MongoDB Connector#

The mongodb connector allows the use of MongoDB collections as tables in Presto.

Note

MongoDB 2.6+ is supported, although it is highly recommend to use 3.0 or later.

Configuration#

To configure the MongoDB connector, create a catalog properties file etc/catalog/mongodb.properties with the following contents, replacing the properties as appropriate:

connector.name=mongodb
mongodb.seeds=host1,host:port

Multiple MongoDB Clusters#

You can have as many catalogs as you need, so if you have additional MongoDB clusters, simply add another properties file to etc/catalog with a different name, making sure it ends in .properties). For example, if you name the property file sales.properties, Presto will create a catalog named sales using the configured connector.

Configuration Properties#

The following configuration properties are available:

Property Name

Description

mongodb.seeds

List of all MongoDB servers

mongodb.schema-collection

A collection which contains schema information

mongodb.case-insensitive-name-matching

Match database and collection names case insensitively

mongodb.credentials

List of credentials

mongodb.min-connections-per-host

The minimum size of the connection pool per host

mongodb.connections-per-host

The maximum size of the connection pool per host

mongodb.max-wait-time

The maximum wait time

mongodb.max-connection-idle-time

The maximum idle time of a pooled connection

mongodb.connection-timeout

The socket connect timeout

mongodb.socket-timeout

The socket timeout

mongodb.socket-keep-alive

Whether keep-alive is enabled on each socket

mongodb.ssl.enabled

Use TLS/SSL for connections to mongod/mongos

mongodb.read-preference

The read preference

mongodb.write-concern

The write concern

mongodb.required-replica-set

The required replica set name

mongodb.cursor-batch-size

The number of elements to return in a batch

mongodb.seeds#

Comma-separated list of hostname[:port] all MongoDB servers in the same replica set, or a list of MongoDB servers in the same sharded cluster. If a port is not specified, port 27017 will be used.

This property is required; there is no default and at least one seed must be defined.

mongodb.schema-collection#

As MongoDB is a document database, there is no fixed schema information in the system. So a special collection in each MongoDB database should define the schema of all tables. Please refer the Table Definition section for the details.

At startup, this connector tries guessing fields’ types, but it might not be correct for your collection. In that case, you need to modify it manually. CREATE TABLE and CREATE TABLE AS SELECT will create an entry for you.

This property is optional; the default is _schema.

mongodb.credentials#

A comma separated list of username:password@database credentials.

This property is optional; no default value. The database should be the authentication database for the user (e.g. admin).

mongodb.min-connections-per-host#

The minimum number of connections per host for this MongoClient instance. Those connections are kept in a pool when idle, and the pool ensures over time that it contains at least this minimum number.

This property is optional; the default is 0.

mongodb.connections-per-host#

The maximum number of connections allowed per host for this MongoClient instance. Those connections are kept in a pool when idle. Once the pool is exhausted, any operation requiring a connection blocks waiting for an available connection.

This property is optional; the default is 100.

mongodb.max-wait-time#

The maximum wait time in milliseconds, that a thread may wait for a connection to become available. A value of 0 means that it does not wait. A negative value means to wait indefinitely for a connection to become available.

This property is optional; the default is 120000.

mongodb.max-connection-idle-time#

The maximum idle time of a pooled connection in milliseconds. A value of 0 indicates no limit to the idle time. A pooled connection that has exceeded its idle time will be closed and replaced when necessary by a new connection.

This property is optional; the default is 0.

mongodb.connection-timeout#

The connection timeout in milliseconds. A value of 0 means no timeout. It is used solely when establishing a new connection.

This property is optional; the default is 10000.

mongodb.socket-timeout#

The socket timeout in milliseconds. It is used for I/O socket read and write operations.

This property is optional; the default is 0 and means no timeout.

mongodb.socket-keep-alive#

This flag controls the socket keep alive feature that keeps a connection alive through firewalls.

This property is optional; the default is false.

mongodb.ssl.enabled#

This flag enables SSL connections to MongoDB servers.

This property is optional; the default is false.

mongodb.read-preference#

The read preference to use for queries, map-reduce, aggregation, and count. The available values are PRIMARY, PRIMARY_PREFERRED, SECONDARY, SECONDARY_PREFERRED and NEAREST.

