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https://issues.apache.org/jira/browse/HADOOP-1608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12540287
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stack commented on HADOOP-1608:
-------------------------------
Edward:
I do not understand what you mean by the following in your 02/Nov/07 06:09 PM
comment: "I'll implement relational algebra operators to the tentative language
and HQL by Sub-Tasks List sequence."
In org.apache.hadoop.hbase.shell.algebra, test for output table presence and
creation if missing is duplicated code in Selection, Projection,
DuplicateTable, etc. I tried to move this duplicated code back up into the
RelationalOperation class as a utility but noticed then if table already
exists, we don't call initJob because we return early (See end of the getConf
in DuplicateTable for example). Is running one of these operators a second
time, after table has been created, a problem? Have you tried it?
I did not have a mapreduce cluster running and so the last line hung for ever
(You should add to help need for a mapreduce cluster).
{code}
Hbase> aaa = table('y');
Hbase> aaa;
Syntax error : Type 'help;' for usage.Message : Encountered ";" at line 1,
column 5.
Hbase> show aaa;
Missing parameters. Please check 'Show' syntax
Hbase> bbb = group aaa by ('x'); Hbase> save bbb into table ('a');
{code}
Note, it would be nice if you entered a variable name only if you got a
description of the variable content or perhaps doing 'show VARIABLE_NAME'
output some kind of description.
I then started up a cluster and did the simplest of operations:
{code}
Hbase> aaa = table('x');
Hbase> save aaa into table(aaaaaa);
07/11/05 21:26:57 WARN mapred.JobClient: No job jar file set. User classes may
not be found. See JobConf(Class) or JobConf#setJar(String).Job
job_200711052125_0001 is still running........Job failed.
{code}
Job failed because of 'Caused by: java.lang.ClassNotFoundException:
org.apache.hadoop.hbase.mapred.TableSplit'. How do you run on a cluster
Edward? Do you copy the hbase jar into the hadoop lib dir all over the
cluster? Does HADOOP-1622 help here?
On job failure, should the table be removed? Currently, I have a new table
'aaaaaa' with nothing in it.
The output of Group, Selection, etc. is saved to an 'output' table?
It would be good if we could get into the help listing somewhere the operators
and types of conditions allowed on selection (>, <, AND, OR, etc.).
One last thing, hbase shell (relational) operators running mapreduce jobs
begins to impinge on PIG territory. We should be careful and avoid
overlap/duplicating work. Would it make sense doing further operators as PIG
user defined functions? (I suppose we'll be able to tell better after PIG-6,
the hbase load/store, is done. Smile).
Otherwise, patch looks good Edward.
> [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
>
>
> 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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