TOO_MANY_ROWS_OR_BYTES ClickHouse error¶

The TOO_MANY_ROWS_OR_BYTES error in ClickHouse (and Tinybird) happens when a query tries to return more rows or bytes than the configured limits allow. This is a safety mechanism to prevent queries from consuming excessive resources.

What causes this error¶

You'll typically see it when:

• Query returns too many rows (exceeds max_result_rows limit)
• Query returns too much data (exceeds max_result_bytes limit)
• Missing LIMIT clause on large datasets
• Aggregations without proper grouping produce too many results
• Window functions generate excessive intermediate results

Example errors¶

SELECT * FROM events

SELECT user_id, event_type FROM events GROUP BY user_id, event_type

SELECT *, ROW_NUMBER() OVER (ORDER BY timestamp) FROM events

SELECT * FROM users CROSS JOIN events

How to fix it¶

Add LIMIT clause¶

The most common fix is to limit the number of rows returned:

SELECT * FROM events LIMIT 1000

Use more specific WHERE clauses¶

Filter data before processing to reduce result size:

SELECT user_id, event_type
FROM events
WHERE timestamp >= now() - INTERVAL 1 DAY
GROUP BY user_id, event_type

Optimize aggregations¶

Use more specific grouping or add LIMIT to aggregations:

SELECT user_id, event_type, COUNT(*) as count
FROM events
GROUP BY user_id, event_type
LIMIT 10000

Use subqueries for large datasets¶

Break down complex queries into smaller parts:

SELECT * FROM (
    SELECT user_id, COUNT(*) as count
    FROM events
    GROUP BY user_id
    LIMIT 1000
) t
WHERE count > 10

Common patterns and solutions¶

Pagination¶

Use LIMIT with OFFSET for pagination:

SELECT * FROM events
ORDER BY timestamp DESC
LIMIT 100 OFFSET 200

Top N queries¶

Use LIMIT for top N results:

SELECT user_id, COUNT(*) as event_count
FROM events
GROUP BY user_id
ORDER BY event_count DESC
LIMIT 10

Sampling large datasets¶

Use SAMPLE for large tables:

SELECT * FROM events SAMPLE 0.01

Time-based filtering¶

Filter by time ranges to reduce data:

SELECT * FROM events
WHERE timestamp >= now() - INTERVAL 1 DAY
LIMIT 1000

Advanced solutions¶

Use approximate functions¶

For large datasets, consider approximate functions:

SELECT uniqHLL(user_id) as approximate_user_count
FROM events

Optimize JOIN operations¶

Use proper JOIN conditions to avoid cartesian products:

SELECT u.user_id, e.event_type
FROM users u
JOIN events e ON u.user_id = e.user_id
LIMIT 1000

Use Materialized Views¶

For frequently accessed aggregations, use Materialized Views:

SELECT * FROM events_daily_stats LIMIT 1000

Tinybird-specific notes¶

In Tinybird, this error often occurs when:

• Querying large Data Sources without proper filtering
• Building Pipes that generate too many intermediate results
• Using Materialized Views that exceed size limits
• Running queries on high-cardinality columns

To debug in Tinybird:

1. Check your Data Source size and add appropriate filters
2. Use the Query Builder to test with LIMIT clauses first
3. Consider breaking large Pipes into smaller nodes
4. Use Materialized Views for pre-aggregated data

Configuration limits¶

You can check and adjust limits in ClickHouse:

SELECT name, value
FROM system.settings
WHERE name LIKE '%max_result%'

Common settings to adjust:

• max_result_rows - maximum number of rows in result
• max_result_bytes - maximum size of result in bytes
• max_block_size - maximum block size for processing

See also¶

• ClickHouse Query Optimization
• Working with Large Datasets
• Common function errors