To use mongo_fdw and mount Mongo collections, run:

$ sgr mount mongo_fdw example/mongo \
    -c username:password@mongo_host:27017 -o @- <<EOF
{
    "example_table": {
        "schema": {"column_1": "text", "column_2": "numeric"},
        "options": {"db": "example_db", "coll": "example_collection"}
    }
}
EOF

This will create a schema called example/mongo on your engine, mounting the MongoDB database from mongo_host:27017. The schema will contain one foreign table, example_table, that will contain documents from the collection example_collection in the database example_db. The table will have 2 columns, column_1 and column_2, populated from the documents in that collection.

Note that this doesn't actually ingest any data from the remote database: if you query this foreign table, the query will be converted to a MongoDB query behind the scenes and forwarded to the target database:

$ sgr sql -s example/mongo "SELECT * FROM example_table"

To snapshot the table, making it part of an actual Splitgraph image, use the sgr import command:

$ sgr import example/mongo \
    "SELECT column_1, column_2 FROM example_table" \
    example/mongo_repo example_table

example/mongo_repo:example_table has been imported from example/mongo:select column_1, column_2 from example_table

sgr import can also be used to import tables between Splitgraph repositories without consuming extra space. For more information, see the command line reference.