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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Created: (HIVE-664) optimize UDF split
Date Tue, 21 Jul 2009 17:56:14 GMT
optimize UDF split
------------------

                 Key: HIVE-664
                 URL: https://issues.apache.org/jira/browse/HIVE-664
             Project: Hadoop Hive
          Issue Type: Bug
          Components: Query Processor
            Reporter: Namit Jain


Min Zhou added a comment - 21/Jul/09 07:34 AM
It's very useful for us .
some comments:

   1. Can you implement it directly with Text ? Avoiding string decoding and encoding would
be faster. Of course that trick may lead to another problem, as String.split uses a regular
expression for splitting.
   2. getDisplayString() always return a string in lowercase.

[ Show » ]
Min Zhou added a comment - 21/Jul/09 07:34 AM It's very useful for us . some comments:

   1. Can you implement it directly with Text ? Avoiding string decoding and encoding would
be faster. Of course that trick may lead to another problem, as String.split uses a regular
expression for splitting.
   2. getDisplayString() always return a string in lowercase.


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Namit Jain added a comment - 21/Jul/09 09:22 AM
Committed. Thanks Emil
[ Show » ]
Namit Jain added a comment - 21/Jul/09 09:22 AM Committed. Thanks Emil

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Emil Ibrishimov added a comment - 21/Jul/09 10:48 AM
There are some easy (compromise) ways to optimize split:

1. Check if the regex argument actually contains some "regex specific characters" and if it
doesn't, do a straightforward split without converting to strings.
2. Assume some default value for the second argument (for example - split(str) to be equivalent
to split(str, ' ') and optimize for this value
3. Have two separate split functions - one that does regex and one that splits around plain
text.

I think that 1 is a good choice and can be done rather quickly.
[ Show » ]
Emil Ibrishimov added a comment - 21/Jul/09 10:48 AM There are some easy (compromise) ways
to optimize split: 1. Check if the regex argument actually contains some "regex specific characters"
and if it doesn't, do a straightforward split without converting to strings. 2. Assume some
default value for the second argument (for example - split(str) to be equivalent to split(str,
' ') and optimize for this value 3. Have two separate split functions - one that does regex
and one that splits around plain text. I think that 1 is a good choice and can be done rather
quickly.


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