Re: Ordered Partitioned Table Scans

On Wed, 27 Mar 2019 at 19:48, Amit Langote
<Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> Sorry if this was discussed before, but why does this patch add any new
> code to partprune.c? AFAICT, there's no functionality changes to the
> pruning code.

You're right. It probably shouldn't be there. There's a bit of a lack
of a good home for partition code relating to the planner it seems.

> seem like their logic is specialized enough to be confined to pathkeys.c,
> only because it's needed there.

Yeah maybe.

> Regarding
>
> +bool
> +partitions_are_ordered(PlannerInfo *root, RelOptInfo *partrel)
>
> I think this could simply be:
>
> bool
> partitions_are_ordered(PartitionBoundInfo *boundinfo)
>
> and be defined in partitioning/partbounds.c. If you think any future
> modifications to this will require access to the partition key info in
> PartitionScheme, maybe the following is fine:
>
> bool
> partitions_are_ordered(RelOptInfo *partrel)

It does need to know how many partitions the partitioned table has,
which it gets from partrel->nparts, so yeah, RelOptInfo is probably
needed. I don't think passing in int nparts is a good solution to
that. The problem with moving it to partbounds.c is that nothing
there knows about RelOptInfo currently.

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