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From ppadma <...@git.apache.org>
Subject [GitHub] drill pull request #611: Drill-4800: Improve parquet reader performance
Date Wed, 26 Oct 2016 16:01:26 GMT
Github user ppadma commented on a diff in the pull request:

    https://github.com/apache/drill/pull/611#discussion_r84972962
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/columnreaders/AsyncPageReader.java
---
    @@ -0,0 +1,409 @@
    +/**
    + * 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.store.parquet.columnreaders;
    +
    +import com.google.common.base.Stopwatch;
    +import io.netty.buffer.DrillBuf;
    +import io.netty.buffer.ByteBufUtil;
    +import org.apache.drill.common.exceptions.ExecutionSetupException;
    +import org.apache.drill.common.exceptions.UserException;
    +import org.apache.hadoop.io.compress.Decompressor;
    +import org.apache.hadoop.io.compress.DirectDecompressor;
    +import org.apache.hadoop.io.compress.GzipCodec;
    +import org.apache.parquet.hadoop.CodecFactory;
    +import org.apache.parquet.hadoop.codec.SnappyCodec;
    +import org.apache.parquet.hadoop.metadata.ColumnChunkMetaData;
    +import org.apache.drill.exec.util.filereader.DirectBufInputStream;
    +import org.apache.hadoop.fs.FileSystem;
    +import org.apache.hadoop.fs.Path;
    +import org.apache.parquet.column.page.DictionaryPage;
    +import org.apache.parquet.format.PageHeader;
    +import org.apache.parquet.format.PageType;
    +import org.apache.parquet.format.Util;
    +import org.apache.parquet.hadoop.metadata.CompressionCodecName;
    +import org.xerial.snappy.Snappy;
    +
    +import java.io.IOException;
    +import java.nio.ByteBuffer;
    +import java.util.concurrent.Callable;
    +import java.util.concurrent.ExecutorService;
    +import java.util.concurrent.Future;
    +import java.util.concurrent.TimeUnit;
    +
    +import static org.apache.parquet.column.Encoding.valueOf;
    +
    +class AsyncPageReader extends PageReader {
    +  static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(AsyncPageReader.class);
    +
    +
    +  private ExecutorService threadPool;
    +  private Future<ReadStatus> asyncPageRead;
    +
    +  AsyncPageReader(ColumnReader<?> parentStatus, FileSystem fs, Path path,
    +      ColumnChunkMetaData columnChunkMetaData) throws ExecutionSetupException {
    +    super(parentStatus, fs, path, columnChunkMetaData);
    +    if (threadPool == null) {
    +      threadPool = parentColumnReader.parentReader.getOperatorContext().getScanExecutor();
    +    }
    +    asyncPageRead = threadPool.submit(new AsyncPageReaderTask());
    +  }
    +
    +  @Override protected void loadDictionaryIfExists(final ColumnReader<?> parentStatus,
    +      final ColumnChunkMetaData columnChunkMetaData, final DirectBufInputStream f) throws
UserException {
    +    if (columnChunkMetaData.getDictionaryPageOffset() > 0) {
    +      try {
    +        dataReader.skip(columnChunkMetaData.getDictionaryPageOffset() - dataReader.getPos());
    +      } catch (IOException e) {
    +        handleAndThrowException(e, "Error Reading dictionary page.");
    +      }
    +      // parent constructor may call this method before the thread pool is set.
