5.11. MongoDB Connector

This 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 fileetc/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 additionalMongoDB clusters, simply add another properties file to etc/catalogwith a different name (making sure it ends in .properties). Forexample, if you name the property file sales.properties, Prestowill create a catalog named sales using the configured connector.

Configuration Properties

The following configuration properties are available:

mongodb.seeds

Comma-separated list of hostname[:port] all mongod servers in the same replica set or a list of mongos servers in the same sharded cluster. If 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 the MongoDB is a document database, there’s no fixed schema information in the system. So a special collection in each MongoDB database should defines 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@collection credentials

This property is optional; no default value.

mongodb.min-connections-per-host

The minimum number of connections per host for this MongoClient instance. Those connections will be kept in a pool when idle, and the pool will ensure 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 will be kept in a pool when idle. Once the pool is exhausted, any operation requiring a connection will block 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 will not wait. A negative value means to wait indefinitely for a connection to become available.

This property is optional; the default is 120000.

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 areACKNOWLEDGED, 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 will

• 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 will be 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 will limit of number objects returned, that fit within the max batch size limit (usually 4MB), and cursor will be closed. For example if batchSize is -10, then the server will return a maximum of 10 documents and as many as can fit in 4MB, then close 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 },
            ...
        ]
    }
}

Each field definition:

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

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)

Note

Unfortunately, there is no way to represent _id fields more fancy like 55b151633864d6438c61a9ce.

原文: https://prestodb.io/docs/current/connector/mongodb.html