Lucene: how to boost some specific field

Question

In my case, documents have two fields, for example, "title" and "views". "views" is represented the num of times that people have visited this document. like: "title":"iphone", "views":"10". I have to develop a strategy that will assign some weights to views, such as the relevance score is calculated by score(title)*0.8+score(views)*0.2. Does lucene can do this? And I want to know whether there are some algorithms related to this question.

Answer 1

Here is how you can do that:

Query titleQuery, viewsQuery;

titleQuery.setBoost(0.8);
viewsQuery.setBoost(0.2);
BooleanQuery query = new BooleanQuery();
query.add(titleQuery, Occur.MUST); // or Occur.SHOULD if this clause is optional
query.add(viewsQuery, Occur.SHOULD); // or Occur.MUST if this clause is required

// use query to search documents

The score will be proportional to 0.8*score(titleQuery) + 0.2*score(viewsQuery) (to a multiplicative constant).

To leverage your views field, you will probably need to use a ValueSourceQuery.

Answer 2

You can boost in 3 ways. Depending on your needs you might want to employ a combination

Document level boosting - while indexing - by calling document.setBoost() before a document is added to the index.

Document's Field level boosting - while indexing - by calling field.setBoost() before adding a field to the document (and before adding the document to the index).

Query level boosting - during search, by setting a boost on a query clause, calling Query.setBoost().

source: http://lucene.apache.org/core/old_versioned_docs/versions/3_0_0/scoring.html