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+---
+title: Create Composite Indexes for Multi-Column Queries
+impact: HIGH
+impactDescription: 5-10x faster multi-column queries
+tags: indexes, composite-index, multi-column, query-optimization
+---
+
+## Create Composite Indexes for Multi-Column Queries
+
+When queries filter on multiple columns, a composite index is more efficient than separate single-column indexes.
+
+**Incorrect (separate indexes require bitmap scan):**
+
+```sql
+-- Two separate indexes
+create index orders_status_idx on orders (status);
+create index orders_created_idx on orders (created_at);
+
+-- Query must combine both indexes (slower)
+select * from orders where status = 'pending' and created_at > '2024-01-01';
+```
+
+**Correct (composite index):**
+
+```sql
+-- Single composite index (leftmost column first for equality checks)
+create index orders_status_created_idx on orders (status, created_at);
+
+-- Query uses one efficient index scan
+select * from orders where status = 'pending' and created_at > '2024-01-01';
+```
+
+**Column order matters** - place equality columns first, range columns last:
+
+```sql
+-- Good: status (=) before created_at (>)
+create index idx on orders (status, created_at);
+
+-- Works for: WHERE status = 'pending'
+-- Works for: WHERE status = 'pending' AND created_at > '2024-01-01'
+-- Does NOT work for: WHERE created_at > '2024-01-01' (leftmost prefix rule)
+```
+
+Reference: [Multicolumn Indexes](https://www.postgresql.org/docs/current/indexes-multicolumn.html)