Blocked sort-based indexing has excellent scaling properties, but it needs a data structure for mapping terms to termIDs. For very large collections, this data structure does not fit into memory. A more scalable alternative is single-pass in-memory indexing or SPIMI. SPIMI uses terms instead of termIDs,writ eseach block’s dictionary to disk, and then starts a new dictionary for the next block. SPIMI can index collections of any size as long as there is enough disk space available.