    +      if (threadPool == null) {
    +        threadPool = parentColumnReader.parentReader.getOperatorContext().getScanExecutor();
    +      }
    +      asyncPageRead = threadPool.submit(new AsyncPageReaderTask());
    +      readDictionaryPage(asyncPageRead, parentStatus);
    +      asyncPageRead = null; // reset after consuming
    +    }
    +  }
    +
    +  private DrillBuf getDecompressedPageData(ReadStatus readStatus) {
    +    DrillBuf data;
    +    boolean isDictionary = false;
    +    synchronized (this) {
    +      data = readStatus.getPageData();
    +      readStatus.setPageData(null);
    +      isDictionary = readStatus.isDictionaryPage;
    +    }
    +    if (parentColumnReader.columnChunkMetaData.getCodec() != CompressionCodecName.UNCOMPRESSED)
{
    +      DrillBuf uncompressedData = data;
    +      data = decompress(readStatus.getPageHeader(), uncompressedData);
    +      synchronized (this) {
    +        readStatus.setPageData(null);
    +      }
    +      uncompressedData.release();
    +    } else {
    +      if (isDictionary) {
    +        stats.totalDictPageReadBytes.addAndGet(readStatus.bytesRead);
    +      } else {
    +        stats.totalDataPageReadBytes.addAndGet(readStatus.bytesRead);
    +      }
    +    }
    +    return data;
    +  }
    +
    +  // Read and decode the dictionary and the header
    +  private void readDictionaryPage(final Future<ReadStatus> asyncPageRead,
    +      final ColumnReader<?> parentStatus) throws UserException {
    +    try {
    +      Stopwatch timer = Stopwatch.createStarted();
    +      ReadStatus readStatus = asyncPageRead.get();
    +      long timeBlocked = timer.elapsed(TimeUnit.NANOSECONDS);
    +      stats.timeDiskScanWait.addAndGet(timeBlocked);
    +      stats.timeDiskScan.addAndGet(readStatus.getDiskScanTime());
    +      stats.numDictPageLoads.incrementAndGet();
    +      stats.timeDictPageLoads.addAndGet(timeBlocked+readStatus.getDiskScanTime());
    +      readDictionaryPageData(readStatus, parentStatus);
    +    } catch (Exception e) {
    +      handleAndThrowException(e, "Error reading dictionary page.");
    +    }
    +  }
    +
    +  // Read and decode the dictionary data
    +  private void readDictionaryPageData(final ReadStatus readStatus, final ColumnReader<?>
parentStatus)
    +      throws UserException {
    +    try {
    +      pageHeader = readStatus.getPageHeader();
    +      int uncompressedSize = pageHeader.getUncompressed_page_size();
    +      final DrillBuf dictionaryData = getDecompressedPageData(readStatus);
    +      Stopwatch timer = Stopwatch.createStarted();
    +      allocatedDictionaryBuffers.add(dictionaryData);
    +      DictionaryPage page = new DictionaryPage(asBytesInput(dictionaryData, 0, uncompressedSize),
    +          pageHeader.uncompressed_page_size, pageHeader.dictionary_page_header.num_values,
    +          valueOf(pageHeader.dictionary_page_header.encoding.name()));
    +      this.dictionary = page.getEncoding().initDictionary(parentStatus.columnDescriptor,
page);
    +      long timeToDecode = timer.elapsed(TimeUnit.NANOSECONDS);
    +      stats.timeDictPageDecode.addAndGet(timeToDecode);
    +    } catch (Exception e) {
    +      handleAndThrowException(e, "Error decoding dictionary page.");
    +    }
    +  }
    +
    +  private void handleAndThrowException(Exception e, String msg) throws UserException
{
    +    UserException ex = UserException.dataReadError(e).message(msg)
    +        .pushContext("Row Group Start: ", this.parentColumnReader.columnChunkMetaData.getStartingPos())
    +        .pushContext("Column: ", this.parentColumnReader.schemaElement.getName())
    +        .pushContext("File: ", this.fileName).build(logger);
    +    throw ex;
    +  }
    +
    +  private DrillBuf decompress(PageHeader pageHeader, DrillBuf compressedData) {
    +    DrillBuf pageDataBuf = null;
    +    Stopwatch timer = Stopwatch.createUnstarted();
    +    long timeToRead;
    +    int compressedSize = pageHeader.getCompressed_page_size();
    +    int uncompressedSize = pageHeader.getUncompressed_page_size();
    +    pageDataBuf = allocateTemporaryBuffer(uncompressedSize);
    +    try {
    +      timer.start();
    +      CompressionCodecName codecName = parentColumnReader.columnChunkMetaData.getCodec();
    +      ByteBuffer input = compressedData.nioBuffer(0, compressedSize);
    +      ByteBuffer output = pageDataBuf.nioBuffer(0, uncompressedSize);
    +      DecompressionHelper decompressionHelper = new DecompressionHelper(codecName);
    +      decompressionHelper.decompress(input, compressedSize, output, uncompressedSize);
