Have you ever searched for something and found a link that wasn't quite what you were looking for but was reasonably close? If you were using an Internet search engine such as Google, then you may have tried the "more like this…" link next to a search result. Some sites use other language like "find similar..." or "related documents…" As these links suggest, they show you pages similar to another page. Solr supports more like this (MLT) too.
The MLT capability in Solr can be used in the following three ways:
As a search component: The MLT search component performs MLT analysis on each document returned in a search. This is not usually desired and so it is rarely used.
As a request handler: The MLT request handler gives MLT results that are based on a specific indexed document. This is commonly used in reaction to a user clicking a "more like this" link on existing search results. The key input to this option is a reference to the indexed document that you want similar...