Troubleshooting guide

This guide covers potential errors and limitations you may encounter when using R2 SQL. R2 SQL is in open beta, and supported functionality will evolve and change over time.

Query structure errors

Missing required clauses

Error: expected exactly 1 table in FROM clause

Problem: R2 SQL requires a FROM clause in your query.

-- Invalid - Missing FROM clause
SELECT user_id WHERE status = 200;

-- Valid
SELECT user_id
FROM my_namespace.http_requests
WHERE status = 200 AND timestamp BETWEEN '2025-09-24T01:00:00Z' AND '2025-09-25T01:00:00Z';

Solution: Always include FROM with a fully qualified table name (namespace_name.table_name).

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FROM clause issues

Multiple tables

Error: unsupported feature: JOIN operations are not supported

Problem: R2 SQL queries reference exactly one table. JOINs and multiple tables are not supported.

-- Invalid - Multiple tables not supported
SELECT a.*, b.* FROM my_namespace.table1 a, my_namespace.table2 b WHERE a.id = b.id
SELECT * FROM my_namespace.events JOIN my_namespace.users ON events.user_id = users.id

-- Valid - Separate queries
SELECT * FROM my_namespace.table1 WHERE id IN ('id1', 'id2', 'id3') LIMIT 100
-- Then query the second table separately in your application
SELECT * FROM my_namespace.table2 WHERE id IN ('id1', 'id2', 'id3') LIMIT 100

Solution:

• Denormalize your data by including necessary fields in a single table.
• Perform multiple queries and join data in your application.

Subqueries

Error: unsupported feature: subqueries

Problem: Subqueries in FROM, WHERE, and scalar positions are not supported.

-- Invalid - Subqueries not supported
SELECT * FROM (SELECT user_id FROM my_namespace.events WHERE status = 200)

-- Valid - Use direct query with appropriate filters
SELECT user_id FROM my_namespace.events WHERE status = 200 LIMIT 100

Solution: Flatten your query logic or use multiple sequential queries.

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WHERE clause issues

JSON object filtering

Error: unsupported binary operator or Error during planning: could not parse compound

Problem: JSON functions are not yet implemented. You cannot filter on fields inside JSON objects using JSON path operators.

-- Invalid - JSON path operators not supported
SELECT * FROM my_namespace.requests WHERE json_data->>'level' = 'error'

-- Valid - Filter on the entire JSON column
SELECT * FROM my_namespace.logs WHERE json_data IS NOT NULL LIMIT 100

Solution:

• Denormalize frequently queried JSON fields into separate columns.
• Filter on the entire JSON field, and handle parsing in your application.

Note

Struct columns are supported and can be filtered using bracket notation. Refer to Complex types for details.

SELECT * FROM my_namespace.products WHERE pricing['price'] > 50 LIMIT 100

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LIMIT clause issues

Invalid limit values

Error: maximum LIMIT is 10000

Problem: LIMIT values must be between 1 and 10,000.

-- Invalid - Out of range
SELECT * FROM my_namespace.events LIMIT 50000

-- Valid
SELECT * FROM my_namespace.events LIMIT 10000

Solution: Use LIMIT values between 1 and 10,000.

Pagination attempts

Error: unsupported feature: OFFSET clause is not supported

Problem: OFFSET is not supported.

-- Invalid - Pagination not supported
SELECT * FROM my_namespace.events LIMIT 100 OFFSET 200

-- Valid - Use cursor-based pagination with ORDER BY and WHERE
-- Page 1
SELECT * FROM my_namespace.events
WHERE timestamp >= '2024-01-01'
ORDER BY timestamp
LIMIT 100

-- Page 2 - Use the last timestamp from the previous page
SELECT * FROM my_namespace.events
WHERE timestamp > '2024-01-01T10:30:00Z'
ORDER BY timestamp
LIMIT 100

Solution: Implement cursor-based pagination using ORDER BY and WHERE conditions.

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Schema issues

DDL and DML operations

Error: only read-only queries are allowed

Problem: R2 SQL is a read-only query engine. DDL and DML statements are not supported.

-- Invalid - Schema changes not supported
ALTER TABLE my_namespace.events ADD COLUMN new_field STRING
UPDATE my_namespace.events SET status = 200 WHERE user_id = '123'
CREATE TABLE my_namespace.test (id INT)
DROP TABLE my_namespace.events

Solution: Manage your schema through your data ingestion pipeline and R2 Data Catalog.

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Performance optimization

Query performance issues

If your queries are running slowly:

1. Always include partition (timestamp) filters: This is the most important optimization.

   -- Good - Narrows data scan to one day
   SELECT * FROM my_namespace.events
   WHERE timestamp BETWEEN '2024-01-01' AND '2024-01-02'
   LIMIT 100

2. Use selective filtering: Include specific conditions to reduce result sets.

   -- Good - Multiple filters reduce scanned data
   SELECT * FROM my_namespace.events
   WHERE status = 200 AND region = 'US' AND timestamp > '2024-01-01'
   LIMIT 100

3. Select specific columns: Avoid SELECT * when you only need a few fields.

   -- Good - Only reads the columns you need
   SELECT user_id, status, timestamp
   FROM my_namespace.events
   WHERE timestamp > '2024-01-01'
   LIMIT 100

4. Use EXPLAIN to inspect the execution plan: Verify that predicate pushdown and file pruning are working.

   EXPLAIN SELECT user_id, status
   FROM my_namespace.events
   WHERE timestamp > '2024-01-01' AND status = 200

5. Enable compaction: Enable compaction in R2 Data Catalog to reduce the number of small files scanned per query.