2.9 KiB
slug | sidebar_position | sidebar_label |
---|---|---|
/en/engines/table-engines/integrations/mongodb | 135 | MongoDB |
MongoDB
MongoDB engine is read-only table engine which allows to read data from remote MongoDB collection.
Only MongoDB v3.6+ servers are supported.
Types mappings
MongoDB | ClickHouse |
---|---|
bool | UInt8 |
int32 | Int32 |
int64 | Int64 |
double | Float64 |
date | Date, DateTime, DateTime64 |
timestamp | Date, DateTime, DateTime64 |
string | String, UUID |
document | String(as JSON) |
array | String(as JSON) |
oid | String |
If key not found in MongoDB document, default value or null(if the column is nullable) will be inserted.
Supported conditions
WHERE
Only constant literals are allowed.
Types that can be used in WHERE section:
- Null
- UInt64
- Int64
- Float64
- String
- Array
- Tuple
- Map
- UUID
- Bool
- Object
Prewhere is not supported.
LIMIT and OFFSET
Only LIMIT
is supported.
ORDER BY
Simple expressions only are supported, without any modification like COLLATE, WITH, TO, etc.
WINDOW
Not supported.
GROUP BY
Not supported.
Aggregation functions
Not supported.
Creating a Table
CREATE TABLE [IF NOT EXISTS] [db.]table_name
(
name1 [type1],
name2 [type2],
...
) ENGINE = MongoDB(host:port, database, collection, user, password [, options]);
Engine Parameters
-
host:port
— MongoDB server address. -
database
— Remote database name. -
collection
— Remote collection name. -
user
— MongoDB user. -
password
— User password. -
options
— MongoDB connection string options (optional parameter).
:::tip If you are using the MongoDB Atlas cloud offering please add these options:
'connectTimeoutMS=10000&ssl=true&authSource=admin'
:::
Usage Example
Create a table in ClickHouse which allows to read data from MongoDB collection:
CREATE TABLE mongo_table
(
key UInt64,
data String
) ENGINE = MongoDB('mongo1:27017', 'test', 'simple_table', 'testuser', 'clickhouse');
To read from an SSL secured MongoDB server:
CREATE TABLE mongo_table_ssl
(
key UInt64,
data String
) ENGINE = MongoDB('mongo2:27017', 'test', 'simple_table', 'testuser', 'clickhouse', 'ssl=true');
Query:
SELECT COUNT() FROM mongo_table;
┌─count()─┐
│ 4 │
└─────────┘
You can also adjust connection timeout:
CREATE TABLE mongo_table
(
key UInt64,
data String
) ENGINE = MongoDB('mongo2:27017', 'test', 'simple_table', 'testuser', 'clickhouse', 'connectTimeoutMS=100000');
Troubleshooting
You can see the generated MongoDB query in DEBUG level logs.