A method and system for selecting documents for inclusion into a search engine search index executed by a machine learning algorithm (MLA) comprising: acquiring a plurality of digital documents, each respective document having a respective size, determining a respective value parameter based on user interactions, ranking the digital documents to obtain a ranked list of documents based on: a respective quality value parameter based on the respective value parameter and the respective size, the ranking being performed such that a cumulative quality value parameter is maximized based on: the quality value parameter of a given digital document is weighted by a sum of the sizes of a given subset of documents, wherein the given subset consists of documents having a respective value parameter below the value parameter of the given digital document, selecting a subset from the ranked list and storing the subset in the search index.