R2 SQL Gotchas

Limitations, troubleshooting, and common pitfalls for R2 SQL.

Critical Limitations

No Workers Binding

Cannot call R2 SQL from Workers/Pages code - no binding exists.

// ❌ This doesn't exist

  async fetch(request, env) {
    const result = await env.R2_SQL.query("SELECT * FROM table");  // Not possible
    return Response.json(result);
  }
};

Solutions:

• HTTP API from external systems (not Workers)
• PyIceberg/Spark via r2-data-catalog REST API
• For Workers, use D1 or external databases

ORDER BY Limitations

Can only order by:

1. Partition key columns - Always supported
2. Aggregation functions - Supported via shuffle strategy

Cannot order by regular non-partition columns.

-- ✅ Valid: ORDER BY partition key
SELECT * FROM logs.requests ORDER BY timestamp DESC LIMIT 100;

-- ✅ Valid: ORDER BY aggregation
SELECT region, SUM(amount) FROM sales.transactions
GROUP BY region ORDER BY SUM(amount) DESC;

-- ❌ Invalid: ORDER BY non-partition column
SELECT * FROM logs.requests ORDER BY user_id;

-- ❌ Invalid: ORDER BY alias (must repeat function)
SELECT region, SUM(amount) as total FROM sales.transactions
GROUP BY region ORDER BY total;  -- Use ORDER BY SUM(amount)

Check partition spec: DESCRIBE namespace.table_name

SQL Feature Limitations

Workarounds:

• No JOINs: Denormalize data or use Spark/PyIceberg
• No subqueries: Split into multiple queries
• No aliases: Accept generated names, transform in app

Common Errors

"Column not found"

Cause: Typo, column doesn't exist, or case mismatch
Solution: DESCRIBE namespace.table_name to check schema

"Type mismatch"

-- ❌ Wrong types
WHERE status = '200'              -- string instead of integer
WHERE timestamp > '2025-01-01'    -- missing time/timezone

-- ✅ Correct types
WHERE status = 200
WHERE timestamp > '2025-01-01T00:00:00Z'

"ORDER BY column not in partition key"

Cause: Ordering by non-partition column
Solution: Use partition key, aggregation, or remove ORDER BY. Check: DESCRIBE table

"Token authentication failed"

# Check/set token
echo $WRANGLER_R2_SQL_AUTH_TOKEN

# Or .env file
echo "WRANGLER_R2_SQL_AUTH_TOKEN=<your-token>" > .env

"Table not found"

-- Verify catalog and tables
SHOW DATABASES;
SHOW TABLES IN namespace_name;

Enable catalog: npx wrangler r2 bucket catalog enable <bucket>

"LIMIT exceeds maximum"

Max LIMIT is 10,000. For pagination, use WHERE filters with partition keys.

"No data returned" (unexpected)

Debug steps:

1. SELECT COUNT(*) FROM table - verify data exists
2. Remove WHERE filters incrementally
3. SELECT * FROM table LIMIT 10 - inspect actual data/types

Performance Issues

Slow Queries

Causes: Too many partitions, large LIMIT, no filters, small files

-- ❌ Slow: No filters
SELECT * FROM logs.requests LIMIT 10000;

-- ✅ Fast: Filter on partition key
SELECT * FROM logs.requests 
WHERE timestamp >= '2025-01-15T00:00:00Z' AND timestamp < '2025-01-16T00:00:00Z'
LIMIT 1000;

-- ✅ Faster: Multiple filters
SELECT * FROM logs.requests 
WHERE timestamp >= '2025-01-15T00:00:00Z' AND status = 404 AND method = 'GET'
LIMIT 1000;

File optimization:

• Target Parquet size: 100-500MB compressed
• Pipelines roll interval: 300+ sec (prod), 10 sec (dev)
• Run compaction to merge small files

Query Timeout

Solution: Add restrictive WHERE filters, reduce time range, query smaller intervals

-- ❌ Times out: Year-long aggregation
SELECT status, COUNT(*) FROM logs.requests 
WHERE timestamp >= '2024-01-01T00:00:00Z' GROUP BY status;

-- ✅ Faster: Month-long aggregation
SELECT status, COUNT(*) FROM logs.requests 
WHERE timestamp >= '2025-01-01T00:00:00Z' AND timestamp < '2025-02-01T00:00:00Z'
GROUP BY status;

Best Practices

Partitioning

• Time-series: Partition by day/hour on timestamp
• Avoid: High-cardinality keys (user_id), >10,000 partitions

from pyiceberg.partitioning import PartitionSpec, PartitionField
from pyiceberg.transforms import DayTransform

PartitionSpec(PartitionField(source_id=1, field_id=1000, transform=DayTransform(), name="day"))

Query Writing

• Always use LIMIT for early termination
• Filter on partition keys first for pruning
• Combine filters with AND for more pruning

-- Good
WHERE timestamp >= '2025-01-15T00:00:00Z' AND status = 404 AND method = 'GET' LIMIT 100

Type Safety

• Quote strings: 'GET' not GET
• RFC3339 timestamps: '2025-01-01T00:00:00Z' not '2025-01-01'
• ISO dates: '2025-01-15' not '01/15/2025'

Data Organization

• Pipelines: Dev roll_file_time: 10, Prod roll_file_time: 300+
• Compression: Use zstd
• Maintenance: Compaction for small files, expire old snapshots

Debugging Checklist

1. npx wrangler r2 bucket catalog enable <bucket> - Verify catalog
2. echo $WRANGLER_R2_SQL_AUTH_TOKEN - Check token
3. SHOW DATABASES - List namespaces
4. SHOW TABLES IN namespace - List tables
5. DESCRIBE namespace.table - Check schema
6. SELECT COUNT(*) FROM namespace.table - Verify data
7. SELECT * FROM namespace.table LIMIT 10 - Test simple query
8. Add filters incrementally

See Also

• api.md - SQL syntax
• patterns.md - Query optimization
• configuration.md - Setup
• Cloudflare R2 SQL Docs