1. A computer system for processing a text search query in a collection of documents, comprising: a computer; a full posting index for the documents of the collection, said full posting index comprising a first set of index terms and a full posting list for said index terms of said first set, enumerating all occurrences of said index terms of said first set in all documents of the collection; search conditions on search terms of a given text search query that are translated into conditions on said index terms to provide translated conditions; an additional posting index for said documents of the collection, said additional posting index being related to a defined document part and comprising a second set of index terms and a restricted posting list for said index terms of said second set, enumerating all occurrences of said index terms of said second set in said document part of said documents of said collection; identified conditions of said translated conditions, which are restricted to defined document parts, for which an additional posting index is available; said identified conditions with part restriction rewritten as pair conditions on index terms of said additional posting index and corresponding document part; and a query result based on said additional posting index and said pair conditions.