Eager-Loading, Over-Eager loading and Lazy loading

There are three levels:

  1. Eager loading: you do everything when asked. Classic example is when you multiply two matrices. You do all the calculations. That’s eager loading;
  2. Lazy loading: you only do a calculation when required. In the previous example, you don’t do any calculations until you access an element of the result matrix; and
  3. Over-eager loading: this is where you try and anticipate what the user will ask for and preload it.

I hope that makes sense in the context you’re seeing it.

Let me give you a “Webby” example.

Imagine a page with rollover images like for menu items or navigation. There are three ways the image loading could work on this page:

  1. Load every single image required before you render the page (eager);
  2. Load only the displayed images on page load and load the others if/when they are required (lazy); and
  3. Load only the displayed images on page load. After the page has loaded preload the other images in the background in case you need them (over-eager).

Source: http://stackoverflow.com/questions/1299374/what-is-eager-loading

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