One of the most interesting Postgres projects I have seen in many years.
The benchmarks presented only seem to address standard pooling, I'd like to see what it looks like once query parsing and cross-shard join come into play.
Thank you! Good feedback. The query parser is cached, so if you're using prepared statements or just the extended protocol with placeholders, it's almost free: cost of a mutex + hash lookup.
Cross-shard joins will be interesting. I suspect the biggest cost there will be executing suboptimal queries without a good join filter: that's what it takes to compute a correct result sometimes. Also, the result set could get quite large, so we may need to page to disk.
I'm focusing on OLTP use cases first with joins pushed down as much as possible. I suspect cross-shard joins will be requested soon afterwards.