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

[Adam D. <ada...@gm...>]

So the very basic strategy for data distribution (as I understand it right
now) is to distribute data by hash (table with a lot of writes) using
primary key? Are there any other strategies/scenarios?


2013/7/16 Mason Sharp <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
>