[jira] [Resolved] (PARQUET-642) Improve performance of ByteBuffer based read / write paths

["Julien Le Dem (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PARQUET-642?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Julien Le Dem resolved PARQUET-642.
-----------------------------------
       Resolution: Fixed
    Fix Version/s: 1.9.0

Issue resolved by pull request 347
[https://github.com/apache/parquet-mr/pull/347]

> Improve performance of ByteBuffer based read / write paths
> ----------------------------------------------------------
>
>                 Key: PARQUET-642
>                 URL: https://issues.apache.org/jira/browse/PARQUET-642
>             Project: Parquet
>          Issue Type: Bug
>            Reporter: Piyush Narang
>            Assignee: Piyush Narang
>             Fix For: 1.9.0
>
>
> While trying out the newest Parquet version, we noticed that the changes to start using ByteBuffers: https://github.com/apache/parquet-mr/commit/6b605a4ea05b66e1a6bf843353abcb4834a4ced8 and https://github.com/apache/parquet-mr/commit/6b24a1d1b5e2792a7821ad172a45e38d2b04f9b8 (mostly avro but a couple of ByteBuffer changes) caused our jobs to slow down a bit. 
> Read overhead: 4-6% (in MB_Millis)
> Write overhead: 6-10% (MB_Millis). 
> Seems like this seems to be due to the encoding / decoding of Strings in the Binary class (https://github.com/apache/parquet-mr/blob/master/parquet-column/src/main/java/org/apache/parquet/io/api/Binary.java) - toStringUsingUTF8() - for reads
> encodeUTF8() - for writes
> In those methods we're using the nio Charsets for encode / decode:
> {code}
>     private static ByteBuffer encodeUTF8(CharSequence value) {
>       try {
>         return ENCODER.get().encode(CharBuffer.wrap(value));
>       } catch (CharacterCodingException e) {
>         throw new ParquetEncodingException("UTF-8 not supported.", e);
>       }
>     }
>   }
> ...
>     @Override
>     public String toStringUsingUTF8() {
>       int limit = value.limit();
>       value.limit(offset+length);
>       int position = value.position();
>       value.position(offset);
>       // no corresponding interface to read a subset of a buffer, would have to slice it
>       // which creates another ByteBuffer object or do what is done here to adjust the
>       // limit/offset and set them back after
>       String ret = UTF8.decode(value).toString();
>       value.limit(limit);
>       value.position(position);
>       return ret;
>     }
> {code}
> Tried out some micro / macro benchmarks and it seems like switching those out to using the String class for the encoding / decoding improves performance:
> {code}
> @Override
>     public String toStringUsingUTF8() {
>       String ret;
>       if (value.hasArray()) {
>         try {
>           ret = new String(value.array(), value.arrayOffset() + offset, length, "UTF-8");
>         } catch (UnsupportedEncodingException e) {
>           throw new ParquetDecodingException("UTF-8 not supported");
>         }
>       } else {
>         int limit = value.limit();
>         value.limit(offset+length);
>         int position = value.position();
>         value.position(offset);
>         // no corresponding interface to read a subset of a buffer, would have to slice it
>         // which creates another ByteBuffer object or do what is done here to adjust the
>         // limit/offset and set them back after
>         ret = UTF8.decode(value).toString();
>         value.limit(limit);
>         value.position(position);
>       }
>       return ret;
>     }
> ...
> private static ByteBuffer encodeUTF8(String value) {
>       try {
>         return ByteBuffer.wrap(value.getBytes("UTF-8"));
>       } catch (UnsupportedEncodingException e) {
>         throw new ParquetEncodingException("UTF-8 not supported.", e);
>       }
>     }
> {code}



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