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From paul-rogers <...@git.apache.org>
Subject [GitHub] drill pull request #611: Drill-4800: Improve parquet reader performance
Date Thu, 03 Nov 2016 18:05:58 GMT
Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/611#discussion_r86395782
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/util/filereader/BufferedDirectBufInputStream.java
---
    @@ -0,0 +1,460 @@
    +/**
    + * 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
    + * <p/>
    + * http://www.apache.org/licenses/LICENSE-2.0
    + * <p/>
    + * 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.util.filereader;
    +
    +import com.google.common.base.Preconditions;
    +import io.netty.buffer.DrillBuf;
    +import org.apache.drill.common.config.DrillConfig;
    +import org.apache.drill.exec.memory.BufferAllocator;
    +import org.apache.drill.exec.memory.RootAllocatorFactory;
    +import org.apache.hadoop.conf.Configuration;
    +import org.apache.hadoop.fs.ByteBufferReadable;
    +import org.apache.hadoop.fs.FSDataInputStream;
    +import org.apache.hadoop.fs.FileSystem;
    +import org.apache.hadoop.fs.Path;
    +import org.apache.parquet.hadoop.Footer;
    +import org.apache.parquet.hadoop.ParquetFileReader;
    +import org.apache.parquet.hadoop.metadata.BlockMetaData;
    +import org.apache.parquet.hadoop.metadata.ColumnChunkMetaData;
    +import org.apache.parquet.hadoop.util.CompatibilityUtil;
    +
    +import java.io.Closeable;
    +import java.io.IOException;
    +import java.io.InputStream;
    +import java.nio.ByteBuffer;
    +import java.util.List;
    +
    +/**
    + * <code>BufferedDirectBufInputStream</code>  reads from the
    + * underlying <code>InputStream</code> in blocks of data, into an
    + * internal buffer. The internal buffer is a direct memory backed
    + * buffer. The implementation is similar to the <code>BufferedInputStream</code>
    + * class except that the internal buffer is a Drillbuf and
    + * not a byte array. The mark and reset methods of the underlying
    + * <code>InputStream</code>are not supported.
    --- End diff --
    
    Is this class entirely necessary? A buffers input stream uses heap memory, but does so
in a known way. Buffers are of limited life and limited size. Is the benefit of using direct
memory worth the cost of creating, testing and maintaining a separate class? If so, perhaps
the comment can explain that benefit and why using heap memory here is not a good idea.


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