| From: | Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> |
|---|---|
| To: | Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com> |
| Cc: | Dilip Kumar <dilipbalaut(at)gmail(dot)com>, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Robert Haas <robertmhaas(at)gmail(dot)com> |
| Subject: | Re: [HACKERS] Partition-wise aggregation/grouping |
| Date: | 2017-12-15 05:51:03 |
| Message-ID: | CAFjFpRe4V7YxpOHnqs6DOUKLigbpAYY0_1zE_6EmP9qcf_BujQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Dec 14, 2017 at 4:01 PM, Ashutosh Bapat
<ashutosh(dot)bapat(at)enterprisedb(dot)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
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