|From:||Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com>|
|To:||Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>|
|Cc:||Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>|
|Subject:||Re: Partition-wise aggregation/grouping|
|Views:||Raw Message | Whole Thread | Download mbox|
Thanks Ashutosh for reviewing.
Attached new patch-set with following changes:
1. Removed earlier 0007 and 0008 patches which were PoC for supporting
partial aggregation over fdw. I removed them as it will be a different
issue altogether and hence I will tackle them separately once this is
This patch-set now includes support for parallel plans within partitions.
Partition-wise Join Version: 34
(First six patches 0001 - 0006, remains the same functionality-wise)
0007 - Refactors partial grouping paths creation into the separate function.
0008 - Enables parallelism within the partition-wise aggregation.
This patch also includes a fix for the crash reported by Rajkumar.
While forcibly applying scan/join target to all the Paths for the scan/join
rel, earlier I was using apply_projection_to_path() which modifies the path
in-place which causing this crash as the path finally chosen has been
updated by partition-wise agg path creation. Now I have used
create_projection_path() like we do in partial aggregation paths.
Also, fixed issues reported by Ashutosh.
On Tue, Sep 26, 2017 at 6:16 PM, Ashutosh Bapat <
> Hi Jeevan,
> I have started reviewing these patches.
> 0001 looks fine. There might be some changes that will be needed, but
> those will be clear when I review the patch that uses this
> + *
> + * If targetlist is provided, we use it else use targetlist from the root.
> static double
> get_number_of_groups(PlannerInfo *root,
> double path_rows,
> - grouping_sets_data *gd)
> + grouping_sets_data *gd,
> + List *tlist)
> Query *parse = root->parse;
> double dNumGroups;
> + List *targetList = (tlist == NIL) ? parse->targetList : tlist;
> May be we should just pass targetlist always. Instead of passing NIL,
> pass parse->targetList directly. That would save us one conditional
> assignment. May be passing NIL is required for the patches that use
> this refactoring, but that's not clear as is in this patch.
Done in attached patch-set.
> In the documenation of enable_partition_wise_aggregate, we should
> probably explain why the default is off or like partition_wise_join
> GUC, explain the consequences of turning it off.
I have updated this. Please have a look.
> I doubt if we could
> accept something like partition_wise_agg_cost_factor looks. But we can
> discuss this at a later stage. Mean time it may be worthwhile to fix
> the reason why we would require this GUC. If the regular aggregation
> has cost lesser than partition-wise aggregation in most of the cases,
> then probably we need to fix the cost model.
Yep. I will have a look mean-while.
> I will continue reviewing rest of the patches.
Technical Architect, Product Development
The Enterprise PostgreSQL Company
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