(disclosure: I'm one of the founders at Citus Data)
hey, one way to do that is to use the MongoDB foreign data wrapper - also mentioned in some of the earlier threads.
mongo_fdw (https://github.com/citusdata/mongo_fdw) allows you to run SQL on MongoDB on a single node. Citus Data allows you to parallelize your SQL queries across multiple nodes (in this case, multiple MongoDB instances) by just syncing shard metadata. So you would effectively run SQL on a sharded mongo cluster without moving the data anywhere else.
another idea could be to use MoSQL to neatly replicate each mongo instance to a separate PostgreSQL instance, and then use Citus Data to run distributed SQL queries across the resulting PostgreSQL cluster.
hey, one way to do that is to use the MongoDB foreign data wrapper - also mentioned in some of the earlier threads.
mongo_fdw (https://github.com/citusdata/mongo_fdw) allows you to run SQL on MongoDB on a single node. Citus Data allows you to parallelize your SQL queries across multiple nodes (in this case, multiple MongoDB instances) by just syncing shard metadata. So you would effectively run SQL on a sharded mongo cluster without moving the data anywhere else.
another idea could be to use MoSQL to neatly replicate each mongo instance to a separate PostgreSQL instance, and then use Citus Data to run distributed SQL queries across the resulting PostgreSQL cluster.