In
computer science, an
inverted index (also referred to as
postings file or
inverted file) is an
index data structure storing a mapping from content, such as words or numbers, to its locations in a
database file, or in a document or a set of documents (named in contrast to a
Forward Index, which maps from documents to content). The purpose of an inverted index is to allow fast
full text searches, at a cost of increased processing when a document is added to the database. The inverted file may be the database file itself, rather than its
index. It is the most popular data structure used in
document retrieval systems, used on a large scale for example in
search engines. Additionally, several significant general-purpose
mainframe-based
database management systems have used inverted list architectures, including
ADABAS,
DATACOM/DB, and
Model 204.