MySQL to ClickHouse

Target DataSource：

ClickHouse

Connection

Basic Functions

Function	Description
Schema Migration	If the target schema does not exist, BladePipe will automatically generate and execute CREATE statements based on the source metadata and the mapping rule.
Full Data Migration	Migrate data by sequentially scanning data in tables and writing it in batches to the target database.
Incremental Data Sync	Sync of common DML like INSERT, UPDATE, DELETE is supported.
Data Verification	Verify all existing data. Scheduled DataTasks are supported.
Subscription Modification	Add, delete, or modify the subscribed tables with support for historical data migration. For more information, see Modify Subscription.
Position Resetting	Reset positions by file position or timestamp. Allow re-consumption of incremental data logs in a past period or since a specific Binlog file and position.
Table Name Mapping	Support the mapping rules, namely, keeping the name the same as that in Source, converting the text to lowercase, converting the text to uppercase, truncating the name by "_digit" suffix.
DDL Sync	ALTER TABLE ADD COLUMN, DROP COLUMN, MODIFY COLUMN, CHANGE COLUMN CREATE TABLE (whole database sync)
Metadata Retrieval	Retrieve the target metadata with filtering conditions or target primary keys set from the source table.

Advanced Functions

Function	Description
Write in Append Mode	INSERT and UPDATE statements are written in batches in append mode, and DELETE statements are executed individually through ALTER statements.
Scheduled Table Optimization	By setting the parameter autoOptimizeThresholdSec, the tables are optimized regularly.
Scheduled Full Data Migration	For more information, see Create Scheduled Full Data DataJob.
Custom Code	For more information, see Custom Code Processing, Debug Custom Code and Logging in Custom Code.
Data Filtering Conditions	Support data filtering using WHERE conditions, with SQL-92 as the SQL language. For more information, see Data Filtering.
Setting Target Primary Key	Change the primary key to another field to facilitate data aggregation and other operations.
Adding Virtual Columns	Support adding custom virtual columns with fixed values, such as region, ID, etc.

Limits

Limit	Description
MySQL Storage Engine	Support InnoDB, MyISAM, AWS XEngine. Other storage engines have not been tested yet.
MySQL Character Set	Support utf8, utf8mb4, latin1. Other encodings have not been tested yet.
Special Operation	Too many DELETE operations (>50 records/second) significantly affect data synchronization performance.
Target Table Engine	Only the following table engines and corresponding source table types are supported: MergeTree(tables without primary keys) ReplacingMergeTree(tables with primary keys) ReplicatedMergeTree(tables without primary keys) ReplicatedReplacingMergeTree(tables with primary keys)

FAQ

• How to handle MySQL DataJob latency?

• What to do when binary Log cannot be found in MySQL Source?

• What to do when access to schema in MySQL Source is denied?

  Tip: MySQL source-related FAQ also applies to MySQL-based DataSources.

---

Source

Prerequisites

Prerequisite	Description
Permissions for Account	See Permissions Required for MySQL/MariaDB.
Enabling Binlog	[mysqld] log-bin=mysql-bin # Enable Binlog binlog-format=ROW # Choose ROW mode binlog_row_image=FULL # Changes include all column data

Parameters

Parameter	Description
parseBinlogParallel	Number of threads for parallel parsing of Binlog in Incremental DataJobs.
parseBinlogBufferSize	Size of the circular buffer for parsing Binlog in Incremental DataJobs.
maxTransactionSize	Maximum number of data rows per transaction. If exceeded, the transaction will be split and flushed in parts.
limitThroughputMb	Limit the throughput of incremental Binlogs.
extraDDL	Support synchronization of additional DDL, including PT, GHOST, ALI_DMS, and PT_GHOST.
needJsonEscape	Escape special characters in JSON to be written to the target database.
fullDataSqlConditionEnabled	Add filtering conditions in SQL during source data scanning. It only works in Full Data migration.
srcTimeZone	Source time zone, e.g., +08:00, Asia/Shanghai, America/New_York, etc.

Tips: To modify the general parameters, see General Parameters and Functions.

---

Target

Prerequisites

Prerequisite	Description
Permissions for Account	SELECT, INSERT and common DDL permissions.
Port Preparation	Allow the migration and sync node (Worker) to connect to the ClickHouse port (e.g., 8123).

Parameters

Parameter	Description
multiReplica	Whether there are multiple replicas in a cluster.
clusterName	Cluster name. When multiReplica is true, the ON CLUSTER clusterName clause is automatically added to DDL/DML.
ckTableEngine	The following table engines are currently supported: MergeTree ReplacingMergeTree ReplicatedMergeTree ReplicatedReplacingMergeTree
autoOptimizeThresholdSec	Interval of scheduled table optimization (optimize table final). If the value <=0, it means the feature is disabled.
enableTimeRangeClamping	Whether to enable time range clamping. Forces date and time values to be constrained within the valid ClickHouse JDBC range. Values outside this range will be clamped to the minimum or maximum values. Disabled by default (false). Ranges after clamping(UTC)： Date：[1970-01-01, 2149-06-06] Date32：[1925-01-01, 2283-11-11] Timestamp：[1970-01-01 00:00:00, 2106-02-07 14:28:15] Timestamp64：[1925-01-01 08:00:00.000, 2283-11-12 07:59:59.000]

Tips: To modify the general parameters, see General Parameters and Functions.