Re: [HACKERS] utility commands benefiting from parallel plan

On Fri, Feb 24, 2017 at 11:43 AM, Haribabu Kommi
<kommi.haribabu@gmail.com> wrote:
> Here I attached an implementation patch that allows
> utility statements that have queries underneath such as
> CREATE TABLE AS, CREATE MATERIALIZED VIEW
> and REFRESH commands to benefit from parallel plan.
>
> These write operations not performed concurrently by the
> parallel workers, but the underlying query that is used by
> these operations are eligible for parallel plans.
>
> Currently the write operations are implemented for the
> tuple dest types DestIntoRel and DestTransientRel.
>
> Currently I am evaluating other write operations that can
> benefit with parallelism without side effects in enabling them.

The Idea looks good to me.

Since we are already modifying heap_prepare_insert, I am thinking that
we can as well enable queries like "insert into .. select from .."
with minor modification?

- * For now, parallel operations are required to be strictly read-only.
- * Unlike heap_update() and heap_delete(), an insert should never create a
- * combo CID, so it might be possible to relax this restriction, but not
- * without more thought and testing.
+ * For now, parallel operations are required to be strictly read-only in
+ * parallel worker.
This statement is still not true, we can not do heap_update in the
leader even though worker are doing the read-only operation (update
with select).  We can change the comments such that it appears more
specific to insert I think.
-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com