Importing SQL from PostgreSQL and MongoDB documents

[#1]

Hi, 

I have a requirement where the final destination to have the data in the Cloudera data warehouse and then connect to the Tableau dashboard.
My data sources are PostgreSQL and MongoDB .

1. What would be the best way to ingest data from MongoDB, the document structure is very dynamic- with nested loops and different objects .
2. Do I convert the MongoDB documents to relational and then import the data or Have the documents imported as is from Mongo DB directly ?
3. Would I be able to query the unstructured data if imported as is ? 

Any help would be highly appreciated.