[GitHub] [shardingsphere] RaigorJiang commented on a change in pull request #12011: Support information_schema.schemata query

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

RaigorJiang commented on a change in pull request #12011:
URL: https://github.com/apache/shardingsphere/pull/12011#discussion_r696343285



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File path: shardingsphere-proxy/shardingsphere-proxy-backend/src/main/java/org/apache/shardingsphere/proxy/backend/text/admin/mysql/MySQLInformationSchemaExecutorFactory.java
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@@ -0,0 +1,47 @@
+/*
+ * 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.admin.mysql;
+
+import org.apache.shardingsphere.proxy.backend.text.admin.executor.DatabaseAdminQueryExecutor;
+import org.apache.shardingsphere.proxy.backend.text.admin.mysql.executor.information.SelectSchemataExecutor;
+import org.apache.shardingsphere.sql.parser.sql.common.segment.generic.table.SimpleTableSegment;
+import org.apache.shardingsphere.sql.parser.sql.common.statement.dml.SelectStatement;
+
+/**
+ * Construct the information schema executor's factory.
+ */
+public final class MySQLInformationSchemaExecutorFactory {
+    
+    public static final String SCHEMATA = "schemata";
+    
+    /**
+     * Create executor.
+     *
+     * @param sqlStatement SQL statement
+     * @param sql SQL being executed
+     * @return executor
+     */
+    public static DatabaseAdminQueryExecutor newInstance(final SelectStatement sqlStatement, final String sql) {
+        String tableName = ((SimpleTableSegment) sqlStatement.getFrom()).getTableName().getIdentifier().getValue();
+        if (SCHEMATA.equalsIgnoreCase(tableName)) {
+            return new SelectSchemataExecutor(sqlStatement, sql);
+        }
+        throw new UnsupportedOperationException("unsupported table");

Review comment:
       It is better to prompt the tableName in error message.
   Because `information_schema` is mostly queried automatically by SQL client, user does not know which table is being queried.




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