advanced~4h
N+1 Queries & Fetching Strategies — JOIN FETCH, Entity Graph, Batch Fetch
The single most common real-world Hibernate performance problem, and the highest-leverage skill in this entire course to actually master — one query for N parents, plus N more for each one's lazily-loaded association, fixed by JOIN FETCH, Entity Graphs, or batch fetching.
Learning objectives
- Diagnose an N+1 query problem by reading generated SQL / query counts.
- Fix N+1 using JOIN FETCH, an Entity Graph, or batch fetching, and explain the tradeoff between the three.
- Explain why combining JOIN FETCH with pagination on a one-to-many association produces incorrect results.
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N+1 Queries & Fetching Strategies — JOIN FETCH, Entity Graph, Batch Fetch