exec/vector/src/main/java/org/apache/drill/exec/vector/accessor/TupleReader.java

/*
 * 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.drill.exec.vector.accessor;

import org.apache.drill.exec.record.metadata.TupleMetadata;

/**
 * Interface for reading from tuples (rows or maps). Provides
 * a column reader for each column that can be obtained either
 * by name or column index (as defined in the tuple schema.)
 * Also provides two generic methods to get the value as a
 * Java object or as a string.
 *
 * @see {@link TupleWriter}
 */

public interface TupleReader extends ColumnReader {
  TupleMetadata tupleSchema();
  int columnCount();

  /**
   * Return a column reader by column index as reported by the
   * associated metadata.
   *
   * @param colIndex column index
   * @return reader for the column
   * @throws {@link java.lang.IndexOutOfBoundsException} if the index is invalid
   */

  ObjectReader column(int colIndex);

  /**
   * Return a column reader by name.
   *
   * @param colName column name
   * @return reader for the column, or <tt>null</tt> if no such
   * column exists
   */

  ObjectReader column(String colName);

  // Convenience methods

  ObjectType type(int colIndex);
  ObjectType type(String colName);
  ScalarReader scalar(int colIndex);
  ScalarReader scalar(String colName);
  TupleReader tuple(int colIndex);
  TupleReader tuple(String colName);
  ArrayReader array(int colIndex);
  ArrayReader array(String colName);
  VariantReader variant(int colIndex);
  VariantReader variant(String colName);
  DictReader dict(int colIndex);
  DictReader dict(String colName);
}