Re: [Postgres-xc-developers] Data distribution by hash - general question

[Mason S. <ma...@st...>]

On Tue, Jul 16, 2013 at 9:30 AM, Adam Dec <ada...@gm...> wrote:

> Yes A is like a parent and all the others are like a children (joined with
> foreign key)...so using parent primary key (id) I will be sure that the
> data (that are joined) will all stay at the same node? What about the
> situation when table B is also joined (using foreign key) with some other
> table? Is that the same?
>
>
If B is distributed on id but also contains column "id2" that is joined
with table E, then it can only push down some of the joins. It will end up
needing to join on one single coordinator and shipping all of the data
there (This is one of the issues that StormDB addresses in our version).



>
> 2013/7/16 Mason Sharp <ma...@st...>
>
>> Adam,
>>
>> Is "id" present in all of A,B,C, and D? Is A the parent and the other
>> children and used as a foreign key from B,C, and D to A? If so, yes, on the
>> surface it sounds like you can do that and be able to take advantage of
>> pushing down joins to the local data nodes.
>>
>> Regards,
>>
>> Mason
>>
>>
>> On Mon, Jul 15, 2013 at 9:03 AM, Adam Dec <ada...@gm...> wrote:
>>
>>> Hi!
>>>
>>> My topology: 2 machines (on each machine 1 master coordinator and 1
>>> master datannode)
>>>
>>> Lets say that I have a table A which has
>>> - one-to-many relation with table B
>>> - one-to-many relation to table C
>>> - one-to-one relation with table D
>>>
>>> I would like to distribute it in the cluster. All I have to do is to put
>>> DISTRIBUTE BY HASH(id); in each of the tables while creating them?
>>> id - primary key
>>>
>>> In my example Table A is like a root of the graph. How to create such a
>>> "graph of tables" to be shure
>>> that when I will invoke a select with joins all the proceesin will be
>>> done only on the one node.
>>> I do not want to replicate all the data.
>>>
>>> Where can I read about data distribution in Postgres XC? Do you have any
>>> examples that I could look at?
>>>
>>>
>>> Regards,
>>>
>>> Adam Dec
>>>
>>>
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>>>
>>
>>
>> --
>> Mason Sharp
>>
>> StormDB - http://www.stormdb.com
>> The Database Cloud
>> Postgres-XC Support and Services
>>
>
>


-- 
Mason Sharp

StormDB - http://www.stormdb.com
The Database Cloud
Postgres-XC Support and Services