how lucene use skip list in inverted index?

Question

In some blogs and lucene website,I know lucene use data structure \"skip list\" in inverted index. But I have some puzzle about it.

1:In general,skip list maybe use

Answer 1

see To accelerate posting list skips, Lucene uses skip lists

Answer 2

Lucene uses memory in a couple different ways, even though the index is persisted on a disk when the IndexReader is created for searching and for operations like sorting (field cache):

http://blog.mikemccandless.com/2010/07/lucenes-ram-usage-for-searching.html

Basically those binary files get copied into RAM for much faster scanning and reducing I/O. You get a hint in the above link how searching with some parameters can force Lucene to "skip terms in searching" Hence, where that data structure can be used.

Lucene is open source, so you can see the code for yourself what is being used in Java or Lucene.NET for the C# implementation.