code: private String translateSchema(String schemaName) throws SQLException {
  
          if (useSchemaDefault && schemaName != null
                  && schemaName.length() == 0) {
              ResultSet rs = executeSelect("SYSTEM_SCHEMAS", "IS_DEFAULT=TRUE");
  
              if (rs.next()) {
                  return rs.getString(1);
              }
  
              return schemaName;
          }
  
          return schemaName;
      }
docs: For compatibility, when the connection property "default_schema=true"
  is present, any DatabaseMetaData call with an empty string as the
  schema parameter will use the default schema (noramlly "PUBLIC").