MongoDB Data Connector

MongoDB is an open-source NoSQL database that stores data in flexible, JSON-like documents, supporting dynamic schemas and easy scalability.

The MongoDB Data Connector enables federated/accelerated SQL queries on data stored in MongoDB databases.

datasets:
  - from: mongodb:mytable
    name: my_dataset
    params:
      mongodb_host: localhost
      mongodb_port: 27017
      mongodb_db: my_database
      mongodb_user: my_user
      mongodb_pass: ${secrets:mongodb_pass}
      mongodb_pool_min: 1
      mongodb_pool_max: 10

Configuration

from

The from field takes the form mongodb:{table_name} where table_name is the table identifer in the MongoDB server to read from.

info

Unquoted identifiers are normalized to lowercase. To reference a collection with mixed-case characters, wrap it in double quotes: mongodb:"MixedCaseCollection". See Identifier Case Sensitivity.

datasets:
  - from: mongodb:mytable
    name: my_dataset
    params:
      mongodb_db: my_database
      ...

name

The dataset name. This will be used as the table name within Spice.

Example:

datasets:
  - from: mongodb:my_dataset
    name: cool_dataset
    params: ...

SELECT COUNT(*) FROM cool_dataset;

+----------+
| count(*) |
+----------+
| 6001215  |
+----------+

The dataset name cannot be a reserved keyword

params

The MongoDB data connector can be configured by providing the following params. Use the secret replacement syntax to load the secret from a secret store, e.g. ${secrets:my_mongodb_conn_string}.

Parameter Name	Description
mongodb_connection_string	The connection string to use to connect to the MongoDB server. This can be used instead of providing individual connection parameters.
mongodb_user	The MongoDB username.
mongodb_pass	The password to connect with.
mongodb_host	The hostname of the MongoDB server. Defaults to localhost.
mongodb_port	The port of the MongoDB server. Defaults to 27017.
mongodb_db	The name of the database to connect to. Defaults to default.
mongodb_sslmode	Optional. Specifies the SSL/TLS behavior for the connection, supported values: required: (default) This mode requires an SSL connection. If a secure connection cannot be established, server will not connect. preferred: This mode will try to establish a secure SSL connection if possible, but will connect insecurely if the server does not support SSL. disabled: This mode will not attempt to use an SSL connection, even if the server supports it.
mongodb_sslrootcert	Optional parameter specifying the path to a custom PEM certificate that the connector will trust.
mongodb_time_zone	Optional. Specifies connection time zone. Default is UTC. Accepts: Fixed offsets (e.g., +02:00). IANA time zone names (e.g., America/Los_Angeles)
mongodb_auth_source	Optional. Authentication source database. Overrides the default auth source in the connection string.
mongodb_direct_connection	Optional. Whether to connect directly to a single MongoDB host instead of discovering the topology. Accepts true or false.
mongodb_srv	Optional. Use the mongodb+srv:// connection scheme for DNS SRV record discovery (MongoDB Atlas). Auto-detected (and mongodb_port is ignored) when mongodb_host ends with .mongodb.net. Accepts true or false. Default: false.
mongodb_unnest_depth	Optional. Maximum nesting depth for unnesting embedded documents into a flattened structure. Higher values expand deeper nested fields. Default: 0
mongodb_num_docs_to_infer_schema	Optional. Number of documents to use to infer the schema. Defaults to 400.
mongodb_pool_min	The minimum number of connections to keep open in the pool, lazily created when requested. Default: 1
mongodb_pool_max	The maximum number of connections to allow in the pool. Default: 5
mongodb_resume_token_invalid_behavior	Optional. Used with refresh_mode: changes. Behavior when a persisted Change Stream resume token is rejected by the server (e.g. it is past the oplog window). error (default) surfaces a clear error; rebootstrap drops the persisted token and re-snapshots the collection. See Using MongoDB Change Streams.
change_stream_batch_max_size	Optional. Used with refresh_mode: changes. Maximum number of Change Stream events grouped into one CDC batch before applying it. Default: 1000.
change_stream_batch_max_duration	Optional. Used with refresh_mode: changes. Maximum time to wait for a Change Stream batch to fill before applying it. Accepts fundu duration strings. Default: 1s.
change_stream_max_await_time	Optional. Used with refresh_mode: changes. Maximum time MongoDB waits for new Change Stream events before returning an empty server batch. Accepts fundu duration strings. Default: 1s.
change_stream_batch_size	Optional. Used with refresh_mode: changes. Number of Change Stream events MongoDB should request from the server per batch. Default: 1000.

