1. A search ranking method suitable for a file system, comprising: receiving a query; calculating final relevance scores of individual file items with respect to said query at least partially in accordance with energy scores of individual nodes on a current file system energy tree, and outputting a list of search results based on said final relevance scores; and updating said file system energy tree in response to an operation on said file system performed by a user, wherein said file system energy tree has a tree structure corresponding to that of said file system, and said individual nodes thereof respectively correspond to the individual file items in said file system.