Methods and systems are disclosed using linear expressions for machine learning (ML) models for ranking search results. In one example, a method for a computer trains a ML model into a decision tree for ranking search results. The decision tree is converted into a linear expression including Boolean terms. The linear expression is transmitted to one or more search computers that use the linear expression to rank search results for a search query. According to another example, a method for a computer having a search engine includes receiving a linear expression including Boolean terms representing a decision tree. The search engine processes a search query and uses the linear expression to rank search results for the search query.