AS OF`), or cease
  running (`UP TO`).

  As is, all user-defined sources and tables have a retention window of one
  second, so `AS OF` is of limited use beyond subscribing to queries over
  specific system catalog objects (including `mz_cluster_replicas`,
  `mz_sources`, `mz_sinks`, `mz_internal.mz_cluster_replica_metrics`, and
  `mz_internal.mz_cluster_replica_sizes`).