parquet-cli/src/main/java/org/apache/parquet/cli/commands/ShowDictionaryCommand.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.parquet.cli.commands;

import com.beust.jcommander.Parameter;
import com.beust.jcommander.Parameters;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import org.apache.parquet.cli.BaseCommand;
import org.apache.parquet.cli.Util;
import org.apache.parquet.column.ColumnDescriptor;
import org.apache.parquet.column.Dictionary;
import org.apache.parquet.column.page.DictionaryPage;
import org.apache.parquet.column.page.DictionaryPageReadStore;
import org.apache.parquet.hadoop.ParquetFileReader;
import org.apache.parquet.schema.LogicalTypeAnnotation;
import org.apache.parquet.schema.MessageType;
import org.apache.parquet.schema.PrimitiveType;
import org.slf4j.Logger;
import java.io.IOException;
import java.util.List;

// TODO: show dictionary size in values and in bytes
@Parameters(commandDescription="Print dictionaries for a Parquet column")
public class ShowDictionaryCommand extends BaseCommand {

  public ShowDictionaryCommand(Logger console) {
    super(console);
  }

  @Parameter(description = "<parquet path>")
  List<String> targets;

  @Parameter(
      names = {"-c", "--column"},
      description = "Column path",
      required = true)
  String column;

  @Override
  @SuppressWarnings("unchecked")
  public int run() throws IOException {
    Preconditions.checkArgument(targets != null && targets.size() >= 1,
        "A Parquet file is required.");
    Preconditions.checkArgument(targets.size() == 1,
        "Cannot process multiple Parquet files.");

    String source = targets.get(0);

    try (ParquetFileReader reader = ParquetFileReader.open(getConf(), qualifiedPath(source))) {
      MessageType schema = reader.getFileMetaData().getSchema();
      ColumnDescriptor descriptor = Util.descriptor(column, schema);
      PrimitiveType type = Util.primitive(column, schema);
      Preconditions.checkNotNull(type);

      DictionaryPageReadStore dictionaryReader;
      int rowGroup = 0;
      while ((dictionaryReader = reader.getNextDictionaryReader()) != null) {
        DictionaryPage page = dictionaryReader.readDictionaryPage(descriptor);

        Dictionary dict = page.getEncoding().initDictionary(descriptor, page);

        console.info("\nRow group {} dictionary for \"{}\":", rowGroup, column, page.getCompressedSize());
        for (int i = 0; i <= dict.getMaxId(); i += 1) {
          switch(type.getPrimitiveTypeName()) {
            case BINARY:
              if (type.getLogicalTypeAnnotation() instanceof LogicalTypeAnnotation.StringLogicalTypeAnnotation) {
                console.info("{}: {}", String.format("%6d", i),
                    Util.humanReadable(dict.decodeToBinary(i).toStringUsingUTF8(), 70));
              } else {
                console.info("{}: {}", String.format("%6d", i),
                    Util.humanReadable(dict.decodeToBinary(i).getBytesUnsafe(), 70));
              }
              break;
            case INT32:
              console.info("{}: {}", String.format("%6d", i),
                dict.decodeToInt(i));
              break;
            case INT64:
              console.info("{}: {}", String.format("%6d", i),
                  dict.decodeToLong(i));
              break;
            case FLOAT:
              console.info("{}: {}", String.format("%6d", i),
                  dict.decodeToFloat(i));
              break;
            case DOUBLE:
              console.info("{}: {}", String.format("%6d", i),
                  dict.decodeToDouble(i));
              break;
            default:
              throw new IllegalArgumentException(
                  "Unknown dictionary type: " + type.getPrimitiveTypeName());
          }
        }

        reader.skipNextRowGroup();

        rowGroup += 1;
      }
    }

    console.info("");

    return 0;
  }

  @Override
  public List<String> getExamples() {
    return Lists.newArrayList(
        "# Show the dictionary for column 'col' from a Parquet file",
        "-c col sample.parquet"
    );
  }
}