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From "Gopal V (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-10163) CommonMergeJoinOperator calls WritableComparator.get() in the inner loop
Date Thu, 02 Apr 2015 07:03:53 GMT

     [ https://issues.apache.org/jira/browse/HIVE-10163?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Gopal V updated HIVE-10163:
---------------------------
    Attachment: HIVE-10163.2.patch

[~hagleitn]: The thread locking disappeared with your patch, but I found the Hashmap in a
few traces, which is pointless when maxAlias is bounded.

Also fixed the JIT performance for the 1-key JOIN clauses & cross-products.

> CommonMergeJoinOperator calls WritableComparator.get() in the inner loop
> ------------------------------------------------------------------------
>
>                 Key: HIVE-10163
>                 URL: https://issues.apache.org/jira/browse/HIVE-10163
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Processor
>    Affects Versions: 1.2.0
>            Reporter: Gopal V
>            Assignee: Gunther Hagleitner
>              Labels: JOIN, Performance
>         Attachments: HIVE-10163.1.patch, HIVE-10163.2.patch, mergejoin-comparekeys.png,
mergejoin-parallel-bt.png, mergejoin-parallel-lock.png
>
>
> The CommonMergeJoinOperator wastes CPU looking up the correct comparator for each WritableComparable
in each row.
> {code}
> @SuppressWarnings("rawtypes")
>   private int compareKeys(List<Object> k1, List<Object> k2) {
>     int ret = 0;
> ....   
>       ret = WritableComparator.get(key_1.getClass()).compare(key_1, key_2);
>       if (ret != 0) {
>         return ret;
>       }
>     }
> {code}
> !mergejoin-parallel-lock.png!
> !mergejoin-comparekeys.png!
> The slow part of that get() is deep within {{ReflectionUtils.setConf}}, where it tries
to use reflection to set the Comparator config for each row being compared.
> !mergejoin-parallel-bt.png!



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