private String inStorageDriver, outStorageDriver, tableName;

  @Override

  public ASTNode preAnalyze(HiveSemanticAnalyzerHookContext context, ASTNode ast)

  throws SemanticException {

    Hive db;

    try {

      db = context.getHive();

    } catch (HiveException e) {

      throw new SemanticException("Couldn't get Hive DB instance in semantic analysis phase.", e);

    }

    // Analyze and create tbl properties object

    int numCh = ast.getChildCount();

    String inputFormat = null, outputFormat = null;

    tableName = BaseSemanticAnalyzer.unescapeIdentifier(ast.getChild(0).getText());

    for (int num = 1; num < numCh; num++) {

      ASTNode child = (ASTNode) ast.getChild(num);

      switch (child.getToken().getType()) {

      case HiveParser.TOK_QUERY: // CTAS

        throw new SemanticException("Operation not supported. Create table as Select is not a valid operation.");

      case HiveParser.TOK_TABLEBUCKETS:

        throw new SemanticException("Operation not supported. Howl doesn't allow Clustered By in create table.");

      case HiveParser.TOK_TBLSEQUENCEFILE:

        throw new SemanticException("Operation not supported. Howl doesn't support Sequence File by default yet. " +

        "You may specify it through INPUT/OUTPUT storage drivers.");

      case HiveParser.TOK_TBLTEXTFILE:

        throw new SemanticException("Operation not supported. Howl doesn't support Text File by default yet. " +

        "You may specify it through INPUT/OUTPUT storage drivers.");

      case HiveParser.TOK_LIKETABLE:

        String likeTableName;

        if (child.getChildCount() > 0 && (likeTableName = BaseSemanticAnalyzer.unescapeIdentifier(child.getChild(0).getText())) != null) {

          throw new SemanticException("Operation not supported. CREATE TABLE LIKE is not supported.");

//          try {

//            tblProps = db.getTable(MetaStoreUtils.DEFAULT_DATABASE_NAME, likeTableName).getParameters();

//          } catch (HiveException he) {

//            throw new SemanticException(he);

//          }

//          if(!(tblProps.containsKey(InitializeInput.HOWL_ISD_CLASS) && tblProps.containsKey(InitializeInput.HOWL_OSD_CLASS))){

//            throw new SemanticException("Operation not supported. Table "+likeTableName+" should have been created through Howl. Seems like its not.");

//          }

//          return ast;

        }

        break;

      case HiveParser.TOK_IFNOTEXISTS:

        try {

          List<String> tables = db.getTablesByPattern(tableName);

          if (tables != null && tables.size() > 0) { // table exists

            return null;

          }

        } catch (HiveException e) {

          throw new SemanticException(e);

        }

        break;

      case HiveParser.TOK_TABLEPARTCOLS:

        List<FieldSchema> partCols = BaseSemanticAnalyzer.getColumns((ASTNode) child.getChild(0), false);

        for(FieldSchema fs : partCols){

          if(!fs.getType().equalsIgnoreCase("string")){

            throw new SemanticException("Operation not supported. Howl only supports partition columns of type string. " +

                "For column: "+fs.getName()+" Found type: "+fs.getType());

          }

        }

        break;

      case HiveParser.TOK_TABLEFILEFORMAT:

        if(child.getChildCount() < 4) {

          throw new SemanticException("Incomplete specification of File Format. You must provide InputFormat, OutputFormat, InputDriver, OutputDriver.");

        }

        inputFormat      = BaseSemanticAnalyzer.unescapeSQLString(child.getChild(0).getText());

        outputFormat     = BaseSemanticAnalyzer.unescapeSQLString(child.getChild(1).getText());

        inStorageDriver  = BaseSemanticAnalyzer.unescapeSQLString(child.getChild(2).getText());

        outStorageDriver = BaseSemanticAnalyzer.unescapeSQLString(child.getChild(3).getText());

        break;

      case HiveParser.TOK_TBLRCFILE:

        inputFormat      = RCFileInputFormat.class.getName();

        outputFormat     = RCFileOutputFormat.class.getName();

        inStorageDriver  = RCFileInputDriver.class.getName();

        outStorageDriver = RCFileOutputDriver.class.getName();

        break;

      }

    }

    if(inputFormat == null || outputFormat == null || inStorageDriver == null || outStorageDriver == null){

      throw new SemanticException("STORED AS specification is either incomplete or incorrect.");

    }

    return ast;

  }

  @Override

  public void postAnalyze(HiveSemanticAnalyzerHookContext context, List<Task<? extends Serializable>> rootTasks) throws SemanticException {

    if(rootTasks.size() == 0){

      // There will be no DDL task created in case if its CREATE TABLE IF NOT EXISTS

      return;

    }

    CreateTableDesc desc = ((DDLTask)rootTasks.get(rootTasks.size()-1)).getWork().getCreateTblDesc();

    // first check if we will allow the user to create table.

    authorize(context, desc.getLocation());

    if(desc == null){

      // Desc will be null if its CREATE TABLE LIKE. Desc will be contained

      // in CreateTableLikeDesc. Currently, Howl disallows CTLT in pre-hook.

      // So, desc can never be null.

      return;

    }

    Map<String,String> tblProps = desc.getTblProps();

    if(tblProps == null) {

      // tblProps will be null if user didnt use tblprops in his CREATE TABLE cmd.

      tblProps = new HashMap<String, String>();

    }

    tblProps.put(HowlConstants.HOWL_ISD_CLASS, inStorageDriver);

    tblProps.put(HowlConstants.HOWL_OSD_CLASS, outStorageDriver);

    desc.setTblProps(tblProps);

    context.getConf().set(HowlConstants.HOWL_CREATE_TBL_NAME, tableName);

  }

  private void authorize(HiveSemanticAnalyzerHookContext context, String loc) throws SemanticException{

    Path tblDir;

    Configuration conf = context.getConf();

    try {

      Warehouse wh = new Warehouse(conf);

      if (loc == null || loc.isEmpty()){

        tblDir = wh.getDnsPath(wh.getDefaultTablePath(context.getHive().getCurrentDatabase(), tableName).getParent());

      }

      else{

        tblDir = wh.getDnsPath(new Path(loc));

      }

      try {

        AuthUtils.authorize(tblDir, FsAction.WRITE, conf);

      } catch (HowlException e) {

        throw new SemanticException(e);

      }

    }

    catch (MetaException e) {

      throw new SemanticException(e);

    } catch (HiveException e) {

      throw new SemanticException(e);

    }

  }

}