parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ColumnChunkPageReadStore.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.hadoop;

import java.io.IOException;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;

import org.apache.parquet.Ints;
import org.apache.parquet.Log;
import org.apache.parquet.column.ColumnDescriptor;
import org.apache.parquet.column.page.DataPage;
import org.apache.parquet.column.page.DataPageV1;
import org.apache.parquet.column.page.DataPageV2;
import org.apache.parquet.column.page.DictionaryPage;
import org.apache.parquet.column.page.DictionaryPageReadStore;
import org.apache.parquet.column.page.PageReadStore;
import org.apache.parquet.column.page.PageReader;
import org.apache.parquet.hadoop.CodecFactory.BytesDecompressor;
import org.apache.parquet.io.ParquetDecodingException;

/**
 * TODO: should this actually be called RowGroupImpl or something?
 * The name is kind of confusing since it references three different "entities"
 * in our format: columns, chunks, and pages
 *
 */
class ColumnChunkPageReadStore implements PageReadStore, DictionaryPageReadStore {
  private static final Log LOG = Log.getLog(ColumnChunkPageReadStore.class);

  /**
   * PageReader for a single column chunk. A column chunk contains
   * several pages, which are yielded one by one in order.
   *
   * This implementation is provided with a list of pages, each of which
   * is decompressed and passed through.
   */
  static final class ColumnChunkPageReader implements PageReader {

    private final BytesDecompressor decompressor;
    private final long valueCount;
    private final List<DataPage> compressedPages;
    private final DictionaryPage compressedDictionaryPage;

    ColumnChunkPageReader(BytesDecompressor decompressor, List<DataPage> compressedPages, DictionaryPage compressedDictionaryPage) {
      this.decompressor = decompressor;
      this.compressedPages = new LinkedList<DataPage>(compressedPages);
      this.compressedDictionaryPage = compressedDictionaryPage;
      long count = 0;
      for (DataPage p : compressedPages) {
        count += p.getValueCount();
      }
      this.valueCount = count;
    }

    @Override
    public long getTotalValueCount() {
      return valueCount;
    }

    @Override
    public DataPage readPage() {
      if (compressedPages.isEmpty()) {
        return null;
      }
      DataPage compressedPage = compressedPages.remove(0);
      return compressedPage.accept(new DataPage.Visitor<DataPage>() {
        @Override
        public DataPage visit(DataPageV1 dataPageV1) {
          try {
            return new DataPageV1(
                decompressor.decompress(dataPageV1.getBytes(), dataPageV1.getUncompressedSize()),
                dataPageV1.getValueCount(),
                dataPageV1.getUncompressedSize(),
                dataPageV1.getStatistics(),
                dataPageV1.getRlEncoding(),
                dataPageV1.getDlEncoding(),
                dataPageV1.getValueEncoding());
          } catch (IOException e) {
            throw new ParquetDecodingException("could not decompress page", e);
          }
        }

        @Override
        public DataPage visit(DataPageV2 dataPageV2) {
          if (!dataPageV2.isCompressed()) {
            return dataPageV2;
          }
          try {
            int uncompressedSize = Ints.checkedCast(
                dataPageV2.getUncompressedSize()
                - dataPageV2.getDefinitionLevels().size()
                - dataPageV2.getRepetitionLevels().size());
            return DataPageV2.uncompressed(
                dataPageV2.getRowCount(),
                dataPageV2.getNullCount(),
                dataPageV2.getValueCount(),
                dataPageV2.getRepetitionLevels(),
                dataPageV2.getDefinitionLevels(),
                dataPageV2.getDataEncoding(),
                decompressor.decompress(dataPageV2.getData(), uncompressedSize),
                dataPageV2.getStatistics()
                );
          } catch (IOException e) {
            throw new ParquetDecodingException("could not decompress page", e);
          }
        }
      });
    }

    @Override
    public DictionaryPage readDictionaryPage() {
      if (compressedDictionaryPage == null) {
        return null;
      }
      try {
        return new DictionaryPage(
            decompressor.decompress(compressedDictionaryPage.getBytes(), compressedDictionaryPage.getUncompressedSize()),
            compressedDictionaryPage.getDictionarySize(),
            compressedDictionaryPage.getEncoding());
      } catch (IOException e) {
        throw new ParquetDecodingException("Could not decompress dictionary page", e);
      }
    }
  }

  private final Map<ColumnDescriptor, ColumnChunkPageReader> readers = new HashMap<ColumnDescriptor, ColumnChunkPageReader>();
  private final long rowCount;

  public ColumnChunkPageReadStore(long rowCount) {
    this.rowCount = rowCount;
  }

  @Override
  public long getRowCount() {
    return rowCount;
  }

  @Override
  public PageReader getPageReader(ColumnDescriptor path) {
    if (!readers.containsKey(path)) {
      throw new IllegalArgumentException(path + " is not in the store: " + readers.keySet() + " " + rowCount);
    }
    return readers.get(path);
  }

  @Override
  public DictionaryPage readDictionaryPage(ColumnDescriptor descriptor) {
    return readers.get(descriptor).readDictionaryPage();
  }

  void addColumn(ColumnDescriptor path, ColumnChunkPageReader reader) {
    if (readers.put(path, reader) != null) {
      throw new RuntimeException(path+ " was added twice");
    }
  }

}