Re: [HACKERS] Gather Merge - Mailing list pgsql-hackers

 

 

On Fri, Mar 10, 2017 at 2:42 PM, Andreas Joseph Krogh <andreas@visena.com> wrote:

På fredag 10. mars 2017 kl. 10:09:22, skrev Rushabh Lathia <rushabh.lathia@gmail.com>:

 

 

On Fri, Mar 10, 2017 at 2:33 PM, Andreas Joseph Krogh <andreas@visena.com> wrote:

[...]

The execution-plan seems (unsurprisingly) to depend on data-distribution, so is there a way I can force a GatherMerge?

 

Not directly. GatherMerge cost is mainly depend on parallel_setup_cost,

parallel_tuple_cost and cpu_operator_cost. May be you can force this

by setting this cost low enough. Or another way to force is by disable the

other plans.

 

What plan you are getting now? You not seeing the below error ?

 

ERROR:  GatherMerge child's targetlist doesn't match GatherMerge

 

I'm seeing the same error, it's just that for reproducing it I'd rather not copy my whole dataset.

 

Can you share me a schema information, I will try to reproduce at my side?

drop table if EXISTS temp_email_address_owner;
drop table if EXISTS temp_email_delivery;
drop table if EXISTS temp_email_message;

create table temp_email_message(   entity_id BIGSERIAL PRIMARY KEY
);

create table temp_email_delivery(   entity_id BIGSERIAL PRIMARY KEY,   message_id bigint not null references temp_email_message(entity_id),   from_entity_id bigint,   received_timestamp timestamp not null
);

create table temp_email_address_owner(   entity_id BIGSERIAL PRIMARY KEY,   message_id bigint not null references temp_email_message(entity_id),   recipient_id bigint
);

EXPLAIN ANALYSE SELECT
                    em.entity_id               FROM temp_email_delivery del                   JOIN temp_email_message em ON (del.message_id = em.entity_id)               WHERE del.from_entity_id = 279519
                      OR
                      em.entity_id IN (                         SELECT
                              ea_owner.message_id                         FROM temp_email_address_owner ea_owner                         WHERE ea_owner.recipient_id = 279519
                      )               ORDER BY del.received_timestamp DESC
                LIMIT 101 OFFSET 0;