1. A system for providing full-text search integration in XQuery, comprising: a storage device storing computer-executable program code; a processor executing the computer-executable program code in computer-executable program modules, comprising: an XQuery interpreter implementing a built-in search function defined in an XQuery language and initiating a full-text search, wherein the search function comprises one or more search terms and a relation logic; a search function implementation module identifying variants for each search term comprised in the search function and obtaining posting lists for one or more of the variants, each posting list comprising values offset from elements containing the search term associated with the variant to which the posting list corresponds; a postings resolution module applying the relation logic to the offset values of the posting lists and selecting those elements with offset values that satisfy the relation logic; and a posting module providing the elements that satisfy the relation logic to the XQuery interpreter as results of the full-text search.