Re: Parallel INSERT (INTO ... SELECT ...)

On Thu, Sep 24, 2020 at 12:38 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> I have not checked the patch but I guess if we parallelise Inserts
> with Returning then isn't it better to have Gather node above Parallel
> Inserts?
>

This is indeed the case with the patch applied.

For example:

test=# explain insert into primary_tbl select * from third_tbl
returning index, height;
QUERY PLAN
-----------------------------------------------------------------------------------
Gather (cost=0.00..28.15 rows=9999 width=12)
Workers Planned: 3
-> Parallel Insert on primary_tbl (cost=0.00..28.15 rows=1040 width=12)
-> Parallel Seq Scan on third_tbl (cost=0.00..87.25
rows=3225 width=12)
(4 rows)

test=# insert into primary_tbl select * from third_tbl returning index, height;
index | height
-------+--------
1 | 1.2
2 | 1.2
3 | 1.2
4 | 1.2
5 | 1.2
6 | 1.2
7 | 1.2

...

9435 | 1.2
9619 | 1.2
9620 | 1.2
(9999 rows)

INSERT 0 9999

Regards,
Greg Nancarrow
Fujitsu Australia