code: public static void initializeDatabase(String username, String defaultCatalogName, String defaultSchemaName,
                                            Database database) throws DatabaseException {
          if (((defaultCatalogName != null) || (defaultSchemaName != null)) && !(database.getConnection() instanceof
              OfflineConnection)) {
              if (database instanceof OracleDatabase) {
                  String schema = defaultCatalogName;
                  if (schema == null) {
                      schema = defaultSchemaName;
                  }
                  ExecutorService.getInstance().getExecutor(database).execute(
                      new RawSqlStatement("ALTER SESSION SET CURRENT_SCHEMA=" +
                          database.escapeObjectName(schema, Schema.class)));
              } else if (database instanceof PostgresDatabase && defaultSchemaName != null) {
                      ExecutorService.getInstance().getExecutor(database).execute(new RawSqlStatement("SET SEARCH_PATH TO " + database.escapeObjectName(defaultSchemaName, Schema.class)));
              } else if (database instanceof AbstractDb2Database) {
                  String schema = defaultCatalogName;
                  if (schema == null) {
                      schema = defaultSchemaName;
                  }
                  ExecutorService.getInstance().getExecutor(database).execute(new RawSqlStatement("SET CURRENT SCHEMA "
                          + schema));
              } else if (database instanceof MySQLDatabase) {
                  String schema = defaultCatalogName;
                  if (schema == null) {
                      schema = defaultSchemaName;
                  }
                  ExecutorService.getInstance().getExecutor(database).execute(new RawSqlStatement("USE " + schema));
              }
  
          }
      }
docs: Executes RawSqlStatements particular to each database engine to set the default schema for the given Database
  
  @param username           The username used for the connection. Used with MSSQL databases
  @param defaultCatalogName Catalog name and schema name are similar concepts.
  Used if defaultCatalogName is null.
  @param defaultSchemaName  Catalog name and schema name are similar concepts.
  Catalog is used with Oracle, DB2 and MySQL, and takes
  precedence over the schema name.
  @param database           Which Database object is affected by the initialization.
  @throws DatabaseException