parquet-column/src/main/java/parquet/schema/ConversionPatterns.java

/**
 * Copyright 2012 Twitter, Inc.
 *
 * Licensed 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 parquet.schema;

import static parquet.schema.OriginalType.*;
import parquet.schema.PrimitiveType.PrimitiveTypeName;
import parquet.schema.Type.Repetition;

/**
 * Utility functions to convert from Java-like map and list types
 * to equivalent Parquet types.
 *
 * TODO(julien): this class appears to be unused. Is it dead code?
 */
public abstract class ConversionPatterns {
  /**
   * to preserve the difference between empty list and null when optional
   * @param repetition
   * @param alias name of the field
   * @param originalType
   * @param nested the nested repeated field
   * @return a group type
   */
  private static GroupType listWrapper(Repetition repetition, String alias, OriginalType originalType, Type nested) {
    if (nested.getRepetition() != Repetition.REPEATED) {
      throw new IllegalArgumentException("Nested type should be repeated: " + nested);
    }
    return new GroupType(repetition, alias, originalType, nested);
  }

  public static GroupType mapType(Repetition repetition, String alias, Type valueType) {
    if (!valueType.getName().equals("value")) {
      throw new RuntimeException(valueType.getName() + " should be value");
    }
    return listWrapper(
        repetition,
        alias,
        MAP,
        new GroupType(
            Repetition.REPEATED,
            "map",
            MAP_KEY_VALUE,
            new PrimitiveType(Repetition.REQUIRED, PrimitiveTypeName.BINARY, "key"),
            valueType)
        );
  }

  /**
   *
   * @param repetition
   * @param alias name of the field
   * @param nestedType
   * @return
   */
  public static GroupType listType(Repetition repetition, String alias, Type nestedType) {
    return listWrapper(
        repetition,
        alias,
        LIST,
        nestedType
        );
  }
}