Document treadmilling system and method for updating documents in a document repository and recovering storage space from invalidated documents A tokenspace repository stores documents as a sequence of tokens. The tokenspace repository, as well as the inverted index for the tokenspace repository, uses a data structure that has a first end and a second end and allows for insertions at the second end and deletions from the front end. A document in the tokenspace repository is updated by inserting the updated version into the repository at the second end and invalidating the earlier version. Invalidated documents are not deleted immediately; they are identified in a garbage collection list for later … Continue reading Michael Burrows, Jeffrey A. Dean