code: private long getStatementID(HsqlName schema, String sql) {
  
          LongValueHashMap sqlMap =
              (LongValueHashMap) schemaMap.get(schema.hashCode());
  
          if (sqlMap == null) {
              return -1;
          }
  
          return sqlMap.get(sql, -1);
      }
docs: Retrieves the registered compiled statement identifier associated with
  the specified SQL String, or a value less than zero, if no such
  statement has been registered.
  
  @param schema the schema id
  @param sql the SQL String
  @return the compiled statement identifier associated with the
  specified SQL String