[GitHub] [shardingsphere] taojintianxia commented on a change in pull request #10479: Show readwrite splitting & db discovery rules

[GitBox <gi...@apache.org>]

taojintianxia commented on a change in pull request #10479:
URL: https://github.com/apache/shardingsphere/pull/10479#discussion_r639462631



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File path: shardingsphere-proxy/shardingsphere-proxy-backend/src/main/java/org/apache/shardingsphere/proxy/backend/text/distsql/rql/impl/DatabaseDiscoveryRulesQueryBackendHandler.java
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@@ -0,0 +1,89 @@
+/*
+ * 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.proxy.backend.text.distsql.rql.impl;
+
+import com.google.common.collect.Maps;
+import org.apache.shardingsphere.dbdiscovery.api.config.DatabaseDiscoveryRuleConfiguration;
+import org.apache.shardingsphere.dbdiscovery.api.config.rule.DatabaseDiscoveryDataSourceRuleConfiguration;
+import org.apache.shardingsphere.distsql.parser.statement.rql.show.ShowDatabaseDiscoveryRulesStatement;
+import org.apache.shardingsphere.infra.config.algorithm.ShardingSphereAlgorithmConfiguration;
+import org.apache.shardingsphere.proxy.backend.communication.jdbc.connection.BackendConnection;
+import org.apache.shardingsphere.proxy.backend.context.ProxyContext;
+import org.apache.shardingsphere.proxy.backend.response.header.ResponseHeader;
+import org.apache.shardingsphere.proxy.backend.response.header.query.QueryResponseHeader;
+import org.apache.shardingsphere.proxy.backend.response.header.query.impl.QueryHeader;
+import org.apache.shardingsphere.proxy.backend.text.SchemaRequiredBackendHandler;
+
+import java.sql.Types;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+
+/**
+ * Backend handler for show database discovery rules.
+ */
+public final class DatabaseDiscoveryRulesQueryBackendHandler extends SchemaRequiredBackendHandler<ShowDatabaseDiscoveryRulesStatement> {
+
+    private Iterator<DatabaseDiscoveryDataSourceRuleConfiguration> data;
+
+    private Map<String, ShardingSphereAlgorithmConfiguration> discoverTypes;
+
+    public DatabaseDiscoveryRulesQueryBackendHandler(final ShowDatabaseDiscoveryRulesStatement sqlStatement, final BackendConnection backendConnection) {
+        super(sqlStatement, backendConnection);
+    }
+    
+    @Override
+    protected ResponseHeader execute(final String schemaName, final ShowDatabaseDiscoveryRulesStatement sqlStatement) {
+        loadRuleConfiguration(schemaName);
+        return new QueryResponseHeader(getQueryHeader(schemaName));
+    }
+    
+    private void loadRuleConfiguration(final String schemaName) {
+        Optional<DatabaseDiscoveryRuleConfiguration> ruleConfig = ProxyContext.getInstance().getMetaData(schemaName).getRuleMetaData().getConfigurations()
+                .stream().filter(each -> each instanceof DatabaseDiscoveryRuleConfiguration).map(each -> (DatabaseDiscoveryRuleConfiguration) each).findAny();
+        data = ruleConfig.map(optional -> optional.getDataSources().iterator()).orElse(Collections.emptyIterator());
+        discoverTypes = ruleConfig.map(DatabaseDiscoveryRuleConfiguration::getDiscoveryTypes).orElse(Maps.newHashMap());
+    }
+    
+    private List<QueryHeader> getQueryHeader(final String schemaName) {
+        List<QueryHeader> result = new LinkedList<>();
+        result.add(new QueryHeader(schemaName, "", "name", "name", Types.CHAR, "CHAR", 255, 0, false, false, false, false));

Review comment:
       I'm not quite familiar with the logic here, but the QueryHeader looks like magic number style. is that better if we define some constant QueryHeader like `public final QueryHeader XXX_QUERY_HEADER=new QueryHeader(schemaName, "", "name", "name", Types.CHAR, "CHAR", 255, 0, false, false, false, false)` ? or after 3 month , it's hard to understand the logic here even by yourself.




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