1. A method performed on a computing device that includes at least one processor and memory, the method comprising: maintaining, by the computing device, an index that comprises tokens that correspond to words that are included in a file in a storage; receiving, by the computing device, an event associated with a change to the file, the change corresponding to one of deleting a word from the file, or adding a word to the file; determining, by the computing device, whether the file is located in a protected namespace; adding, by the computing device to the index, a token for an added word when the change corresponds to a word being added to the file; retaining, by the computing device in the index, a token for a deleted word when the change corresponds to a word being deleted from the file, wherein the retained token corresponds to the deleted word; and for a file in the protected namespace, maintaining, by the computing device in the index, tokens for added words and deleted words subsequent to the file in the protected namespace being deleted from the storage, wherein the maintained tokens correspond to the added and deleted words.