mongo_fdw

Overview

Version

Install

You can install mongo_fdw directly. First, make sure the PGDG repository is added and enabled:

pig repo add pgdg -u          # Add PGDG repo and update cache

Install the extension using pig or apt/yum/dnf:

pig install mongo_fdw;          # Install for current active PG version

pig ext install -y mongo_fdw -v 18  # PG 18
pig ext install -y mongo_fdw -v 17  # PG 17
pig ext install -y mongo_fdw -v 16  # PG 16
pig ext install -y mongo_fdw -v 15  # PG 15
pig ext install -y mongo_fdw -v 14  # PG 14

dnf install -y mongo_fdw_18       # PG 18
dnf install -y mongo_fdw_17       # PG 17
dnf install -y mongo_fdw_16       # PG 16
dnf install -y mongo_fdw_15       # PG 15
dnf install -y mongo_fdw_14       # PG 14

apt install -y postgresql-18-mongo-fdw   # PG 18
apt install -y postgresql-17-mongo-fdw   # PG 17
apt install -y postgresql-16-mongo-fdw   # PG 16
apt install -y postgresql-15-mongo-fdw   # PG 15
apt install -y postgresql-14-mongo-fdw   # PG 14

Create Extension:

CREATE EXTENSION mongo_fdw;

Usage

Sources: README, REL-5_5_3 release

Create Server

CREATE EXTENSION mongo_fdw;

CREATE SERVER mongo_server FOREIGN DATA WRAPPER mongo_fdw
  OPTIONS (address '127.0.0.1', port '27017');

Server Options: address (default 127.0.0.1), port (default 27017), authentication_database, replica_set, read_preference (primary, secondary, primaryPreferred, secondaryPreferred, nearest), ssl (default false), pem_file, pem_pwd, ca_file, ca_dir, crl_file, weak_cert_validation, use_remote_estimate (default false), enable_join_pushdown (default true), enable_aggregate_pushdown (default true), enable_order_by_pushdown (default true).

Create User Mapping

CREATE USER MAPPING FOR pguser SERVER mongo_server
  OPTIONS (username 'mongouser', password 'mongopass');

Create Foreign Table

CREATE FOREIGN TABLE warehouse (
  _id name,
  warehouse_id int,
  warehouse_name text,
  warehouse_created timestamptz
)
SERVER mongo_server
OPTIONS (database 'mydb', collection 'warehouse');

Important: The first column must be _id of type name (MongoDB’s object identifier).

Table Options: database (default test), collection (defaults to table name), enable_join_pushdown, enable_aggregate_pushdown, enable_order_by_pushdown.

CRUD Operations

SELECT warehouse_id, warehouse_name FROM warehouse WHERE warehouse_id > 10;
INSERT INTO warehouse VALUES ('new_id', 100, 'New Warehouse', now());
UPDATE warehouse SET warehouse_name = 'Updated' WHERE warehouse_id = 100;
DELETE FROM warehouse WHERE warehouse_id = 100;

Pushdown Features

mongo_fdw pushes down WHERE clauses, joins between foreign tables on the same server, aggregate functions, ORDER BY, LIMIT, and OFFSET to MongoDB for efficient query execution. Use the mongo_fdw.enable_join_pushdown, mongo_fdw.enable_aggregate_pushdown, mongo_fdw.enable_order_by_pushdown, and mongo_fdw.log_remote_query GUCs when diagnosing remote plans.

Version Notes

mongo_fdw 5.5.3, released upstream as REL-5_5_3, adds PostgreSQL 18 support, updates bundled mongoc-driver and json-c libraries for MongoDB 8, adds the mongo_fdw.log_remote_query debug GUC, and fixes nested-field, WHERE, ORDER BY, and unsafe join-pushdown cases. Upstream dropped PostgreSQL 12 support in this line.

Notes

• BSON only supports UTF-8; ensure PostgreSQL database uses UTF-8 encoding
• Column names with uppercase letters or dots (for nested documents) require double-quoting
• PostgreSQL limits column names to 63 characters by default