On Thu, Oct 22, 2020 at 5:08 AM Dilip Kumar <dilipbal...@gmail.com> wrote: > Interesting idea. So IIUC, whenever a worker is scanning the tuple it > will directly put it into the respective batch(shared tuple store), > based on the hash on grouping column and once all the workers are > doing preparing the batch then each worker will pick those baches one > by one, perform sort and finish the aggregation. I think there is a > scope of improvement that instead of directly putting the tuple to the > batch what if the worker does the partial aggregations and then it > places the partially aggregated rows in the shared tuple store based > on the hash value and then the worker can pick the batch by batch. By > doing this way, we can avoid doing large sorts. And then this > approach can also be used with the hash aggregate, I mean the > partially aggregated data by the hash aggregate can be put into the > respective batch.
I am not sure if this would be a win if the typical group size is small and the transition state has to be serialized/deserialized. Possibly we need multiple strategies, but I guess we'd have to test performance to be sure. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
