background
So much internal data structure, as it is made redis data structure, purpose is to save memory and speed.
Because these data structures, other places are not presented, including algorithms book.
In summary, the internal and external data structure is a separate data structure, independent. Internal data structure is one way of implementing the external data structures, like linked lists a variety of implementations.
Reproduced in: https: //juejin.im/post/5cf33691f265da1b9253c3a6