NOT_IMPLEMENTED ClickHouse error¶

The NOT_IMPLEMENTED error in ClickHouse (and Tinybird) happens when you try to use a feature, function, or operation that isn't implemented in ClickHouse or isn't available in your version. This commonly occurs when using features from other database systems or trying to use newer ClickHouse features in older versions.

What causes this error¶

You'll typically see it when:

• Using features from other database systems (MySQL, PostgreSQL, etc.)
• Using newer ClickHouse features in older versions
• Using unsupported SQL operations
• Using client-specific features that aren't implemented
• Using deprecated or removed functionality

Example errors¶

SELECT * FROM events FOR UPDATE

SELECT * FROM events OFFSET 10 ROWS FETCH NEXT 5 ROWS ONLY

UPDATE events SET event_type = 'click' WHERE user_id = 123

SELECT * FROM events USING SAMPLE 0.1

How to fix it¶

Use ClickHouse-compatible syntax¶

Replace unsupported features with ClickHouse equivalents:

SELECT * FROM events LIMIT 5 OFFSET 10

Use supported operations¶

Replace unsupported operations with supported alternatives:

INSERT INTO events_new SELECT * FROM events WHERE user_id != 123
INSERT INTO events_new (user_id, event_type) VALUES (123, 'click')

Check ClickHouse version¶

Verify feature support in your ClickHouse version:

SELECT version()

Use alternative approaches¶

Find alternative ways to achieve the same result:

SELECT * FROM events SAMPLE 0.1

Common patterns and solutions¶

Pagination¶

ClickHouse pagination syntax:

SELECT * FROM events ORDER BY timestamp DESC LIMIT 10 OFFSET 20

Data modification¶

ClickHouse doesn't support UPDATE/DELETE like other databases:

-- Use INSERT with deduplication
INSERT INTO events_new SELECT * FROM events WHERE user_id != 123
INSERT INTO events_new (user_id, event_type) VALUES (123, 'click')

Using MergeTree engines for "updates"¶

CREATE TABLE events_replacing (
    user_id UInt32,
    event_type String,
    timestamp DateTime
) ENGINE = ReplacingMergeTree() ORDER BY user_id

-- Insert new row to "update"
INSERT INTO events_replacing VALUES (123, 'click', now())

Sampling¶

ClickHouse sampling syntax:

SELECT * FROM events SAMPLE 0.1
SELECT * FROM events SAMPLE 1000 ROWS

Transactions¶

ClickHouse has limited transaction support:

-- Use atomic operations where possible
-- Consider using Materialized Views for complex updates

Advanced solutions¶

Using Materialized Views¶

For complex data modifications:

CREATE MATERIALIZED VIEW events_updated AS
SELECT
    user_id,
    CASE WHEN user_id = 123 THEN 'click' ELSE event_type END as event_type,
    timestamp
FROM events

Using INSERT with deduplication¶

For data replacement:

INSERT INTO events_new
SELECT
    user_id,
    CASE WHEN user_id = 123 THEN 'click' ELSE event_type END as event_type,
    timestamp
FROM events

Using window functions¶

For complex aggregations:

SELECT
    user_id,
    event_type,
    ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY timestamp) as row_num
FROM events

ClickHouse-specific features¶

Using ReplacingMergeTree¶

For handling updates:

CREATE TABLE events_replacing (
    user_id UInt32,
    event_type String,
    timestamp DateTime,
    version UInt32
) ENGINE = ReplacingMergeTree(version)
ORDER BY (user_id, timestamp)

Using CollapsingMergeTree¶

For handling deletes:

CREATE TABLE events_collapsing (
    user_id UInt32,
    event_type String,
    timestamp DateTime,
    sign Int8
) ENGINE = CollapsingMergeTree(sign)
ORDER BY (user_id, timestamp)

Feature compatibility¶

MySQL to ClickHouse¶

PostgreSQL to ClickHouse¶

Tinybird-specific notes¶

In Tinybird, this error often occurs when:

• Using unsupported ClickHouse features in Pipes
• Trying to use features not available in Tinybird's ClickHouse version
• Using client-specific methods that aren't supported
• Working with Materialized Views that use unsupported operations

To debug in Tinybird:

1. Check Tinybird's ClickHouse version and supported features
2. Use the Query Builder to test operations
3. Consult Tinybird documentation for supported features
4. Use alternative approaches for unsupported operations

Best practices¶

Feature compatibility¶

• Check ClickHouse documentation before using new features
• Test operations in development environment first
• Use version-specific feature checks
• Keep up with ClickHouse updates and changes

Alternative approaches¶

• Use Materialized Views for complex data modifications
• Implement logic in application layer when needed
• Use INSERT with deduplication for updates
• Consider using specialized table engines

Error handling¶

• Implement proper error handling for unsupported features
• Have fallback approaches ready
• Log unsupported feature attempts
• Document workarounds for common issues

See also¶

• ClickHouse Table Engines
• Working with Data Sources
• Common function errors