private void checkToBeReferencedShardingTablesExisted(final AlterShardingTableReferenceRuleStatement sqlStatement) {
        Collection<String> currentShardingTableNames = getCurrentShardingTableNames();
        Collection<String> notExistedTableNames = sqlStatement.getTableNames().stream().filter(each -> !currentShardingTableNames.contains(each)).collect(Collectors.toSet());
        ShardingSpherePreconditions.checkMustEmpty(notExistedTableNames, () -> new MissingRequiredRuleException("Sharding", database.getName(), notExistedTableNames));
    }
    
    private Collection<String> getCurrentShardingTableNames() {
        Collection<String> result = new CaseInsensitiveSet<>();
        result.addAll(rule.getConfiguration().getTables().stream().map(ShardingTableRuleConfiguration::getLogicTable).collect(Collectors.toSet()));
        result.addAll(rule.getConfiguration().getAutoTables().stream().map(ShardingAutoTableRuleConfiguration::getLogicTable).collect(Collectors.toSet()));
        return result;
    }
    
    private void checkShardingTableReferenceRulesValid(final AlterShardingTableReferenceRuleStatement sqlStatement) {

shardingRuleConfig.getShardingAlgorithms().put(result, createAlgorithmConfiguration(sqlStatement.getAlgorithmSegment()));
        return result;
    }
    
    private AlgorithmConfiguration createAlgorithmConfiguration(final AlgorithmSegment segment) {
        return new AlgorithmConfiguration(segment.getName(), segment.getProps());
    }
    
    private String getDefaultShardingAlgorithmName(final String defaultType, final String algorithmType) {
        return String.format("default_%s_%s", defaultType, algorithmType).toLowerCase();
    }
    
    private void setStrategyConfiguration(final ShardingRuleConfiguration ruleConfig, final String type, final ShardingStrategyConfiguration shardingStrategyConfig) {
        if (type.equalsIgnoreCase(ShardingStrategyLevelType.TABLE.name())) {
            ruleConfig.setDefaultTableShardingStrategy(shardingStrategyConfig);
        } else {
            ruleConfig.setDefaultDatabaseShardingStrategy(shardingStrategyConfig);
        }
    }
    
    @Override
    public ShardingRuleConfiguration buildToBeDroppedRuleConfiguration(final ShardingRuleConfiguration toBeAlteredRuleConfig) {

}
        UnusedAlgorithmFinder.findUnusedShardingAlgorithm(rule.getConfiguration()).forEach(each -> result.getShardingAlgorithms().put(each, rule.getConfiguration().getShardingAlgorithms().get(each)));
        UnusedAlgorithmFinder.findUnusedKeyGenerator(rule.getConfiguration()).forEach(each -> result.getKeyGenerators().put(each, rule.getConfiguration().getKeyGenerators().get(each)));
        UnusedAlgorithmFinder.findUnusedAuditor(rule.getConfiguration()).forEach(each -> result.getAuditors().put(each, rule.getConfiguration().getAuditors().get(each)));
        return result;
    }