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   * 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,
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   * See the License for the specific language governing permissions and
   * limitations under the License.
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  package org.apache.cassandra.cql3.statements;
  
  import org.apache.cassandra.audit.AuditLogContext;
  import org.apache.cassandra.audit.AuditLogEntryType;
  import org.apache.cassandra.config.DatabaseDescriptor;
  import org.apache.cassandra.cql3.CQLStatement;
  import org.apache.cassandra.cql3.QueryOptions;
  import org.apache.cassandra.cql3.QueryProcessor;
  import org.apache.cassandra.exceptions.InvalidRequestException;
  import org.apache.cassandra.exceptions.UnauthorizedException;
  import org.apache.cassandra.transport.Dispatcher;
  import org.apache.cassandra.transport.messages.ResultMessage;
  import org.apache.cassandra.service.ClientState;
  import org.apache.cassandra.service.QueryState;
  import org.apache.commons.lang3.builder.ToStringBuilder;
  import org.apache.commons.lang3.builder.ToStringStyle;
  
  import static org.apache.cassandra.cql3.statements.RequestValidations.checkTrue;
  
  public class UseStatement extends CQLStatement.Raw implements CQLStatement
  {
      private final String keyspace;
  
      public UseStatement(String keyspace)
      {
          this.keyspace = keyspace;
      }
  
      public UseStatement prepare(ClientState state)
      {
          return this;
      }
  
      public void authorize(ClientState state) throws UnauthorizedException
      {
          state.validateLogin();
      }
  
      @Override
      public void validate(ClientState state) throws InvalidRequestException
      {
          checkTrue(DatabaseDescriptor.getUseStatementsEnabled(), "USE statements prohibited. (see use_statements_enabled in cassandra.yaml)");
      }
  
      @Override
      public ResultMessage execute(QueryState state, QueryOptions options, Dispatcher.RequestTime requestTime) throws InvalidRequestException
      {
          QueryProcessor.metrics.useStatementsExecuted.inc();
          state.getClientState().setKeyspace(keyspace);
          return new ResultMessage.SetKeyspace(keyspace);
      }
  
      public ResultMessage executeLocally(QueryState state, QueryOptions options) throws InvalidRequestException
      {
          // In production, internal queries are exclusively on the system keyspace and 'use' is thus useless
          // but for some unit tests we need to set the keyspace (e.g. for tests with DROP INDEX)
          return execute(state, options, Dispatcher.RequestTime.forImmediateExecution());
      }
      
      @Override
      public String toString()
      {
          return ToStringBuilder.reflectionToString(this, ToStringStyle.SHORT_PREFIX_STYLE);
      }
  
      @Override
      public AuditLogContext getAuditLogContext()
      {
          return new AuditLogContext(AuditLogEntryType.USE_KEYSPACE, keyspace);
      }
  
      public String keyspace()
      {
          return keyspace;
      }
  }
  