[jira] [Commented] (DRILL-5356) Refactor Parquet Record Reader

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-5356?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15954369#comment-15954369 ] 

ASF GitHub Bot commented on DRILL-5356:
---------------------------------------

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

    https://github.com/apache/drill/pull/789#discussion_r109511016
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/columnreaders/ParquetRecordReader.java ---
    @@ -307,164 +231,49 @@ public FragmentContext getFragmentContext() {
         return fragmentContext;
       }
     
    -  /**
    -   * Returns data type length for a given {@see ColumnDescriptor} and it's corresponding
    -   * {@see SchemaElement}. Neither is enough information alone as the max
    -   * repetition level (indicating if it is an array type) is in the ColumnDescriptor and
    -   * the length of a fixed width field is stored at the schema level.
    -   *
    -   * @return the length if fixed width, else -1
    -   */
    -  private int getDataTypeLength(ColumnDescriptor column, SchemaElement se) {
    -    if (column.getType() != PrimitiveType.PrimitiveTypeName.BINARY) {
    -      if (column.getMaxRepetitionLevel() > 0) {
    -        return -1;
    -      }
    -      if (column.getType() == PrimitiveType.PrimitiveTypeName.FIXED_LEN_BYTE_ARRAY) {
    -        return se.getType_length() * 8;
    -      } else {
    -        return getTypeLengthInBits(column.getType());
    -      }
    -    } else {
    -      return -1;
    -    }
    -  }
    -
    -  @SuppressWarnings({ "resource", "unchecked" })
       @Override
       public void setup(OperatorContext operatorContext, OutputMutator output) throws ExecutionSetupException {
         this.operatorContext = operatorContext;
    -    if (!isStarQuery()) {
    -      columnsFound = new boolean[getColumns().size()];
    -      nullFilledVectors = new ArrayList<>();
    +    if (isStarQuery()) {
    +      schema = new ParquetSchema(fragmentContext.getOptions(), rowGroupIndex);
    +    } else {
    +      schema = new ParquetSchema(fragmentContext.getOptions(), getColumns());
    --- End diff --
    
    Fixed. Added comments.


> 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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