This property is optional; the default is PRIMARY.

mongodb.write-concern#

The write concern to use. The available values are ACKNOWLEDGED, FSYNC_SAFE, FSYNCED, JOURNAL_SAFEY, JOURNALED, MAJORITY, NORMAL, REPLICA_ACKNOWLEDGED, REPLICAS_SAFE and UNACKNOWLEDGED.

This property is optional; the default is ACKNOWLEDGED.

mongodb.required-replica-set#

The required replica set name. With this option set, the MongoClient instance performs the following actions:

#. Connect in replica set mode, and discover all members of the set based on the given servers
#. Make sure that the set name reported by all members matches the required set name.
#. Refuse to service any requests, if any member of the seed list is not part of a replica set with the required name.

This property is optional; no default value.

mongodb.cursor-batch-size#

Limits the number of elements returned in one batch. A cursor typically fetches a batch of result objects and stores them locally. If batchSize is 0, Driver’s default are used. If batchSize is positive, it represents the size of each batch of objects retrieved. It can be adjusted to optimize performance and limit data transfer. If batchSize is negative, it limits the number of objects returned, that fit within the max batch size limit (usually 4MB), and the cursor is closed. For example if batchSize is -10, then the server returns a maximum of 10 documents, and as many as can fit in 4MB, then closes the cursor.

Note

Do not use a batch size of 1.

This property is optional; the default is 0.

Table Definition#

MongoDB maintains table definitions on the special collection where mongodb.schema-collection configuration value specifies.

Note

There’s no way for the plugin to detect a collection is deleted. You need to delete the entry by db.getCollection("_schema").remove( { table: deleted_table_name }) in the Mongo Shell. Or drop a collection by running DROP TABLE table_name using Presto.

A schema collection consists of a MongoDB document for a table.

{
    "table": ...,
    "fields": [
          { "name" : ...,
            "type" : "varchar|bigint|boolean|double|date|array(bigint)|...",
            "hidden" : false },
            ...
        ]
    }
}

Field

Required

Type

Description

table

required

string

Presto table name

fields

required

array

A list of field definitions. Each field definition creates a new column in the Presto table.

Each field definition:

{
    "name": ...,
    "type": ...,
    "hidden": ...
}

Field

Required

Type

Description

name

required

string

Name of the column in the Presto table.

type

required

string

Presto type of the column.

hidden

optional

boolean

Hides the column from DESCRIBE <table name> and SELECT *. Defaults to false.

There is no limit on field descriptions for either key or message.

ObjectId#

MongoDB collection has the special field _id. The connector tries to follow the same rules for this special field, so there will be hidden field _id.

CREATE TABLE IF NOT EXISTS orders (
    orderkey bigint,
    orderstatus varchar,
    totalprice double,
    orderdate date
);

INSERT INTO orders VALUES(1, 'bad', 50.0, current_date);
INSERT INTO orders VALUES(2, 'good', 100.0, current_date);
SELECT _id, * FROM orders;
                 _id                 | orderkey | orderstatus | totalprice | orderdate
-------------------------------------+----------+-------------+------------+------------
 55 b1 51 63 38 64 d6 43 8c 61 a9 ce |        1 | bad         |       50.0 | 2015-07-23
 55 b1 51 67 38 64 d6 43 8c 61 a9 cf |        2 | good        |      100.0 | 2015-07-23
(2 rows)
SELECT _id, * FROM orders WHERE _id = ObjectId('55b151633864d6438c61a9ce');
                 _id                 | orderkey | orderstatus | totalprice | orderdate
-------------------------------------+----------+-------------+------------+------------
 55 b1 51 63 38 64 d6 43 8c 61 a9 ce |        1 | bad         |       50.0 | 2015-07-23
(1 row)

You can render the _id field to readable values with a cast to VARCHAR:

SELECT CAST(_id AS VARCHAR), * FROM orders WHERE _id = ObjectId('55b151633864d6438c61a9ce');
           _id             | orderkey | orderstatus | totalprice | orderdate
---------------------------+----------+-------------+------------+------------
 55b151633864d6438c61a9ce  |        1 | bad         |       50.0 | 2015-07-23
(1 row)

Limitations#

The following operations are not supported: