Re: Parallel Inserts in CREATE TABLE AS - Mailing list pgsql-hackers

On Thu, Dec 10, 2020 at 3:59 PM Hou, Zhijie <houzj.fnst@cn.fujitsu.com> wrote:
>
> Hi
>
> +               allow = ps && IsA(ps, GatherState) && !ps->ps_ProjInfo &&
> +                               plannedstmt->parallelModeNeeded &&
> +                               plannedstmt->planTree &&
> +                               IsA(plannedstmt->planTree, Gather) &&
> +                               plannedstmt->planTree->lefttree &&
> +                               plannedstmt->planTree->lefttree->parallel_aware &&
> +                               plannedstmt->planTree->lefttree->parallel_safe;
>
> I noticed it check both IsA(ps, GatherState) and IsA(plannedstmt->planTree, Gather).
> Does it mean it is possible that IsA(ps, GatherState) is true but IsA(plannedstmt->planTree, Gather) is false ?
>
> I did some test but did not find a case like that.
>

This seems like an extra check.  Apart from that if we combine 0001
and 0002 there should be an additional protection so that it should
not happen that in cost_gather we have ignored the parallel tuple cost
and now we are rejecting the parallel insert. Probably we should add
an assert.


-- 
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com