On Tue, Jun 23, 2015 at 5:07 AM, Rui Hai Jiang <ruihaiji...@msn.com> wrote:
> I'm trying to figure out how a query and its result is passed between a
> coordinator and a datanode. I know there are many messages passed between
> them to finish a query.
>
>
> I did a test against the coordinator by adding a row to a table and the sql
> was, insert into hg1(id, name) values(1,'tom').
>
> I found a command 'P' was sent from the coordinator to a datanode and there
> was a remote statement as following,
>
>
> stmt_name=p_1_25af_f
> query_string=Remote Subplan
> plan_string={REMOTESTMT :commandType 3 :hasReturning false ...}
>
>
> My questions are,
> 1-does the coordinator use the remote statement to tell a datanode what to
> do? If so, how is the plan string created by the coordinator and how is the
> plan_string parsed by the datanode?
>
> 2-if there are multiple rows in the result of the query, how are the rows of
> data passed from the datanode to the coordinator? Does the datanode just send
> all the rows of data to the coordinator? or the coordinator get each row of
> data by sending a query?
>
>
> Thank you very much!
This is probably an appropriate question for postgres-xl-developers,
but not pgsql-hackers. Those concepts do not exist in PostgreSQL,
only Postgres-XC or one of its proliferating set of forks.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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