Would this not be better done as a FDW?

[ollym]

I haven't delved too deep into the code, but I was wondering why you couldn't accomplish the same thing by writing a foreign data wrapper for MongoDB?

See: http://wiki.postgresql.org/wiki/Foreign_data_wrappers

[nelhage]

The folks at Citus Data have actually already written that FDW, which I experiment with before writing MoSQL: https://github.com/citusdata/mongo_fdw

MoSQL has several advantages, including:

• By pulling all the data into local storage, JOINs can be much more performant, since postgres has more ability to reason about and optimize them.
• By copying data into a secondary store for analytics, we can isolate background analytics and reporting from having any impact on production systems.

[ollym]

Would it not be better to improve the FDW driver? Since Postgres 9.3 you can now send updates via the FDW as-well. I wouldn't know about the efficiency of JOINs etc. but it looks like this is postgres' way forward

[nelhage]

If you want to improve the FDW and find that works better for your application, great! We've found that MoSQL works great for our use case, and believe that the model has several fundamental advantages, including performance of queries and aggregates, isolation from production, and the ability to write code in something other than C.