Types

The table below shows the MongoDB data types supported, along with the type mapping to Apache Arrow types in Spice.

MongoDB Type	Arrow Type
String	Utf8
Boolean	Boolean
Int32	Int32
Int64	Int64
Double	Float64
Decimal128	Decimal128
Binary	Binary
Datetime without time	Date32
Datetime with time	Timestamp(Millisecond, <Timezone>)
Timestamp	Timestamp(Millisecond, None)
Array	List<Utf8>
Null	Null
Undefined	Null
RegularExpression	Utf8
JavaScriptCode	Utf8
JavaScriptCodeWithScope	Utf8
Symbol	Utf8
MaxKey	Utf8
MinKey	Utf8
DbPointer	Utf8
ObjectId	Utf8
Document	See unnesting section

note

• The MongoDB Datetime value is retrieved as a UTC time value by default. Use the mongodb_time_zone configuration parameter to specify the desired time zone for interpreting TIMESTAMP values during data retrieval.

Unnesting

Consider the following document:

{
  "a": 1,
  "b": {
    "x": 2,
    "y": {
      "z": 3
    }
  }
}

Using mongodb_unnest_depth you can control the unnesting behavior. Here are the examples:

mongodb_unnest_depth: 0

sql> select * from test_table;
+-----------+---------------------+
| a (Int32) | b (Utf8)            |
+-----------+---------------------+
| 1         | {"x":2,"y":{"z":3}} |
+---+-----------------------------+

mongodb_unnest_depth: 1

sql> select * from test_table;
+-----------+-------------+------------+
| a (Int32) | b.x (Int32) | b.y (Utf8) |
+-----------+-------------+------------+
| 1         | 2           | {"z":3}    | 
+-----------+-------------+------------+

mongodb_unnest_depth: 2

sql> select * from test_table;
+-----------+-------------+---------------+
| a (Int32) | b.x (Int32) | b.y.z (Int32) |
+-----------+-------------+---------------+
| 1         | 2           | 3             |
+-----------+-------------+---------------+

Examples

Connecting using username and password and custom auth table

datasets:
  - from: mongodb:my_dataset
    name: my_dataset
    params:
      mongodb_host: localhost
      mongodb_port: 27017
      mongodb_db: my_database
      mongodb_user: my_user
      mongodb_pass: ${secrets:mongodb_pass}
      mongodb_auth_source: admin

Connecting using SSL

datasets:
  - from: mongodb:my_dataset
    name: my_dataset
    params:
      mongodb_host: localhost
      mongodb_port: 27017
      mongodb_db: my_database
      mongodb_user: my_user
      mongodb_pass: ${secrets:mongodb_pass}
      mongodb_sslmode: preferred
      mongodb_sslrootcert: ./custom_cert.pem

Connecting using a Connection String

datasets:
  - from: mongodb:my_dataset
    name: my_dataset
    params:
      mongodb_connection_string: mongodb://${secrets:my_user}:${secrets:my_password}@localhost:27017/my_db?authSource=admin

Connecting to MongoDB Atlas (SRV)

When mongodb_host ends with .mongodb.net, mongodb_srv is automatically enabled and mongodb_port is ignored — mongodb+srv:// discovers host/port via DNS SRV records.

datasets:
  - from: mongodb:my_collection
    name: my_dataset
    params:
      mongodb_host: cluster0.abc123.mongodb.net
      mongodb_db: my_database
      mongodb_user: my_user
      mongodb_pass: ${secrets:mongodb_pass}

Set mongodb_srv: true explicitly for non-Atlas hosts that are configured with SRV records:

datasets:
  - from: mongodb:my_collection
    name: my_dataset
    params:
      mongodb_srv: true
      mongodb_host: mongo.example.com
      mongodb_db: my_database
      mongodb_user: my_user
      mongodb_pass: ${secrets:mongodb_pass}

With custom connection pool settings

datasets:
  - from: mongodb:my_dataset
    name: my_dataset
    params:
      mongodb_host: localhost
      mongodb_port: 27017
      mongodb_db: my_database
      mongodb_user: my_user
      mongodb_pass: ${secrets:mongodb_pass}
      mongodb_pool_min: 5
      mongodb_pool_max: 10

Using MongoDB Change Streams

Spice supports real-time Change Data Capture (CDC) from MongoDB using native MongoDB Change Streams. This streams inserts, updates, replacements, deletes, and collection-level invalidation events from MongoDB collections directly into Spice accelerators.

