How to Ensure GDPR Compliance in ClickHouse

Galaxy Glossary

How do I make ClickHouse GDPR compliant?

Use TTLs, partition-level deletes, and role-based security to fulfill GDPR obligations in ClickHouse.

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Description

Example H2

Example H3

What GDPR tasks must I handle in ClickHouse?

Delete personal data on request, retain only necessary data, and protect data from unauthorized access. ClickHouse offers TTL clauses, ALTER TABLE … DELETE, and granular privileges to achieve this.

How do I remove a customer on request?

Issue an ALTER TABLE … DELETE WHERE to wipe all rows containing that customer’s ID or email. Run a OPTIMIZE TABLE … FINAL afterwards to purge data files.

ALTER TABLE Orders DELETE WHERE customer_id = 42; OPTIMIZE TABLE Orders FINAL;

Can I schedule automatic data expiry?

Add a TTL clause during table creation or via ALTER TABLE … MODIFY TTL. TTL moves expired rows to another table or deletes them, ensuring retention limits.

ALTER TABLE Customers MODIFY TTL created_at + INTERVAL 3 YEAR DELETE;

How do I prevent unauthorized reads?

Create roles with least-privilege grants and attach them to users. Mask sensitive columns with views or omit them entirely in restricted roles.

CREATE ROLE analyst; GRANT SELECT(name, created_at) ON Customers TO analyst; GRANT analyst TO bob;

When should I use column-level encryption?

Encrypt PII such as emails before insert. ClickHouse has no built-in transparent encryption, so encrypt in the application layer and store ciphertext.

Best practice: keep a deletion log

Write each GDPR deletion into a dedicated gdpr_events table. This audit trail proves compliance during regulatory reviews.

Why How to Ensure GDPR Compliance in ClickHouse is important

How to Ensure GDPR Compliance in ClickHouse Example Usage


-- Remove all traces of a customer that requested erasure (id = 42)
ALTER TABLE Customers DELETE WHERE id = 42;
ALTER TABLE Orders DELETE WHERE customer_id = 42;
ALTER TABLE OrderItems DELETE WHERE order_id IN (
  SELECT id FROM Orders WHERE customer_id = 42
);
-- Compact data files so they disappear from disk
OPTIMIZE TABLE Customers FINAL;

How to Ensure GDPR Compliance in ClickHouse Syntax


-- Delete customer data immediately
ALTER TABLE Customers DELETE WHERE id = 42;
ALTER TABLE Orders DELETE WHERE customer_id = 42;
ALTER TABLE OrderItems DELETE WHERE order_id IN (
    SELECT id FROM Orders WHERE customer_id = 42
);
OPTIMIZE TABLE Customers FINAL;
OPTIMIZE TABLE Orders FINAL;
OPTIMIZE TABLE OrderItems FINAL;

-- Add a 3-year retention policy to Orders
ALTER TABLE Orders
MODIFY TTL order_date + INTERVAL 3 YEAR DELETE;

-- Grant analysts access to non-PII columns only
CREATE ROLE analyst;
GRANT SELECT(id, order_date, total_amount) ON Orders TO analyst;
GRANT analyst TO bob;

Common Mistakes

Ignoring the need to run OPTIMIZE after DELETE: Without <code>OPTIMIZE … FINAL</code>, deleted blocks linger on disk. Always optimize to physically purge data.
Using broad SELECT grants: Granting <code>SELECT</code> on * exposes PII to all users. Create roles and limit column access to enforce data-minimization.