ment of such an algorithm is that it minimize the number of random disk
seeks during sorting – sequential disk reads are far faster than seeks as we
explained in Section 4.1. One solution is the blocked sorBLOCKED SORT-BASED t-based indexing algo-
INDEXING ALGORITHM rithmor BSBI in Figure 4.2. BSBI (i) segments the collection into parts of equal
size, (ii) sorts the termID–docID pairs of each part in memory, (iii) stores intermediate
sorted results on disk, and (iv) merges all intermediate results
into the final index.