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1   /*
2    * Copyright (c) 2010.  The Apache Software Foundation
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *     http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing, software
15   * distributed under the License is distributed on an "AS IS" BASIS,
16   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17   * See the License for the specific language governing permissions and
18   * limitations under the License.
19   */
20  
21  package org.apache.hadoop.hbase.hbql.statement;
22  
23  import org.apache.hadoop.hbase.hbql.client.ExecutionResults;
24  import org.apache.hadoop.hbase.hbql.client.HBqlException;
25  import org.apache.hadoop.hbase.hbql.impl.HConnectionImpl;
26  import org.apache.hadoop.hbase.hbql.mapping.TableMapping;
27  
28  public class DescribeMappingStatement extends StatementWithMapping implements ConnectionStatement {
29  
30      public DescribeMappingStatement(final String mappingName) {
31          super(null, mappingName);
32      }
33  
34      protected ExecutionResults execute(final HConnectionImpl conn) throws HBqlException {
35  
36          this.getMappingContext().validateMappingName(conn);
37  
38          final TableMapping tableMapping = this.getMappingContext().getTableMapping();
39  
40          if (tableMapping == null)
41              return new ExecutionResults("Unknown mapping: " + this.getMappingContext().getMappingName());
42          else
43              return new ExecutionResults(tableMapping.asString());
44      }
45  
46      public static String usage() {
47          return "DESCRIBE MAPPING mapping_name";
48      }
49  }