Index-Only Scans Disabled | PG Pilot PostgreSQL Monitoring

What is this issue?

Index-only scans allow PostgreSQL to answer queries entirely from the
index without reading the table (heap). This is possible when:

- All required columns are in the index
- The visibility map shows pages are all-visible

With enable_indexonlyscan = off:
- Always fetches from heap even when unnecessary
- 2-10x slower for covered queries
- More I/O than needed

This is a significant performance optimization to lose.

Index-only scans are dramatically faster

Reading heap when index has all data

INCLUDE columns provide no benefit

Loading heap pages that aren't needed

```sql
SELECT name, setting
FROM pg_settings
WHERE name = 'enable_indexonlyscan';
```

1

ALTER SYSTEM SET enable_indexonlyscan = on;
SELECT pg_reload_conf();

2

Check for "Index Only Scan" in plans:

EXPLAIN SELECT id, name FROM users WHERE id = 1;

3

VACUUM updates the visibility map:

VACUUM your_table;