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From "Edward Yoon (JIRA)" <j...@apache.org>
Subject [jira] Issue Comment Edited: (HADOOP-1608) [Hbase Shell] Relational Algrebra Operators
Date Thu, 22 Nov 2007 10:51:43 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12544733
] 

udanax edited comment on HADOOP-1608 at 11/22/07 2:50 AM:
---------------------------------------------------------------

>> Exceptions are suppressed in maps and configurations. They are just printed on stderr,
which is better than nothing, but jobs should fail. Create a Runtime exception from the checked
exception so you can throw it where exceptions are not allowed. When you have a ParseException
but you're only allowed throw ParseException, and the map task should fail, create an IOE
out of the PE and throw that.

OK.

>> The GROUP help says this: "Group rows by value of an attribute and apply aggregate
function independently to each group of rows"... but I do not see an 'aggregate function'
in the example given. Am I missing something?

More details about 'GROUP' operation will be handled in HADOOP-1658 issue. 
If you want, i'll drop it from the hadoop-1608.
But, i'd like to submit some classes for group to svn tree.

So, i'll change only "group help" content.

>> The SAVE command wants to run a mapreduce job to copy into result table. Should say
it runs a MR job in help.

OK.



      was (Author: udanax):
    >> Exceptions are suppressed in maps and configurations. They are just printed on
stderr, which is better than nothing, but jobs should fail. Create a Runtime exception from
the checked exception so you can throw it where exceptions are not allowed. When you have
a ParseException but you're only allowed throw ParseException, and the map task should fail,
create an IOE out of the PE and throw that.

OK.

>> The GROUP help says this: "Group rows by value of an attribute and apply aggregate
function independently to each group of rows"... but I do not see an 'aggregate function'
in the example given. Am I missing something?

More details about 'GROUP' operation will be handled in HADOOP-1658 issue. 
If you want, i'll drop it from the hadoop-1608.
But, i'd like to submit some classes for group to svn tree.

>> The SAVE command wants to run a mapreduce job to copy into result table. Should say
it runs a MR job in help.

OK.


  
> [Hbase Shell] Relational Algrebra Operators
> -------------------------------------------
>
>                 Key: HADOOP-1608
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1608
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: contrib/hbase
>    Affects Versions: 0.14.1
>         Environment: All environments 
>            Reporter: Edward Yoon
>            Priority: Minor
>             Fix For: 0.16.0
>
>         Attachments: patch_v01.txt, patch_v02.txt, patch_v03.txt, patch_v04.txt, patch_v05.txt,
patch_v06.txt, patch_v07.txt, patch_v08.txt, patch_v09.txt, patch_v10.txt, patch_v11.txt,
patch_v12.txt, patch_v13.txt, patch_v14.txt, patch_v15.txt, patch_v16.txt, patch_v17.txt,
patch_v18.txt, patch_v19.txt
>
>
> Development of relational algebra operators has begun.
>  * Projection 
>   ** selects a subset of the columnfamilies of a relation  
>   ** Result = π ~column_list~ (Relation) 
> {code}
> Hbase > Result = Relation.Projection('year','legnth');
> Hbase > save Result into table('result');
> {code}
>  * Selection
>   ** See : HADOOP-2003 issue's description
> {code}
> Hbase > Result = Relation.Selection(length > 100 and studioName = 'Fox'); 
> Hbase > save Result into table('result');
> {code}
>  * Group
>   ** more details about 'GROUP' operation will be handled in HADOOP-1658 issue. 
>  * θ Join
>  ** The join of two relations R1(A ~1~,A ~2~,...,A ~n~) and R2(B ~1~,B ~2~,...,B ~m~)
is a relation with degree k=n+m and attributes (A ~1~,A ~2~,...,A ~n~, B ~1~,B ~2~,...,B ~m~)
that satisfy the join condition
> {code}
> Hbase > R1 = table('movieLog_table');
> Hbase > R2 = table('personInfo_table');
> Hbase > Result = R1.join(R1.producer: = R2.ROW) and R2; 
>      or Result = R1.join(R1.actor:hero = R2.Row) and R2;
>      or Result = R1.join(R1.actor:hero = R2.Row and R1.studioName = 'Fox' and R2.occupation
= 'singer') and R2;
> {code}

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