hive-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "liyunzhang_intel (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-15527) Memory usage is unbound in SortByShuffler for Spark
Date Tue, 03 Jan 2017 02:52:58 GMT

    [ https://issues.apache.org/jira/browse/HIVE-15527?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15793967#comment-15793967
] 

liyunzhang_intel commented on HIVE-15527:
-----------------------------------------

[~xuefuz] and [~lirui]: HiveKVResultCache will write key value pair if buffer is full and
this will do some limits to the memory usage. But is there anything to show that the ArrayList
use a lot of memory? test this by memory analysis tool?



> Memory usage is unbound in SortByShuffler for Spark
> ---------------------------------------------------
>
>                 Key: HIVE-15527
>                 URL: https://issues.apache.org/jira/browse/HIVE-15527
>             Project: Hive
>          Issue Type: Improvement
>          Components: Spark
>    Affects Versions: 1.1.0
>            Reporter: Xuefu Zhang
>            Assignee: Xuefu Zhang
>         Attachments: HIVE-15527.1.patch, HIVE-15527.2.patch, HIVE-15527.3.patch, HIVE-15527.patch
>
>
> In SortByShuffler.java, an ArrayList is used to back the iterator for values that have
the same key in shuffled result produced by spark transformation sortByKey. It's possible
that memory can be exhausted because of a large key group.
> {code}
>             @Override
>             public Tuple2<HiveKey, Iterable<BytesWritable>> next() {
>               // TODO: implement this by accumulating rows with the same key into a list.
>               // Note that this list needs to improved to prevent excessive memory usage,
but this
>               // can be done in later phase.
>               while (it.hasNext()) {
>                 Tuple2<HiveKey, BytesWritable> pair = it.next();
>                 if (curKey != null && !curKey.equals(pair._1())) {
>                   HiveKey key = curKey;
>                   List<BytesWritable> values = curValues;
>                   curKey = pair._1();
>                   curValues = new ArrayList<BytesWritable>();
>                   curValues.add(pair._2());
>                   return new Tuple2<HiveKey, Iterable<BytesWritable>>(key,
values);
>                 }
>                 curKey = pair._1();
>                 curValues.add(pair._2());
>               }
>               if (curKey == null) {
>                 throw new NoSuchElementException();
>               }
>               // if we get here, this should be the last element we have
>               HiveKey key = curKey;
>               curKey = null;
>               return new Tuple2<HiveKey, Iterable<BytesWritable>>(key, curValues);
>             }
> {code}
> Since the output from sortByKey is already sorted on key, it's possible to backup the
value iterable using the same input iterator.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message