How to Migrate from Clickhouse to Snowflake

How do I migrate data and schema from ClickHouse to Snowflake?

Move data, schema, and workloads from ClickHouse to Snowflake with minimal downtime.

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Description

Why migrate from ClickHouse to Snowflake?

Teams switch to Snowflake for elastic scaling, zero-copy cloning, and a robust ecosystem. Migration reduces admin overhead and unlocks native features like Snowpark and Snowpipe.

What are the high-level migration steps?

1) Export ClickHouse tables to external storage (Parquet/CSV)
2) Create equivalent schemas in Snowflake
3) Load historical data with COPY INTO
4) Validate row counts & aggregates
5) Incrementally sync new records with Snowpipe or Kafka Connector
6) Cut over applications

How do I export ClickHouse data efficiently?

Use clickhouse-client with \G format Parquet for compressed columnar files:
$ clickhouse-client --query "SELECT * FROM Orders" --format Parquet > orders.parquet

Tip:

Partition large tables by date to parallelize exports and avoid lengthy locks.

How do I create matching tables in Snowflake?

Generate DDL via ClickHouse DESCRIBE or system.columns, then map types:
• String → VARCHAR
• DateTime → TIMESTAMP_NTZ
• Decimal → NUMBER(38, scale)
• UInt64 → NUMBER(38)
Remember clustering keys become CLUSTER BY in Snowflake.

What is the COPY INTO syntax?

Snowflake COPY INTO ingests staged files in parallel, supports on-error actions, and can load Parquet natively.

How do I perform incremental loads?

Option 1: Kafka → Snowflake Connector streams inserts.
Option 2: Periodic ClickHouse export of delta partitions, then COPY INTO with PATTERN='.*2024-06.*'.

How can I verify data integrity?

Run row counts, MIN/MAX timestamps, and checksum queries in both systems. Example:
SELECT COUNT(*) AS c, SUM(total_amount) AS s FROM Orders;

When should I cut over?

After incremental lag is <1 minute and all queries pass in Snowflake. Switch application connection strings and freeze ClickHouse writes.

Why How to Migrate from Clickhouse to Snowflake is important

How to Migrate from Clickhouse to Snowflake Example Usage


-- Backfill last 7 days of OrderItems
COPY INTO OrderItems
  FROM @my_stage/order_items/
  PATTERN = '.*2024-06-[0-9]{2}.*.parquet'
  FILE_FORMAT = (TYPE = PARQUET)
  ON_ERROR = 'ABORT_STATEMENT';

How to Migrate from Clickhouse to Snowflake Syntax


-- 1. Create target table
CREATE OR REPLACE TABLE Orders (
  id           NUMBER(38)            ,
  customer_id  NUMBER(38)            ,
  order_date   TIMESTAMP_NTZ         ,
  total_amount NUMBER(10,2)
) CLUSTER BY (order_date);

-- 2. Stage files in S3 bucket integrated as @my_stage
PUT file://exports/orders/*.parquet @my_stage/orders auto_compress=true;

-- 3. Bulk load
COPY INTO Orders
  FROM @my_stage/orders
  FILE_FORMAT = (TYPE = PARQUET)
  ON_ERROR   = 'CONTINUE';

-- 4. Verify
SELECT COUNT(*)       AS rows_loaded,
       SUM(total_amount) AS sales_total
FROM   Orders;

Common Mistakes

Skipping data-type mapping leads to numeric overflows. Always translate UInt64 to NUMBER(38) and DateTime to TIMESTAMP_NTZ before loading.
Loading huge CSVs without compression slows ingest. Export Parquet or gzip CSVs and enable auto_compress for faster COPY.