Add unused algorithm finder for readwrite-splitting (#33656)

* Add unused algorithm finder for readwrite-splitting

* Remove useless TODO comment

features/readwrite-splitting/distsql/handler/src/main/java/org/apache/shardingsphere/readwritesplitting/distsql/handler/update/AlterReadwriteSplittingRuleExecutor.java

@@ -23,18 +23,15 @@
 import org.apache.shardingsphere.infra.algorithm.core.config.AlgorithmConfiguration;
 import org.apache.shardingsphere.infra.metadata.database.ShardingSphereDatabase;
 import org.apache.shardingsphere.readwritesplitting.config.ReadwriteSplittingRuleConfiguration;
-import org.apache.shardingsphere.readwritesplitting.config.rule.ReadwriteSplittingDataSourceGroupRuleConfiguration;
 import org.apache.shardingsphere.readwritesplitting.distsql.handler.checker.ReadwriteSplittingRuleStatementChecker;
 import org.apache.shardingsphere.readwritesplitting.distsql.handler.converter.ReadwriteSplittingRuleStatementConverter;
 import org.apache.shardingsphere.readwritesplitting.distsql.statement.AlterReadwriteSplittingRuleStatement;
 import org.apache.shardingsphere.readwritesplitting.rule.ReadwriteSplittingRule;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
-import java.util.LinkedList;
-import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
 
 /**
  * Alter readwrite-splitting rule executor.
@@ -59,16 +56,10 @@ public ReadwriteSplittingRuleConfiguration buildToBeAlteredRuleConfiguration(fin
 
     @Override
     public ReadwriteSplittingRuleConfiguration buildToBeDroppedRuleConfiguration(final ReadwriteSplittingRuleConfiguration toBeAlteredRuleConfig) {
-        Collection<ReadwriteSplittingDataSourceGroupRuleConfiguration> dataSourceGroups = new LinkedList<>();
-        Map<String, AlgorithmConfiguration> loadBalancers = new HashMap<>(rule.getConfiguration().getDataSourceGroups().size(), 1F);
-        List<String> toBeAlteredDataSourceNames = toBeAlteredRuleConfig.getDataSourceGroups().stream().map(ReadwriteSplittingDataSourceGroupRuleConfiguration::getName).collect(Collectors.toList());
-        for (ReadwriteSplittingDataSourceGroupRuleConfiguration each : rule.getConfiguration().getDataSourceGroups()) {
-            if (toBeAlteredDataSourceNames.contains(each.getName())) {
-                dataSourceGroups.add(each);
-                loadBalancers.put(each.getLoadBalancerName(), rule.getConfiguration().getLoadBalancers().get(each.getLoadBalancerName()));
-            }
-        }
-        return new ReadwriteSplittingRuleConfiguration(dataSourceGroups, loadBalancers);
+        Collection<String> unusedLoadBalancers = UnusedAlgorithmFinder.findUnusedLoadBalancers(rule.getConfiguration());
+        Map<String, AlgorithmConfiguration> toBeDroppedLoadBalancers = new HashMap<>(unusedLoadBalancers.size(), 1F);
+        unusedLoadBalancers.forEach(each -> toBeDroppedLoadBalancers.put(each, rule.getConfiguration().getLoadBalancers().get(each)));
+        return new ReadwriteSplittingRuleConfiguration(Collections.emptyList(), toBeDroppedLoadBalancers);
     }
 
     @Override

features/readwrite-splitting/distsql/handler/src/main/java/org/apache/shardingsphere/readwritesplitting/distsql/handler/update/UnusedAlgorithmFinder.java

@@ -0,0 +1,45 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.shardingsphere.readwritesplitting.distsql.handler.update;
+
+import lombok.AccessLevel;
+import lombok.NoArgsConstructor;
+import org.apache.shardingsphere.readwritesplitting.config.ReadwriteSplittingRuleConfiguration;
+import org.apache.shardingsphere.readwritesplitting.config.rule.ReadwriteSplittingDataSourceGroupRuleConfiguration;
+
+import java.util.Collection;
+import java.util.stream.Collectors;
+
+/**
+ * Unused algorithm finder.
+ */
+@NoArgsConstructor(access = AccessLevel.PRIVATE)
+public final class UnusedAlgorithmFinder {
+
+    /**
+     * Find unused load balancers.
+     *
+     * @param ruleConfig readwrite-splitting rule configuration
+     * @return found unused load balancers
+     */
+    public static Collection<String> findUnusedLoadBalancers(final ReadwriteSplittingRuleConfiguration ruleConfig) {
+        Collection<String> inUsedLoadBalancers = ruleConfig.getDataSourceGroups().stream().map(ReadwriteSplittingDataSourceGroupRuleConfiguration::getLoadBalancerName)
+                .collect(Collectors.toSet());
+        return ruleConfig.getLoadBalancers().keySet().stream().filter(each -> !inUsedLoadBalancers.contains(each)).collect(Collectors.toSet());
+    }
+}

infra/distsql-handler/src/main/java/org/apache/shardingsphere/distsql/handler/engine/update/rdl/rule/engine/database/type/AlterDatabaseRuleOperator.java

@@ -49,9 +49,9 @@ public final class AlterDatabaseRuleOperator implements DatabaseRuleOperator {
     public void operate(final DatabaseRuleDefinitionStatement sqlStatement, final ShardingSphereDatabase database, final RuleConfiguration currentRuleConfig) throws SQLException {
         RuleConfiguration toBeAlteredRuleConfig = executor.buildToBeAlteredRuleConfiguration(sqlStatement);
         MetaDataManagerPersistService metaDataManagerPersistService = contextManager.getPersistServiceFacade().getMetaDataManagerPersistService();
+        metaDataManagerPersistService.alterRuleConfiguration(database.getName(), decorateRuleConfiguration(database, toBeAlteredRuleConfig));
         RuleConfiguration toBeDroppedRuleConfig = executor.buildToBeDroppedRuleConfiguration(toBeAlteredRuleConfig);
         metaDataManagerPersistService.removeRuleConfigurationItem(database.getName(), toBeDroppedRuleConfig);
-        metaDataManagerPersistService.alterRuleConfiguration(database.getName(), decorateRuleConfiguration(database, toBeAlteredRuleConfig));
     }
 
     @SuppressWarnings("unchecked")

infra/distsql-handler/src/main/java/org/apache/shardingsphere/distsql/handler/engine/update/rdl/rule/spi/database/DatabaseRuleAlterExecutor.java

@@ -39,7 +39,6 @@ public interface DatabaseRuleAlterExecutor<T extends SQLStatement, R extends Sha
     C buildToBeAlteredRuleConfiguration(T sqlStatement);
 
     /**
-     * TODO Remove temporary default implementation
      * Build to be dropped rule configuration.
      *
      * @param toBeAlteredRuleConfig new rule configuration to be renewed