Re: [Postgres-xc-developers] SRF not working ?

[Pavan D. <pav...@gm...>]

On Fri, Jul 5, 2013 at 9:53 AM, Ashutosh Bapat <
ash...@en...> wrote:

>
>
>
> On Thu, Jul 4, 2013 at 6:50 PM, Michael Paquier <mic...@gm...
> > wrote:
>
>>
>>
>>
> I don't agree that it's because of immutability. It has more to do with
> the VALUES_RTE in INSERT statement. Any INSERT statement that is inserting
> more than one value in the distributed table can not be FQSed. In case
> there are more than one value being INSERTED through an INSERT statement,
> there are two RTEs in the query, one for the relation where INSERT is
> happening, and other for the values. So, I had implemented a simple rule in
> FQS shippability - if there are more than one RTEs in INSERT statement, do
> not FQS it. But I am unable to locate this rule now. Looks like while
> implementing something else, the rule has disappeared. And, since we do not
> have test for it, we didn't notice it.
>
>


You mean this code in pgxcship.c ?

 905
 906             /* PGXCTODO: It should be possible to look at the Query
and find out
 907              * whether it can be completely evaluated on the Datanode
just like SELECT
 908              * queries. But we need to be careful while finding out
the Datanodes to
 909              * execute the query on, esp. for the result relations. If
one happens to
 910              * remove/change this restriction, make sure you change
 911              * pgxc_FQS_get_relation_nodes appropriately.
 912              * For now DMLs with single rtable entry are candidates
for FQS
 913              */
 914             if (query->commandType != CMD_SELECT &&
list_length(query->rtable) > 1)
 915                 pgxc_set_shippability_reason(sc_context,
SS_UNSUPPORTED_EXPR);

BTW, I looked at the regression and I spotted at least one test case that
use generate_series() to insert data in a distributed table but still does
not fail. Its so because the test case uses a subquery to fire the insert.
So a workaround to the failing query is:

INSERT INTO testtbl SELECT generate_series(1,10000), 'foo';

Thanks,
Pavan
-- 
Pavan Deolasee
http://www.linkedin.com/in/pavandeolasee