warn-partition-default-scan

What It Detects

ATTACH PARTITION scans the DEFAULT partition under ACCESS EXCLUSIVE lock to check for overlapping rows.

Why It's Dangerous

When attaching a new partition, PostgreSQL scans the entire DEFAULT partition while holding an ACCESS EXCLUSIVE lock on it. If the default partition is large, this blocks all reads and writes.

Bad Example

ALTER TABLE events ATTACH PARTITION events_2024
  FOR VALUES FROM ('2024-01-01') TO ('2025-01-01');

Good Example

-- Move rows from default partition first, then attach:
SET lock_timeout = '5s';
ALTER TABLE events ATTACH PARTITION events_2024
  FOR VALUES FROM ('2024-01-01') TO ('2025-01-01');
RESET lock_timeout;

Configuration

Disable this rule:

# .migrationpilotrc.yml
rules:
  MP072: false

Or change its severity:

# .migrationpilotrc.yml
rules:
  MP072:
    severity: warning