How it works

On startup, Spice opens a Change Stream on the source collection (fullDocument=updateLookup), emits a CDC TRUNCATE, applies a full snapshot of the collection as upsert rows, signals readiness, then processes Change Stream events in batches. Opening the Change Stream before the snapshot prevents gaps between the snapshot and the live stream.

File-accelerated datasets persist resume tokens and resume from the last committed token on restart. In-memory accelerators re-bootstrap from a fresh snapshot.

Prerequisites

• MongoDB 4.0+ with Change Streams enabled. MongoDB requires a replica set or sharded cluster for Change Streams.
• The MongoDB user must have changeStream privileges.
• The accelerator must support upsert behavior. Use duckdb, sqlite, postgres, turso, or cayenne.
• acceleration.primary_key: _id is required. Delete events only include the document key, so Spice needs _id to route deletes.
• acceleration.on_conflict must specify upsert on _id so update and replace events overwrite existing rows.

Minimal configuration

datasets:
  - from: mongodb:users
    name: users
    params:
      mongodb_host: localhost
      mongodb_port: '27017'
      mongodb_db: my_database
      mongodb_user: my_user
      mongodb_pass: ${secrets:mongodb_pass}
    acceleration:
      enabled: true
      engine: duckdb
      refresh_mode: changes
      primary_key: _id
      on_conflict:
        _id: upsert

Change Stream parameters

These optional runtime parameters live under dataset params:. The first four are not prefixed with mongodb_.

Parameter Name	Default	Description
change_stream_batch_max_size	1000	Maximum number of Change Stream events to group into one CDC batch before applying it. Must be greater than 0.
change_stream_batch_max_duration	1s	Maximum time to wait for a Change Stream batch to fill before applying it. Accepts fundu duration strings; must be greater than 0.
change_stream_max_await_time	1s	Maximum time MongoDB waits for new Change Stream events before returning an empty server batch. Accepts fundu duration strings; must be greater than 0.
change_stream_batch_size	1000	Number of Change Stream events MongoDB should request from the server per batch. Must fit in a u32 and be greater than 0.
mongodb_resume_token_invalid_behavior	error	Behavior when a persisted Change Stream resume token cannot be honored by the server (e.g. the token is past the oplog retention window). error surfaces a clear error so the operator can decide; rebootstrap drops the persisted token and re-snapshots the collection.

The existing mongodb_unnest_depth parameter also applies to Change Stream documents, so nested BSON is flattened the same way as normal MongoDB reads.

Event mapping

• insert: create/upsert, using fullDocument.
• update: update/upsert, using fullDocument from fullDocument=updateLookup.
• replace: update/upsert, using fullDocument.
• delete: delete, using documentKey; non-key columns are null.
• drop, rename, dropDatabase, invalidate: truncate, because collection continuity is no longer guaranteed.

If MongoDB does not include fullDocument for an update or replace event, Spice fails the stream with a clear error instead of applying a partial row.

Resumability across restarts

For file-accelerated datasets (acceleration mode: file / file_create / file_update, or engine: postgres), Spice persists the most recent Change Stream resume token in a sidecar table named spice_sys_mongodb, stored alongside the accelerator data. The token is committed only after the downstream accelerator write succeeds (at-least-once semantics).

On restart with a persisted token, Spice resumes the Change Stream from that token and skips the collection snapshot. If MongoDB rejects the token (typical codes ChangeStreamHistoryLost 286 or ChangeStreamFatalError 280, e.g. when the oplog window has rolled past the token's position), the behavior is governed by mongodb_resume_token_invalid_behavior above. Re-snapshotting a large collection is opt-in by default.

Datasets that are not file-accelerated (in-memory Arrow, etc.) do not get a sidecar row; restarts re-bootstrap from a fresh snapshot.

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Secrets

Spice integrates with multiple secret stores to help manage sensitive data securely. For detailed information on supported secret stores, refer to the secret stores documentation. Additionally, learn how to use referenced secrets in component parameters by visiting the using referenced secrets guide.

Cookbook

• A cookbook recipe to configure MongoDB as a data connector in Spice. MongoDB Data Connector