docs: private Catalog compileCatalogInternal(
              final VoltCompilerReader cannonicalDDLIfAny,
              final Catalog previousCatalogIfAny,
              final List<VoltCompilerReader> ddlReaderList,
              final InMemoryJarfile jarOutput)
      {
          m_catalog = new Catalog();
          // Initialize the catalog for one cluster
          m_catalog.execute("add / clusters cluster");
          m_catalog.getClusters().get("cluster").setSecurityenabled(false);
  
          // shutdown and make a new hsqldb
          try {
              Database previousDBIfAny = null;
              if (previousCatalogIfAny != null) {
                  previousDBIfAny = previousCatalogIfAny.getClusters().get("cluster").getDatabases().get("database");
              }
              compileDatabaseNode(cannonicalDDLIfAny, previousDBIfAny, ddlReaderList, jarOutput);
          } catch (final VoltCompilerException e) {
              return null;
          }
  
          assert(m_catalog != null);
  
          // add epoch info to catalog
          final int epoch = (int)(TransactionIdManager.getEpoch() / 1000);
          m_catalog.getClusters().get("cluster").setLocalepoch(epoch);
  
          return m_catalog;
      }