RE: Determine parallel-safety of partition relations for Inserts

> Hi,
> 
> Attatching v1 patches, introducing options which let user manually control
> whether to use parallel dml.
> 
> About the patch:
> 1. add a new guc option: enable_parallel_dml (boolean) 2. add a new
> tableoption: parallel_dml (boolean)
> 
>    The default of both is off(false).
> 
> User can set enable_parallel_dml in postgresql.conf or seesion to enable
> parallel dml.
> If user want to choose some specific to use parallel insert, they can set
> table.parallel_dml to on.
> 
> Some attention：
> (1)
> Currently if guc option enable_parallel_dml is set to on but table's
> parallel_dml is off, planner still do not consider parallel for dml.
> 
> In this way, If user want to use parallel dml , they have to set
> enable_parallel_dml=on and set parallel_dml = on.
> If someone dislike this, I think we can also let tableoption. parallel_dml's
> default value to on ,with this user only need to set enable_parallel_dml=on
> 
> (2)
> For the parallel_dml.
> If target table is partitioned, and it's parallel_dml is set to on, planner
> will ignore The option value of it's child.
> This is beacause we can not divide dml plan to separate table, so we just
> check the target table itself.
> 
> 
> Thoughts and comments are welcome.

The patch is based on v13 patch(parallel insert select) in [1]

[1] https://www.postgresql.org/message-id/CAJcOf-ejV8iU%2BYpuV4qbYEY-2vCG1QF2g3Gxn%3DZ%2BPyUH_5f84A%40mail.gmail.com

Best regards,
houzj