private static DBAggregationConfigurationMapper loadDBAggregationConfigurationMapper()
            throws CannotLoadConfigurationException {
        if (mapper == null) {
            synchronized (DBAggregationQueryUtil.class) {
                DBAggregationQueryConfiguration config = loadQueryConfiguration();
                mapper = new DBAggregationConfigurationMapper(config);
            }
        }
        return mapper;
    }
Checks and returns an instance of the RDBMS query configuration mapper.

@return an instance of {@link DBAggregationConfigurationMapper}.
@throws CannotLoadConfigurationException if the configuration cannot be loaded.
modules/siddhi-core/src/main/java/io/siddhi/core/aggregation/persistedaggregation/config/DBAggregationQueryUtil.java