private String namespaceToDatabase(String[] namespace) {
    Preconditions.checkArgument(namespace.length == 1, "only support namespace with 1 level.");
    return namespace[0];
  }
Unified catalog implement for spark engine.
amoro-format-mixed/amoro-mixed-spark/amoro-mixed-spark-3-common/src/main/java/org/apache/amoro/spark/SparkUnifiedCatalogBase.java