Lazy Loading

What is Lazy Loading

Lazy Loading loads the associated entity when you actually use it, also called a delayed loading.

Features

  • It fetches associated data when it is actually being used, not immediately.
  • It is used to optimize performance and to reduce memory usage.
  • It reduces the initial loading time when there are many associated entities.

Example

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@OneToMany(fetch = FetchType.LAZY)
private List<Order> orders;

Advantages

  • Reduces initial loading time.
  • Can reduce memory usage when there are many associated entities.

Disadvantages

  • May cause performance degradation as it fires queries every time a part of the associated entity is used.

Eager Loading

What is Eager Loading

Eager Loading is a way to load the associated entity together when the entity is fetched, it is also called an immediate loading.

Features

  • It fetches associated data all at once when the entity is fetched.
  • There is no need to execute additional queries when using the associated entities.
  • It does not cause the N+1 problem.

Example

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@OneToMany(fetch = FetchType.EAGER)
private List<Order> orders;

Advantages

  • No need to execute additional queries when using the associated entities.

Disadvantages

  • May increase the initial loading time.
  • Can increase memory usage when there are many associated entities.

Summary

  • Lazy Loading is a way of loading associated entities when they are actually used.
  • Eager Loading is a way of loading associated entities together when the entity is fetched.
  • Lazy Loading can reduce the initial loading time and memory usage, while Eager Loading eliminates the need for additional queries when using associated entities.