How to Migrate from MySQL to ClickHouse in PostgreSQL

How do I migrate large MySQL tables to ClickHouse without downtime?

Move data from a row-oriented MySQL database into a column-oriented ClickHouse cluster using built-in MySQL table engine and INSERT-SELECT.

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Description

Why migrate from MySQL to ClickHouse?

ClickHouse’s columnar storage delivers sub-second aggregation over billions of rows, making it ideal for ecommerce event logs, order analytics, and real-time dashboards that strain MySQL.

What prerequisites should I set up?

Provision a ClickHouse server reachable from the MySQL host, open ports 9000 (TCP) and 8123 (HTTP), and create a ClickHouse user with INSERT rights.Enable binary logging on MySQL for consistent reads.

How do I mirror MySQL tables in ClickHouse?

Generate CREATE TABLE statements with compatible data types (e.g., MySQL VARCHAR → ClickHouse String, DATETIME → DateTime). Partition large tables by day or month for fast pruning.

Which migration methods are supported?

Using the MySQL engine

Create a temporary ClickHouse table that points to MySQL.Then run INSERT INTO target SELECT * FROM mysql_engine_table to copy data in parallel.

Using clickhouse-client + CSV dumps

Dump MySQL tables into CSV or TSV with --tab, then pipe the file into clickhouse-client --query="INSERT INTO target FORMAT CSV" for bulk loading.

How to migrate with one command?

Use INSERT SELECT with the MySQL engine for an online, pull-based copy that keeps MySQL online.

How do I validate the migration?

Run COUNT(*) and SUM(total_amount) on both systems.Compare checksums or row counts to detect drift before switching production queries to ClickHouse.

What performance tuning should I apply?

Increase max_insert_threads, set max_memory_usage to available RAM, and insert in 1–5 million-row batches. Create ORDER BY clauses on high-cardinality keys like (customer_id, order_date).

How can Galaxy speed up this workflow?

Galaxy’s AI copilot autogenerates ClickHouse DDL, rewrites MySQL queries, and lets teams endorse migration scripts so every engineer runs the same, trusted SQL.

Why How to Migrate from MySQL to ClickHouse in PostgreSQL is important

How to Migrate from MySQL to ClickHouse in PostgreSQL Example Usage


-- Migrate customers and their first order date
CREATE TABLE mysql_customers ENGINE = MySQL('mysql-host:3306','ecommerce','Customers','u','p');

CREATE TABLE Customers AS mysql_customers ENGINE = MergeTree ORDER BY id;

INSERT INTO Customers SELECT * FROM mysql_customers;

-- Verify
SELECT COUNT(*) AS mysql_cnt FROM mysql_customers;
SELECT COUNT(*) AS ch_cnt FROM Customers;

How to Migrate from MySQL to ClickHouse in PostgreSQL Syntax


-- 1. Link to the MySQL source table
CREATE TABLE mysql_orders
ENGINE = MySQL('mysql-host:3306', 'ecommerce', 'Orders', 'mysql_user', 'mysql_pass');

-- 2. Create the destination ClickHouse table
CREATE TABLE Orders
(
    id UInt32,
    customer_id UInt32,
    order_date DateTime,
    total_amount Decimal(10,2)
)
ENGINE = MergeTree
PARTITION BY toYYYYMM(order_date)
ORDER BY (customer_id, order_date);

-- 3. Copy the data
INSERT INTO Orders SELECT * FROM mysql_orders;

Common Mistakes

Dumping to CSV without disabling MySQL triggers causes side-effects. Fix by exporting with --skip-triggers or using ClickHouse’s MySQL engine for a trigger-free read.
Mapping MySQL DECIMAL to ClickHouse Float64 loses precision. Use Decimal or Decimal32/64 in ClickHouse to preserve monetary values.