Facebook has bolstered its search function by indexing 2 trillion posts in a move designed to attack Google's core business and challenge Twitter's news product. The move will allow users to search for topics and be given a bunch of public posts dating back to Facebook's inception. "With over 1.5 billion searches per day and over 2 trillion posts in our index, search is an important, long-term effort at Facebook," Tom Stocky, the social networking giant's vice president of search, said in a blog post on Thursday. "When something happens in the world, people often turn to Facebook to see how their friends and family are reacting. Today, we're updating Facebook Search so that in addition to friends and family, you can find out what the world is saying about topics that matter to you."

By encouraging users to search on the social network rather than through a search engine, Facebook move pitches it into a turf war with Google. It is also challenging Twitter's recently launched "Moments" feature -- a feed that allows users to see the biggest stories of the day through tweets, pictures and videos. Search results will be personalized, according to Facebook, which added that you will be able to find public conversations around a widely shared link, for example, as well as check out an "aggregate overview of sentiment".