This invention relates to an inverted index storage structure that indexes keyword inputs into the storage space for the corresponding posting lists. In particular, the invention relates to the index structure that enables fast retrieval of the posting of the specific document from the posting list and enables efficient arrangement and maintenance of the posting list in document identifier (docID) order, so that fast addition, deletion, modification, and retrieval of documents are possible in environments where a database management system is tightly coupled with information retrieval. The technical solution is to store the posting list in a large object and map to each posting list a subindex that indexes the docID into the postings containing the docID.