1---
2title: Use Covering Indexes to Avoid Table Lookups
3impact: MEDIUM-HIGH
4impactDescription: 2-5x faster queries by eliminating heap fetches
5tags: indexes, covering-index, include, index-only-scan
6---
7 
8## Use Covering Indexes to Avoid Table Lookups
9 
10Covering indexes include all columns needed by a query, enabling index-only scans that skip the table entirely.
11 
12**Incorrect (index scan + heap fetch):**
13 
14```sql
15create index users_email_idx on users (email);
16 
17-- Must fetch name and created_at from table heap
18select email, name, created_at from users where email = '[email protected]';
19```
20 
21**Correct (index-only scan with INCLUDE):**
22 
23```sql
24-- Include non-searchable columns in the index
25create index users_email_idx on users (email) include (name, created_at);
26 
27-- All columns served from index, no table access needed
28select email, name, created_at from users where email = '[email protected]';
29```
30 
31Use INCLUDE for columns you SELECT but don't filter on:
32 
33```sql
34-- Searching by status, but also need customer_id and total
35create index orders_status_idx on orders (status) include (customer_id, total);
36 
37select status, customer_id, total from orders where status = 'shipped';
38```
39 
40Reference: [Index-Only Scans](https://www.postgresql.org/docs/current/indexes-index-only-scans.html)
41