Re: [HACKERS] Partition-wise aggregation/grouping

On Thu, Dec 14, 2017 at 4:01 PM, Ashutosh Bapat
<ashutosh.bapat@enterprisedb.com> wrote:
>
> +
> +EXPLAIN (COSTS OFF)
> +SELECT a FROM pagg_tab GROUP BY a ORDER BY 1;
> +                   QUERY PLAN
> +-------------------------------------------------
> + Group
> +   Group Key: pagg_tab_p1.a
> +   ->  Merge Append
> +         Sort Key: pagg_tab_p1.a
> +         ->  Group
> +               Group Key: pagg_tab_p1.a
> +               ->  Sort
> +                     Sort Key: pagg_tab_p1.a
> +                     ->  Seq Scan on pagg_tab_p1
> [ ... clipped ... ]
> +(19 rows)
>
> It's strange that we do not annotate partial grouping as Partial. Does not look
> like a bug in your patch. Do we get similar output with parallel grouping?

I am wrong here. It's not partial grouping. It's two level grouping. I
think annotating Group as Partial would be misleading. Sorry.


-- 
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company