Theta joins don't do we'll in any system.
Are both tables large?
If not its a map side join and the reducer will be just an ordinary reducer(s).
Sent from a remote device. Please excuse any typos...
Mike Segel
On Apr 11, 2013, at 12:18 AM, Vikas Jadhav vikascjadha...@gmail.com wrote:
I wil
Can you show an example of your join?
All joins are an equality in that the key has to match.
Whether its a one to one , one to many, or many to many remains to be seen.
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Mike Segel
On Apr 9, 2013, at 10:35 AM, Effyroth Gu effyr...@gmail.com
How are you going to support NON EQUI Join using MapReduce ?
As per my understanding there is only one way to do this is
to bring all data to one reducer then reducer will know lesser/greater
values correctly.
Correct me if I am wrong.
Thank You.
* Regards,*
* Vikas *
On Wed, Apr 10, 2013 at
I wil express it in SQL form
select * from table1, table2 where table1.attr table2.attr
it is also called theta join where theta can be , , =,=,!=
On Wed, Apr 10, 2013 at 9:35 PM, Michel Segel michael_se...@hotmail.comwrote:
Not sure what is meant by a non equi join.
Are you saying
Hi,
Your cross join is supported in both pig and hive. (Cross, and Theta joins)
So there must be code to do this.
Essentially in the reducer you would have your key and then the set of rows
that match the key. You would then perform the cross product on the key's
result set and output them
Only equality joins, outer joins, and left semi joins are supported in
Hive. Hive does not support join conditions that are not equality
conditions as it is very difficult to express such conditions as a
map/reduce job. Also, more than two tables can be joined in Hive.
2013/4/9 Michael Segel
Hi
I am also woring on join using MapReduce
i think instead of finding postion of table in RawKeyValuIterator.
what we can do modify context.write method to alway write key as table name
or id
then we dont need to find postion we can get Key and Value from
reducerContext
befor calling
In reduce() we have:
key1 values1
key2 values2
...
keyn valuesn
so,what i want to do is join all values like a SQL:
select * from values1,values2...valuesn;
if memory is not enough to cache values,how to complete the join operation?
my idea is clone the reducecontext,but it maybe not easy.
you want a n:n join or 1:n join?
On Mar 13, 2013 10:51 AM, Roth Effy effyr...@gmail.com wrote:
I want to join two table data in reducer.So I need to find the start of
the table.
someone said the DataJoinReducerBase can help me,isn't it?
2013/3/13 Azuryy Yu azury...@gmail.com
you cannot
I want a n:n join as Cartesian product,but the DataJoinReducerBase looks
like only support equal join.
I want a non-equal join,but I have no idea now.
2013/3/13 Azuryy Yu azury...@gmail.com
you want a n:n join or 1:n join?
On Mar 13, 2013 10:51 AM, Roth Effy effyr...@gmail.com wrote:
I want
Hi,everyone,
I want to join the k-v pairs in Reduce(),but how to get the record position?
Now,what I thought is to save the context status,but class Context doesn't
implement a clone construct method.
Any help will be appreciated.
Thank you very much.
Through the RecordReader and FileStatus you can get it.
On Tue, Mar 12, 2013 at 4:08 PM, Roth Effy effyr...@gmail.com wrote:
Hi,everyone,
I want to join the k-v pairs in Reduce(),but how to get the record
position?
Now,what I thought is to save the context status,but class Context doesn't
sorry，I still can't understand how to use recordreader in the
reduce(),because the input is a RawKeyValueIterator in the class
reducecontext.so,I'm confused.
anyway,thank you.
2013/3/12 samir das mohapatra samir.help...@gmail.com
Through the RecordReader and FileStatus you can get it.
On
I want to join two table data in reducer.So I need to find the start of the
table.
someone said the DataJoinReducerBase can help me,isn't it?
2013/3/13 Azuryy Yu azury...@gmail.com
you cannot use RecordReader in Reducer.
what's the mean of you want get the record position? I cannot
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