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+---
+title: Use Partial Indexes for Filtered Queries
+impact: HIGH
+impactDescription: 5-20x smaller indexes, faster writes and queries
+tags: indexes, partial-index, query-optimization, storage
+---
+
+## Use Partial Indexes for Filtered Queries
+
+Partial indexes only include rows matching a WHERE condition, making them smaller and faster when queries consistently filter on the same condition.
+
+**Incorrect (full index includes irrelevant rows):**
+
+```sql
+-- Index includes all rows, even soft-deleted ones
+create index users_email_idx on users (email);
+
+-- Query always filters active users
+select * from users where email = 'user@example.com' and deleted_at is null;
+```
+
+**Correct (partial index matches query filter):**
+
+```sql
+-- Index only includes active users
+create index users_active_email_idx on users (email)
+where deleted_at is null;
+
+-- Query uses the smaller, faster index
+select * from users where email = 'user@example.com' and deleted_at is null;
+```
+
+Common use cases for partial indexes:
+
+```sql
+-- Only pending orders (status rarely changes once completed)
+create index orders_pending_idx on orders (created_at)
+where status = 'pending';
+
+-- Only non-null values
+create index products_sku_idx on products (sku)
+where sku is not null;
+```
+
+Reference: [Partial Indexes](https://www.postgresql.org/docs/current/indexes-partial.html)