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Date: Wed, 21 Nov 2007 23:37:43 -0800 (PST)
From: "stack (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-1608) [Hbase Shell] Relational Algrebra
 Operators
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    [ https://issues.apache.org/jira/browse/HADOOP-1608?page=3Dcom.atlassia=
n.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12544716 ]=20

stack commented on HADOOP-1608:
-------------------------------

Here's a few comments on latest Edward:

+ Exceptions are suppressed in maps and configurations.  They are just prin=
ted 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 ex=
ceptions are not allowed.   When you have a ParseException but you're only =
allowed throw ParseException, and the map task should fail, create an IOE o=
ut of the PE and throw that.
+ Also:

[23:06]=09<st^ack>=09edward: When I do SAVE A INTO table('table_name');
[23:06]=09<st^ack>=09what column does it go into?

+ 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?

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

I took the patch for a run... things seem to basically work.  Good stuff.

> [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=20
>            Reporter: Edward Yoon
>            Priority: Minor
>             Fix For: 0.16.0
>
>         Attachments: patch_v01.txt, patch_v02.txt, patch_v03.txt, patch_v=
04.txt, patch_v05.txt, patch_v06.txt, patch_v07.txt, patch_v08.txt, patch_v=
09.txt, patch_v10.txt, patch_v11.txt, patch_v12.txt, patch_v13.txt, patch_v=
14.txt, patch_v15.txt, patch_v16.txt, patch_v17.txt, patch_v18.txt, patch_v=
19.txt
>
>
> Development of relational algebra operators has begun.
>  * Projection=20
>   ** selects a subset of the columnfamilies of a relation =20
>   ** Result =3D =CF=80 ~column_list~ (Relation)=20
> {code}
> Hbase > Result =3D Relation.Projection('year','legnth');
> Hbase > save Result into table('result');
> {code}
>  * Selection
>   ** See : HADOOP-2003 issue's description
> {code}
> Hbase > Result =3D Relation.Selection(length > 100 and studioName =3D 'Fo=
x');=20
> Hbase > save Result into table('result');
> {code}
>  * Group
>   ** more details about 'GROUP' operation will be handled in HADOOP-1658 =
issue.=20
>  * =CE=B8 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=3Dn+m and attributes (A ~1~,A ~2~,=
...,A ~n~, B ~1~,B ~2~,...,B ~m~) that satisfy the join condition
> {code}
> Hbase > R1 =3D table('movieLog_table');
> Hbase > R2 =3D table('personInfo_table');
> Hbase > Result =3D R1.join(R1.producer: =3D R2.ROW) and R2;=20
>      or Result =3D R1.join(R1.actor:hero =3D R2.Row) and R2;
>      or Result =3D R1.join(R1.actor:hero =3D R2.Row and R1.studioName =3D=
 'Fox' and R2.occupation =3D 'singer') and R2;
> {code}

--=20
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