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+---
+title: Use Covering Indexes to Avoid Table Lookups
+impact: MEDIUM-HIGH
+impactDescription: 2-5x faster queries by eliminating heap fetches
+tags: indexes, covering-index, include, index-only-scan
+---
+
+## Use Covering Indexes to Avoid Table Lookups
+
+Covering indexes include all columns needed by a query, enabling index-only scans that skip the table entirely.
+
+**Incorrect (index scan + heap fetch):**
+
+```sql
+create index users_email_idx on users (email);
+
+-- Must fetch name and created_at from table heap
+select email, name, created_at from users where email = 'user@example.com';
+```
+
+**Correct (index-only scan with INCLUDE):**
+
+```sql
+-- Include non-searchable columns in the index
+create index users_email_idx on users (email) include (name, created_at);
+
+-- All columns served from index, no table access needed
+select email, name, created_at from users where email = 'user@example.com';
+```
+
+Use INCLUDE for columns you SELECT but don't filter on:
+
+```sql
+-- Searching by status, but also need customer_id and total
+create index orders_status_idx on orders (status) include (customer_id, total);
+
+select status, customer_id, total from orders where status = 'shipped';
+```
+
+Reference: [Index-Only Scans](https://www.postgresql.org/docs/current/indexes-index-only-scans.html)