On 15.11.2017 13:35, Jeevan Chalke wrote:
Obviously this check (aggtype==aggtranstype) is not correct criteria for all user defined aggregates.
I just did it as temporary work around for standard aggregates.
...
The main problem IMHO is that there are a lot of different threads and patches related with this topic:(
And it is very difficult to combine all of them together to achieve the final goal: efficient execution of OLAP queries on sharded table.
It will be nice if somebody who is making the most contribution in this direction can somehow maintain it...
I just faced with particular problem with our pg_shardman extension and now (thanks to your patch) I have some working solution for it.
But certainly I prefer to have this support in mainstream version of Postgres.
There are two open questions, which I wan to discuss (sorry, may be one again this is not the right thread for it):
1. Parallel append and FDW/postgres_fdw: should FDW support parallel scan and do we really need it to support concurrent execution of query on local and remote partitions?
"Asynchronous append" partly solves this problem, but only for remote partitions. I do not completely understand all complexity of alternative approaches.
2. Right now partition-wise aggregation/grouping works only for tables partitioned using new PG 10 partitioning mechanism. But it doesn't work for inherited tables, although
there seems to be not so much difference between this two cases. Do you think that sometimes it will be also supported for standard inheritance mechanism or there is no sense in it?
--
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
