Clickhouse

Clickhouse sink connector

Support Those Engines

Spark
Flink
SeaTunnel Zeta

Key Features

• exactly-once
• cdc

The Clickhouse sink plug-in can achieve accuracy once by implementing idempotent writing, and needs to cooperate with aggregatingmergetree and other engines that support deduplication.

Description

Used to write data to Clickhouse.

Supported DataSource Info

In order to use the Clickhouse connector, the following dependencies are required. They can be downloaded via install-plugin.sh or from the Maven central repository.

Datasource	Supported Versions	Dependency
Clickhouse	universal	Download

Data Type Mapping

SeaTunnel Data Type	Clickhouse Data Type
STRING	String / Int128 / UInt128 / Int256 / UInt256 / Point / Ring / Polygon MultiPolygon
INT	Int8 / UInt8 / Int16 / UInt16 / Int32
BIGINT	UInt64 / Int64 / IntervalYear / IntervalQuarter / IntervalMonth / IntervalWeek / IntervalDay / IntervalHour / IntervalMinute / IntervalSecond
DOUBLE	Float64
DECIMAL	Decimal
FLOAT	Float32
DATE	Date
TIME	DateTime
ARRAY	Array
MAP	Map

Sink Options

Name	Type	Required	Default	Description
host	String	Yes	-	ClickHouse cluster address, the format is host:port , allowing multiple hosts to be specified. Such as "host1:8123,host2:8123".
database	String	Yes	-	The ClickHouse database.
table	String	Yes	-	The table name.
username	String	Yes	-	ClickHouse user username.
password	String	Yes	-	ClickHouse user password.
clickhouse.config	Map	No		In addition to the above mandatory parameters that must be specified by clickhouse-jdbc , users can also specify multiple optional parameters, which cover all the parameters provided by clickhouse-jdbc.
bulk_size	String	No	20000	The number of rows written through Clickhouse-jdbc each time, the default is 20000.
split_mode	String	No	false	This mode only support clickhouse table which engine is 'Distributed'.And internal_replication option-should be true.They will split distributed table data in seatunnel and perform write directly on each shard. The shard weight define is clickhouse will counted.
sharding_key	String	No	-	When use split_mode, which node to send data to is a problem, the default is random selection, but the 'sharding_key' parameter can be used to specify the field for the sharding algorithm. This option only worked when 'split_mode' is true.
primary_key	String	No	-	Mark the primary key column from clickhouse table, and based on primary key execute INSERT/UPDATE/DELETE to clickhouse table.
support_upsert	Boolean	No	false	Support upsert row by query primary key.
allow_experimental_lightweight_delete	Boolean	No	false	Allow experimental lightweight delete based on *MergeTree table engine.
schema_save_mode	Enum	no	CREATE_SCHEMA_WHEN_NOT_EXIST	Schema save mode. Please refer to the schema_save_mode section below.
data_save_mode	Enum	no	APPEND_DATA	Data save mode. Please refer to the data_save_mode section below.
save_mode_create_template	string	no	see below	See below.
common-options		No	-	Sink plugin common parameters, please refer to Sink Common Options for details.

schema_save_mode[Enum]

Before starting the synchronization task, choose different processing options for the existing table schema.
Option descriptions:
RECREATE_SCHEMA: Create the table if it does not exist; drop and recreate the table when saving.
CREATE_SCHEMA_WHEN_NOT_EXIST: Create the table if it does not exist; skip if the table already exists.
ERROR_WHEN_SCHEMA_NOT_EXIST: Throw an error if the table does not exist.
IGNORE: Ignore the processing of the table.

data_save_mode[Enum]

Before starting the synchronization task, choose different processing options for the existing data on the target side.
Option descriptions:
DROP_DATA: Retain the database schema but delete the data.
APPEND_DATA: Retain the database schema and the data.
CUSTOM_PROCESSING: Custom user-defined processing.
ERROR_WHEN_DATA_EXISTS: Throw an error if data exists.

save_mode_create_template

Automatically create Doris tables using templates.
The table creation statements will be generated based on the upstream data types and schema. The default template can be modified as needed.

Default template:

CREATE TABLE IF NOT EXISTS `${database}`.`${table}` (
    ${rowtype_primary_key},
    ${rowtype_fields}
) ENGINE = MergeTree()
ORDER BY (${rowtype_primary_key})
PRIMARY KEY (${rowtype_primary_key})
SETTINGS
    index_granularity = 8192;

If custom fields are added to the template, for example, adding an id field:

CREATE TABLE IF NOT EXISTS `${database}`.`${table}` (
    id,
    ${rowtype_fields}
) ENGINE = MergeTree()
    ORDER BY (${rowtype_primary_key})
    PRIMARY KEY (${rowtype_primary_key})
    SETTINGS
    index_granularity = 8192;

The connector will automatically retrieve the corresponding types from the upstream source and fill in the template, removing the id field from the rowtype_fields. This method can be used to modify custom field types and attributes.

The following placeholders can be used:

• database: Retrieves the database from the upstream schema.
• table_name: Retrieves the table name from the upstream schema.
• rowtype_fields: Retrieves all fields from the upstream schema and automatically maps them to Doris field descriptions.
• rowtype_primary_key: Retrieves the primary key from the upstream schema (this may be a list).
• rowtype_unique_key: Retrieves the unique key from the upstream schema (this may be a list).

How to Create a Clickhouse Data Synchronization Jobs

The following example demonstrates how to create a data synchronization job that writes randomly generated data to a Clickhouse database:

# Set the basic configuration of the task to be performed
env {
  parallelism = 1
  job.mode = "BATCH"
  checkpoint.interval  = 1000
}

source {
  FakeSource {
      row.num = 2
      bigint.min = 0
      bigint.max = 10000000
      split.num = 1
      split.read-interval = 300
      schema {
        fields {
          c_bigint = bigint
        }
      }
    }
}

sink {
  Clickhouse {
    host = "127.0.0.1:9092"
    database = "default"
    table = "test"
    username = "xxxxx"
    password = "xxxxx"
  }
}

Tips

1.SeaTunnel Deployment Document.
2.The table to be written to needs to be created in advance before synchronization.
3.When sink is writing to the ClickHouse table, you don't need to set its schema because the connector will query ClickHouse for the current table's schema information before writing.

Clickhouse Sink Config

sink {
  Clickhouse {
    host = "localhost:8123"
    database = "default"
    table = "fake_all"
    username = "xxxxx"
    password = "xxxxx"
    clickhouse.config = {
      max_rows_to_read = "100"
      read_overflow_mode = "throw"
    }
  }
}

Split Mode

sink {
  Clickhouse {
    host = "localhost:8123"
    database = "default"
    table = "fake_all"
    username = "xxxxx"
    password = "xxxxx"
    
    # split mode options
    split_mode = true
    sharding_key = "age"
  }
}

CDC(Change data capture) Sink

sink {
  Clickhouse {
    host = "localhost:8123"
    database = "default"
    table = "fake_all"
    username = "xxxxx"
    password = "xxxxx"
    
    # cdc options
    primary_key = "id"
    support_upsert = true
  }
}

CDC(Change data capture) for *MergeTree engine

sink {
  Clickhouse {
    host = "localhost:8123"
    database = "default"
    table = "fake_all"
    username = "xxxxx"
    password = "xxxxx"
    
    # cdc options
    primary_key = "id"
    support_upsert = true
    allow_experimental_lightweight_delete = true
  }
}