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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-266) Improve SerDe performance by using Text instead of String
Date Fri, 03 Apr 2009 05:21:12 GMT

    [ https://issues.apache.org/jira/browse/HIVE-266?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12695243#action_12695243
] 

Zheng Shao commented on HIVE-266:
---------------------------------

A simple "INSERT SELECT *" shows with the pending changes (and HIVE-375, HIVE-356) we saved
23% or running time:
Both input and output tables are gzip-block-compressed sequence files. The saving could be
bigger for uncompressed tables.

{code}
task	new(sec)	old(sec)	ratio
0	137	183	0.74863388
1	135	173	0.780346821
2	131	172	0.761627907
3	127	165	0.76969697
4	136	180	0.755555556
5	142	170	0.835294118
6	128	170	0.752941176
7	133	177	0.751412429
8	143	173	0.826589595
9	126	178	0.707865169
total	1338	1741	0.768523837
{code}


> Improve SerDe performance by using Text instead of String
> ---------------------------------------------------------
>
>                 Key: HIVE-266
>                 URL: https://issues.apache.org/jira/browse/HIVE-266
>             Project: Hadoop Hive
>          Issue Type: Improvement
>          Components: Serializers/Deserializers
>    Affects Versions: 0.2.0
>            Reporter: Zheng Shao
>            Priority: Critical
>         Attachments: HIVE-266.1.patch
>
>
> A recent performance study showed that 2 places in Hive code has exhibited large cpu
usage percentage:
> 1. String.getBytes() (UTF-8 encoding)
> 2. String.split()
> We should replace String with Text object to:
> 1. Avoid UTF-8 decoding and encoding
> 2. Reuse the Text object and avoid creating new objects for each column in each row like
in String.split()
> This is expected to give a big (20%+) performance improvement to Hive.

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