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From vdiravka <...@git.apache.org>
Subject [GitHub] drill pull request #846: DRILL-5544: Out of heap running CTAS against text d...
Date Tue, 06 Jun 2017 16:10:02 GMT
Github user vdiravka commented on a diff in the pull request:

    https://github.com/apache/drill/pull/846#discussion_r119835458
  
    --- Diff: exec/java-exec/src/main/java/org/apache/parquet/hadoop/ParquetColumnChunkPageWriteStore.java
---
    @@ -0,0 +1,269 @@
    +/*
    + * 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 static org.apache.parquet.column.statistics.Statistics.getStatsBasedOnType;
    +
    +import java.io.Closeable;
    +import java.io.IOException;
    +import java.util.List;
    +import java.util.Map;
    +import java.util.Set;
    +
    +import com.google.common.collect.Lists;
    +import com.google.common.collect.Maps;
    +import com.google.common.collect.Sets;
    +import org.apache.drill.exec.store.parquet.ParquetDirectByteBufferAllocator;
    +import org.apache.parquet.bytes.BytesInput;
    +import org.apache.parquet.bytes.CapacityByteArrayOutputStream;
    +import org.apache.parquet.column.ColumnDescriptor;
    +import org.apache.parquet.column.Encoding;
    +import org.apache.parquet.column.page.DictionaryPage;
    +import org.apache.parquet.column.page.PageWriteStore;
    +import org.apache.parquet.column.page.PageWriter;
    +import org.apache.parquet.column.statistics.Statistics;
    +import org.apache.parquet.format.converter.ParquetMetadataConverter;
    +import org.apache.parquet.hadoop.CodecFactory.BytesCompressor;
    +import org.apache.parquet.io.ParquetEncodingException;
    +import org.apache.parquet.schema.MessageType;
    +import org.apache.parquet.bytes.ByteBufferAllocator;
    +import org.slf4j.Logger;
    +import org.slf4j.LoggerFactory;
    +
    +/**
    + * This is a copy of ColumnChunkPageWriteStore from parquet library except of OutputStream
that is used here.
    + * Using of CapacityByteArrayOutputStream allows to use different ByteBuffer allocators.
    --- End diff --
    
    To avoid of frequent I/O writes to the disk, parquet library buffers an every page as
`OutputStream` and writes the data only when `ColumnWriteStore` size is reached the block
size [[link](https://github.com/apache/drill/blob/874bf6296dcd1a42c7cf7f097c1a6b5458010cbb/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetRecordWriter.java#L288)].
For large block size value and big number of runs a lot of memory can be used before flushing
the data. 
    And using of ByteBuffers can allow to choose the type of memory to use. 
    
    `ColumnChunkPageWriter` used `CapacityByteArrayOutputStream` insted of `ByteArrayOutputStream`
and `ConcatenatingByteArrayCollector` before [PARQUET-160 fix](https://github.com/apache/parquet-mr/pull/98/commits/8b54667650873c03ea66721d0f06bfad0b968f19).
The fact that `ByteBufferAllocator` was introduced in PARQUET-77, but never used in the `ColumnChunkPageWriter`.
    
    See the explanation of why direct memory is more suitable for buffering than heap space
in the next comment.


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