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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5356) Refactor Parquet Record Reader
Date Mon, 03 Apr 2017 23:57:42 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5356?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15954366#comment-15954366

ASF GitHub Bot commented on DRILL-5356:

Github user paul-rogers commented on a diff in the pull request:

    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/columnreaders/ParquetSchema.java
    @@ -0,0 +1,207 @@
    + * 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 java.util.ArrayList;
    +import java.util.Arrays;
    +import java.util.Collection;
    +import java.util.HashMap;
    +import java.util.List;
    +import java.util.Map;
    +import org.apache.drill.common.expression.SchemaPath;
    +import org.apache.drill.common.types.TypeProtos;
    +import org.apache.drill.common.types.Types;
    +import org.apache.drill.common.types.TypeProtos.DataMode;
    +import org.apache.drill.exec.exception.SchemaChangeException;
    +import org.apache.drill.exec.expr.TypeHelper;
    +import org.apache.drill.exec.physical.impl.OutputMutator;
    +import org.apache.drill.exec.record.MaterializedField;
    +import org.apache.drill.exec.server.options.OptionManager;
    +import org.apache.drill.exec.store.parquet.ParquetReaderUtility;
    +import org.apache.drill.exec.vector.NullableIntVector;
    +import org.apache.parquet.column.ColumnDescriptor;
    +import org.apache.parquet.format.SchemaElement;
    +import org.apache.parquet.hadoop.metadata.BlockMetaData;
    +import org.apache.parquet.hadoop.metadata.ColumnChunkMetaData;
    +import org.apache.parquet.hadoop.metadata.ParquetMetadata;
    +import com.google.common.collect.Lists;
    + * Mapping from the schema of the Parquet file to that of the record reader
    + * to the schema that Drill and the Parquet reader uses.
    + */
    +public class ParquetSchema {
    +  private Collection<SchemaPath> selectedCols;
    +  // This is a parallel list to the columns list above, it is used to determine the subset
of the project
    +  // pushdown columns that do not appear in this file
    +  private boolean[] columnsFound;
    +  private ParquetMetadata footer;
    +  private Map<String, SchemaElement> schemaElements;
    +  private int columnsToScan;
    +  private List<ColumnDescriptor> columns;
    +  private List<ParquetColumnMetadata> columnMd = new ArrayList<>();
    +  private int bitWidthAllFixedFields;
    +  private boolean allFieldsFixedLength = true;
    +  private long groupRecordCount;
    +  private int recordsPerBatch;
    +  private int rowGroupIndex;
    +  private final OptionManager options;
    +  public ParquetSchema(OptionManager options, int rowGroupIndex) {
    +    selectedCols = null;
    +    this.rowGroupIndex = rowGroupIndex;
    +    this.options = options;
    +  }
    +  public ParquetSchema(OptionManager options, Collection<SchemaPath> selectedCols)
    +    this.options = options;
    --- End diff --
    Merged constructors as suggested and added comments. Please let me know where additional
comments are needed to clarify what's happening.

> Refactor Parquet Record Reader
> ------------------------------
>                 Key: DRILL-5356
>                 URL: https://issues.apache.org/jira/browse/DRILL-5356
>             Project: Apache Drill
>          Issue Type: Improvement
>    Affects Versions: 1.10.0, 1.11.0
>            Reporter: Paul Rogers
>            Assignee: Paul Rogers
>            Priority: Minor
>             Fix For: 1.11.0
> The Parquet record reader class is a key part of Drill that has evolved over time to
become somewhat hard to follow.
> A number of us are working on Parquet-related tasks and find we have to spend an uncomfortable
amount of time trying to understand the code. In particular, this writer needs to figure out
how to convince the reader to provide higher-density record batches.
> Rather than continue to decypher the complex code multiple times, this ticket requests
to refactor the code to make it functionally identical, but structurally cleaner. The result
will be faster time to value when working with this code.
> This is a lower-priority change and will be coordinated with others working on this code
base. This ticket is only for the record reader class itself; it does not include the various
readers and writers that Parquet uses since another project is actively modifying those classes.

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