N+1 Query Problem

Definitions

1. A performance anti-pattern where code executes 1 query to fetch a list of N items, then N additional queries to fetch related data for each item. Common with ORMs that use lazy loading. Fixed with eager loading (JOIN), batch loading, or dataloaders.

   In plain English: Accidentally making hundreds of database queries when one or two would do, usually because of how an ORM loads related data.

   Example: "The page was making 201 queries — 1 for the 200 users and 1 each for their profile photos. Classic N+1 problem."

Related Terms

• Ecto
• Connection Pooling
• Query Plan
• Index Scan vs Seq Scan
• Partitioning
• Join Table
• Query Builder
• Query Cache
• Query Optimizer
• SQLAlchemy
• TypeORM