Indeed, that's confusing. You don't want to push down the count; the plan must execute "select distinct customer_id" separately on each shard, then merge the re

Indeed, that's confusing. You don't want to push down the count; the plan must execute "select distinct customer_id" separately on each shard, then merge the results and count. Not sure if that's what they really meant — since their business is sharding, this shouldn't be new to them.