    +      pageDataBuf.writerIndex(uncompressedSize);
    +      timeToRead = timer.elapsed(TimeUnit.NANOSECONDS);
    +      this.updateStats(pageHeader, "Decompress", 0, timeToRead, compressedSize, uncompressedSize);
    +    } catch (IOException e) {
    +      handleAndThrowException(e, "Error decompressing data.");
    +    }
    +    return pageDataBuf;
    +  }
    +
    +  @Override protected void nextInternal() throws IOException {
    +    ReadStatus readStatus = null;
    +    try {
    +      Stopwatch timer = Stopwatch.createStarted();
    +      readStatus = asyncPageRead.get();
    +      long timeBlocked = timer.elapsed(TimeUnit.NANOSECONDS);
    +      stats.timeDiskScanWait.addAndGet(timeBlocked);
    +      stats.timeDiskScan.addAndGet(readStatus.getDiskScanTime());
    +      if (readStatus.isDictionaryPage) {
    +        stats.numDictPageLoads.incrementAndGet();
    +        stats.timeDictPageLoads.addAndGet(timeBlocked + readStatus.getDiskScanTime());
    +      } else {
    +        stats.numDataPageLoads.incrementAndGet();
    +        stats.timeDataPageLoads.addAndGet(timeBlocked + readStatus.getDiskScanTime());
    +      }
    +      pageHeader = readStatus.getPageHeader();
    +      // reset this. At the time of calling close, if this is not null then a pending
asyncPageRead needs to be consumed
    +      asyncPageRead = null;
    +    } catch (Exception e) {
    +      handleAndThrowException(e, "Error reading page data.");
    +    }
    +
    +    // TODO - figure out if we need multiple dictionary pages, I believe it may be limited
to one
    +    // I think we are clobbering parts of the dictionary if there can be multiple pages
of dictionary
    +
    +    do {
    +      if (pageHeader.getType() == PageType.DICTIONARY_PAGE) {
    +        readDictionaryPageData(readStatus, parentColumnReader);
    +        // Ugly. Use the Async task to make a synchronous read call.
    +        readStatus = new AsyncPageReaderTask().call();
    +        pageHeader = readStatus.getPageHeader();
    +      }
    +    } while (pageHeader.getType() == PageType.DICTIONARY_PAGE);
    +
    +    if (parentColumnReader.totalValuesRead + readStatus.getValuesRead()
    +        < parentColumnReader.columnChunkMetaData.getValueCount()) {
    +      asyncPageRead = threadPool.submit(new AsyncPageReaderTask());
    +    }
    +
    +    pageHeader = readStatus.getPageHeader();
    +    pageData = getDecompressedPageData(readStatus);
    +
    +
    +  }
    +
    +
    +  @Override public void clear() {
    +    if (asyncPageRead != null) {
    +      try {
    +        ReadStatus r = asyncPageRead.get();
    +        r.getPageData().release();
    +      } catch (Exception e) {
    +        // Do nothing.
    +      }
    +    }
    +    super.clear();
    +  }
    +
    +  public static class ReadStatus {
    +    private PageHeader pageHeader;
    +    private DrillBuf pageData;
    +    private boolean isDictionaryPage = false;
    +    private long bytesRead = 0;
    +    private long valuesRead = 0;
    +    private long diskScanTime = 0;
    +
    +    public synchronized PageHeader getPageHeader() {
    +      return pageHeader;
    +    }
    +
    +    public synchronized void setPageHeader(PageHeader pageHeader) {
    +      this.pageHeader = pageHeader;
    +    }
    +
    +    public synchronized DrillBuf getPageData() {
    +      return pageData;
    +    }
    +
    +    public synchronized void setPageData(DrillBuf pageData) {
    +      this.pageData = pageData;
    +    }
    +
    +    public synchronized boolean isDictionaryPage() {
    +      return isDictionaryPage;
    +    }
    +
    +    public synchronized void setIsDictionaryPage(boolean isDictionaryPage) {
    +      this.isDictionaryPage = isDictionaryPage;
    +    }
    +
    +    public synchronized long getBytesRead() {
    +      return bytesRead;
    +    }
    +
    +    public synchronized void setBytesRead(long bytesRead) {
    +      this.bytesRead = bytesRead;
    +    }
    +
    +    public synchronized long getValuesRead() {
    +      return valuesRead;
    +    }
    +
    +    public synchronized void setValuesRead(long valuesRead) {
    +      this.valuesRead = valuesRead;
    +    }
    +
    +    public long getDiskScanTime() {
    +      return diskScanTime;
    +    }
    +
    +    public void setDiskScanTime(long diskScanTime) {
    +      this.diskScanTime = diskScanTime;
    +    }
    +  }
    +
    +
    +  private class AsyncPageReaderTask implements Callable<ReadStatus> {
    +
    +    private final AsyncPageReader parent = AsyncPageReader.this;
    +
    +    public AsyncPageReaderTask() {
