Re: [HACKERS] Partition-wise aggregation/grouping

Hi Robert,

On Mon, Feb 26, 2018 at 8:03 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

>
> Committed after incorporating your other fixes and updating the
> optimizer README.
>

Thanks Robert.

Off-list Rajkumar has reported an issue. When we have enable_hashagg set to
false, and Gather Merge path is chosen, it ended-up in an error saying
"ERROR: Aggref found in non-Agg plan node".

I had a look over his provided testcase and observed that when we create a
Gather Merge path over a cheapest partial path by sorting it explicitly as
generate_gather_paths won't consider it, we accidentally used cheapest
partial path from the input_rel to create a Gather Merge; instead we need a
cheapest partial path from the partially_grouped_rel.

Attached fix_aggref_in_non-agg_error.patch fixing this.
test_for_aggref_in_non-agg_error.patch has a testcase reported by Rajkumar
which I have added in a aggregates.sql.

While doing so, I have observed few cleanup changes, added those in
misc_cleanup.patch.

---

While re-basing my partitionwise aggregate changes, I observed that when we
want to create partial aggregation paths for a child partition, we don't
need to add Gather or Gather Merge on top of it as we first want to append
them all and then want to stick a gather on it. So it will be better to
have that code part in a separate function so that we can call it from
required places.

I have attached patch (create_non_partial_paths.patch) for it including all
above fix.

Thanks

> --
> Robert Haas
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>

--
Jeevan Chalke
Technical Architect, Product Development
EnterpriseDB Corporation
The Enterprise PostgreSQL Company