Github user parthchandra commented on a diff in the pull request:
https://github.com/apache/drill/pull/611#discussion_r85248331
--- 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);
--- End diff --
Because this method has to block until it has the dictionary page(s) read.
This part of the code is simply retaining the old code that seems to imply that
more than one dictionary page may exist, though it is very unlikely to be so.
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