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Hive, mail # dev - Re: [jira] [Commented] (HIVE-2361) Add some UDFs which help to migrate Oracle to Hive


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Re: [jira] [Commented] (HIVE-2361) Add some UDFs which help to migrate Oracle to Hive
Lefty Leverenz 2013-02-14, 08:41
Here you go:

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– Lefty

On Thu, Feb 14, 2013 at 12:22 AM, neelesh gadhia (JIRA) <[EMAIL PROTECTED]>wrote:

>
>     [
> https://issues.apache.org/jira/browse/HIVE-2361?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13578222#comment-13578222]
>
> neelesh gadhia commented on HIVE-2361:
> --------------------------------------
>
> can you post the url for discussion/forum for  hive-user mailing list?. or
> is it just the email address I need to send the details about the issue?
>
> >  Add some UDFs which help to migrate Oracle to Hive
> > ---------------------------------------------------
> >
> >                 Key: HIVE-2361
> >                 URL: https://issues.apache.org/jira/browse/HIVE-2361
> >             Project: Hive
> >          Issue Type: New Feature
> >          Components: UDF
> >    Affects Versions: 0.8.0
> >            Reporter: JunHo Cho
> >            Assignee: JunHo Cho
> >            Priority: Minor
> >              Labels: features
> >         Attachments: nexr-udf.tar
> >
> >
> > Here some UDFs which can be matched to oracle functions:
> > There are two kinds of oracle functions. one is scalar function and
> another is analytic function.
> > Most scalar functions in Oracle can be converted to hive's udf directly.
> > Oracle Scalar Function
> > GenericUDFDecode : Compares first argument to each other value one by
> one. e.g., DECODE(x,0,'zero',1,'one') will return 'zero' if x is 0
> > GenericUDFGreatest : Return the greatest of the list of one or more
> expressions. e.g., GREATEST(2,5,12,3) will return 12
> > GenericUDFInstr : Return the location of a substring in a string. e.g.,
> INSTR('next', 'e') will return 2
> > GenericUDFLnnvl : Evaluate a condition when one or both operands of the
> condition may be null. e.g., LNNVL(2 > 4) will return true
> > GenericUDFNVL : Replace null with a string in the results of a query.
> e.g., NVL(null,'hive') will return hive
> > GenericUDFNVL2 : Determine the value returned by a query based on
> whether a specified expression is null or not null. e.g., NVL2(null,'not
> null','null value') will return 'null value'
> > GenericUDFToNumber : Convert a string to a number. e.g.,
> TO_NUMBER('112','999') will return 112
> > GenericUDFTrunc : Returns a date truncated to a specific unit of
> measure. e.g., TRUNC('2002-11-02 01:01:01','YYYY') will return '2002-01-01
> 00:00:00'
> > Oracle Analytic Function
> > Most analytic functions in Oracle can't be converted to hive's query and
> udf directly.
> > Following udfs should be used with DISTRIBUTED, SORT BY and HASH of hive
> to support analytic functions
> > e.q., SELECT _FUNC_(hash(col1), col2, ...) FROM SELECT ~ FROM table
> DISTRIBUTED BY hash(col1) SORT BY col1, col2 ...
> > GenericUDFSum : Calculate a cumulative sum.
> > GenericUDFRank : Assign a sequential order, or rank within some group
> based on key.
> > GenericUDFDenseRank : Act like RANK function except that it assigns
> consecutive ranks.
> > GenericUDFRowNumber : Return sequence integer value within some group
> based on key.
> > GenericUDFMax : Determine the highest value within some group based on
> key.
> > GenericUDFMin : Determine the lowest value within some group based on
> key.
> > GenericUDFLag : Access data from a previous row.
> > This udfs was developed with hive-pdk
>
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