public boolean containsCustomRollUpMask(final CustomRollUpMask customRollUpMask) {
        if (customRollUpMasks != null) {
            return customRollUpMasks.contains(customRollUpMask);
        }
        return false;
    }
Cache the positions of the fields.
stroom-core-shared/src/main/java/stroom/statistics/impl/hbase/shared/StroomStatsStoreEntityData.java