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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DRILL-5379) Set Hdfs Block Size based on Parquet Block Size
Date Wed, 17 May 2017 21:18:04 GMT

    [ https://issues.apache.org/jira/browse/DRILL-5379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16014792#comment-16014792
] 

ASF GitHub Bot commented on DRILL-5379:
---------------------------------------

Github user ppadma commented on a diff in the pull request:

    https://github.com/apache/drill/pull/826#discussion_r117112378
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetRecordWriter.java
---
    @@ -380,14 +384,21 @@ public void endRecord() throws IOException {
     
           // since ParquetFileWriter will overwrite empty output file (append is not supported)
           // we need to re-apply file permission
    -      parquetFileWriter = new ParquetFileWriter(conf, schema, path, ParquetFileWriter.Mode.OVERWRITE);
    +      if (useConfiguredBlockSize) {
    +        // Round up blockSize to multiple of 64K.
    +        long writeBlockSize = ((long) ceil((double)blockSize/BLOCKSIZE_MULTIPLE)) * BLOCKSIZE_MULTIPLE;
    +        // Passing writeBlockSize creates files with this blockSize instead of filesystem
default blockSize.
    +        // Currently, this is supported only by filesystems included in
    +        // BLOCK_FS_SCHEMES (ParquetFileWriter.java in parquet-mr), which includes HDFS.
    +        // For other filesystems, it uses default blockSize configured for the file system.
    +        parquetFileWriter = new ParquetFileWriter(conf, schema, path, ParquetFileWriter.Mode.OVERWRITE,
writeBlockSize, 0);
    +      } else {
    +        parquetFileWriter = new ParquetFileWriter(conf, schema, path, ParquetFileWriter.Mode.OVERWRITE);
    --- End diff --
    
    No. It does not. If user had previously changed the parquet block size, that will be used
in checkBlockSizeReached as before. So, parquet rowGroup size will be same as configured parquet
blockSize (not default). This option only changes the behavior of how we write that parquet
row group onto disk i.e. single block or not. 


> Set Hdfs Block Size based on Parquet Block Size
> -----------------------------------------------
>
>                 Key: DRILL-5379
>                 URL: https://issues.apache.org/jira/browse/DRILL-5379
>             Project: Apache Drill
>          Issue Type: Improvement
>          Components: Storage - Parquet
>    Affects Versions: 1.9.0
>            Reporter: F M├ęthot
>             Fix For: Future
>
>
> It seems there a way to force Drill to store CTAS generated parquet file as a single
block when using HDFS. Java HDFS API allows to do that, files could be created with the Parquet
block-size set in a session or system config.
> Since it is ideal  to have single parquet file per hdfs block.
> Here is the HDFS API that allow to do that:
> http://archive.cloudera.com/cdh4/cdh/4/hadoop/api/org/apache/hadoop/fs/FileSystem.html#create(org.apache.hadoop.fs.Path,%20boolean,%20int,%20short,%20long)
> http://archive.cloudera.com/cdh4/cdh/4/hadoop/api/org/apache/hadoop/fs/FileSystem.html#create(org.apache.hadoop.fs.Path,%20boolean,%20int,%20short,%20long)
> Drill uses the hadoop ParquetFileWriter (https://github.com/Parquet/parquet-mr/blob/master/parquet-hadoop/src/main/java/parquet/hadoop/ParquetFileWriter.java).
> This is where the file creation occurs so it might be tricky.
> However, ParquetRecordWriter.java (https://github.com/apache/drill/blob/master/exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetRecordWriter.java)
in Drill creates the ParquetFileWriter with an hadoop configuration object.
> something to explore: Could the block size be set as a property within the Configuration
object before passing it to ParquetFileWriter constructor?



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