How to Migrate from ClickHouse to ParadeDB in PostgreSQL

How do I migrate data from ClickHouse to ParadeDB without downtime?

Move data, schema, and queries from ClickHouse to ParadeDB with minimal downtime.

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Description

What does “migrating from ClickHouse to ParadeDB” mean?

You copy tables, re-create schemas, and load data so that existing ClickHouse workloads can run on ParadeDB (a Postgres-based OLAP engine) without code rewrites.

Which high-level steps are required?

1) Export data from ClickHouse.
2) Convert schema to ParadeDB-compatible SQL.
3) Create tables in ParadeDB.
4) Import data.
5) Validate counts and queries.
6) Cut over traffic.

How do I export ClickHouse tables quickly?

Use clickhouse-client with CSV format because ParadeDB’s COPY command ingests CSV efficiently:

clickhouse-client \ --query="SELECT * FROM ecommerce.Customers FORMAT CSV" \ --compress 1 \ > Customers.csv.gz

Repeat for Orders, Products, and OrderItems.

How do I map ClickHouse data types to ParadeDB?

Match every column:
• UInt64 → BIGINT
• DateTime64 → TIMESTAMP
• Decimal(10,2) → NUMERIC(10,2)
• LowCardinality(String) → TEXT WITH (paradedb.low_cardinality=true)

How do I create tables in ParadeDB?

Connect with psql and run the converted DDL:

CREATE TABLE Customers( id BIGINT PRIMARY KEY, name TEXT, email TEXT, created_at TIMESTAMP ); -- Repeat for Orders, Products, OrderItems

What’s the fastest way to load the exported CSV?

ENABLE parallel COPY, then stream files:

\copy Customers FROM PROGRAM 'gunzip -c Customers.csv.gz' WITH (FORMAT csv)

Load the largest tables first to overlap network and disk usage.

How do I confirm data integrity?

Compare row counts and aggregates:

SELECT count(*) FROM Customers; -- Expected: same as ClickHouse SELECT SUM(total_amount) FROM Orders;

Can I migrate without downtime?

Yes.Perform an initial full load, then use incremental replication (e.g., Kafka or materialized views) to sync writes. Schedule a final short lock window to switch applications.

Best practices for production migrations

• Test on staging with production-sized data.
• Use NUMERIC for money fields.
• Keep ClickHouse running until ParadeDB proves stable.
• Monitor disk and autovacuum after large COPY.

What are the key ParadeDB features you gain?

You keep PostgreSQL ACID guarantees, get advanced indexing, vector search, and still enjoy columnar performance through ParadeDB extensions.

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

How to Migrate from ClickHouse to ParadeDB in PostgreSQL Example Usage


-- Validate after migration
SELECT c.name, COUNT(o.id) AS orders
FROM Customers c
JOIN Orders o ON o.customer_id = c.id
GROUP BY c.name
ORDER BY orders DESC
LIMIT 10;

How to Migrate from ClickHouse to ParadeDB in PostgreSQL Syntax


# 1. Export from ClickHouse
a) Full table to compressed CSV
clickhouse-client --query="SELECT * FROM ecommerce.Customers FORMAT CSV" \
  --compress 1 > Customers.csv.gz

# 2. Generate ParadeDB DDL (simplified example)
CREATE TABLE Customers(
  id BIGINT PRIMARY KEY,
  name TEXT,
  email TEXT,
  created_at TIMESTAMP
);

# 3. Import into ParadeDB (psql shell)
\copy Customers FROM PROGRAM 'gunzip -c Customers.csv.gz' WITH (FORMAT csv)

OPTIONS & FLAGS
--compress <0|1>        gzip output on the fly
FORMAT CSV              ensures COPY compatibility
WITH (FORMAT csv)       tells Postgres to parse CSV
PROGRAM                 streams data without temp files

Common Mistakes

Ignoring data-type mismatches. ClickHouse UInt8 to ParadeDB SMALLINT may overflow; choose BIGINT or explicit casting before COPY.
Loading data with default work_mem. Large COPY operations need increased maintenance_work_mem to avoid slow imports; adjust in postgresql.conf or SET locally.