Re: parallel distinct union and aggregate support patch

On 1/25/21 9:14 AM, bucoo@sohu.com wrote:
> Now, I rewrite batch hashagg and sort, add some comment and combin too 
> patches. base on master 2ad78a87f018260d4474eee63187e1cc73c9b976.
> They are support rescan and change GUC 
> enable_batch_hashagg/enable_batch_sort to 
> max_hashagg_batches/max_sort_batch, default value is "0"(mean is disable).
> The "max_hashagg_batches" in grouping sets each chain using this value, 
> maybe we need a better algorithm.
> Do not set "max_sort_batch" too large, because each tuplesort's work 
> memory is "work_mem/max_sort_batch".
> 
> Next step I want use batch sort add parallel merge join(thinks Dilip 
> Kumar) and except/intersect support after this patch commit, welcome to 
> discuss.

This patch has not gotten any review in the last two CFs and is unlikely 
to be committed for PG14 so I have moved it to the 2021-07 CF. A rebase 
is also required so marked Waiting for Author.

I can see this is a work in progress, but you may want to consider the 
several suggestions that an unbuffered approach might be better.

Regards,
-- 
-David
david@pgmasters.net