    +    }
    +
    +    @Override public ReadStatus call() throws IOException {
    +      ReadStatus readStatus = new ReadStatus();
    +
    +      String oldname = Thread.currentThread().getName();
    +      String name = parent.parentColumnReader.columnChunkMetaData.toString();
    +      Thread.currentThread().setName(name);
    +
    +      long bytesRead = 0;
    +      long valuesRead = 0;
    +      Stopwatch timer = Stopwatch.createStarted();
    +
    +      DrillBuf pageData = null;
    +      try {
    +        long s = parent.dataReader.getPos();
    +        PageHeader pageHeader = Util.readPageHeader(parent.dataReader);
    +        long e = parent.dataReader.getPos();
    +        if(logger.isTraceEnabled()) {
    +          logger.trace("[{}]: Read Page Header : ReadPos = {} : Bytes Read = {} ", name,
s, e - s);
    +        }
    +        int compressedSize = pageHeader.getCompressed_page_size();
    +        s = parent.dataReader.getPos();
    +        pageData = parent.dataReader.getNext(compressedSize);
    +        e = parent.dataReader.getPos();
    +        bytesRead = compressedSize;
    +
    +        if(logger.isTraceEnabled()) {
    +          DrillBuf bufStart = pageData.slice(0, compressedSize>100?100:compressedSize);
    +          int endOffset = compressedSize>100?compressedSize-100:0;
    +          DrillBuf bufEnd = pageData.slice(endOffset, compressedSize-endOffset);
    +          logger
    +              .trace("[{}]: Read Page Data : ReadPos = {} : Bytes Read = {} : Buf Start
= {} : Buf End = {} ",
    +                  name, s, e - s, ByteBufUtil.hexDump(bufStart), ByteBufUtil.hexDump(bufEnd));
    +
    +        }
    +
    +        synchronized (parent) {
    +          if (pageHeader.getType() == PageType.DICTIONARY_PAGE) {
    +            readStatus.setIsDictionaryPage(true);
    +            valuesRead += pageHeader.getDictionary_page_header().getNum_values();
    +          } else {
    +            valuesRead += pageHeader.getData_page_header().getNum_values();
    +          }
    +          long timeToRead = timer.elapsed(TimeUnit.NANOSECONDS);
    +          readStatus.setPageHeader(pageHeader);
    +          readStatus.setPageData(pageData);
    +          readStatus.setBytesRead(bytesRead);
    +          readStatus.setValuesRead(valuesRead);
    +          readStatus.setDiskScanTime(timeToRead);
    +        }
    +
    +      } catch (Exception e) {
    +        if (pageData != null) {
    +          pageData.release();
    +        }
    +        throw e;
    +      }
    +      Thread.currentThread().setName(oldname);
    +      return readStatus;
    +    }
    +
    +  }
    +
    +  private class DecompressionHelper {
    +    final CompressionCodecName codecName;
    +
    +    public DecompressionHelper(CompressionCodecName codecName){
    +      this.codecName = codecName;
    +    }
    +
    +    public void decompress (ByteBuffer input, int compressedSize, ByteBuffer output,
int uncompressedSize)
    +        throws IOException {
    +      // GZip != thread_safe, so we go off and do our own thing.
    +      // The hadoop interface does not support ByteBuffer so we incur some
    +      // expensive copying.
    +      if (codecName == CompressionCodecName.GZIP) {
    +        GzipCodec codec = new GzipCodec();
    +        DirectDecompressor directDecompressor = codec.createDirectDecompressor();
    +        if (directDecompressor != null) {
    +          logger.debug("Using GZIP direct decompressor.");
    +          directDecompressor.decompress(input, output);
    +        } else {
    +          logger.debug("Using GZIP (in)direct decompressor.");
    +          Decompressor decompressor = codec.createDecompressor();
    +          decompressor.reset();
    +          byte[] inputBytes = new byte[compressedSize];
    +          input.position(0);
    +          input.get(inputBytes);
    +          decompressor.setInput(inputBytes, 0, inputBytes.length);
    +          byte[] outputBytes = new byte[uncompressedSize];
    +          decompressor.decompress(outputBytes, 0, uncompressedSize);
    +          output.clear();
    +          output.put(outputBytes);
    +        }
    +      } else if (codecName == CompressionCodecName.SNAPPY) {
    +        // For Snappy, just call the Snappy decompressor directly.
    +        // It is thread safe. The Hadoop layers though, appear to be
    +        // not quite reliable in a multithreaded environment
    --- End diff --
    
    Not sure what that comment means and what the implications are. May be you can improve
the comment :-)


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