Patent ID: 7689574

Claim:
A computer-implemented method of extending an inverted index, the inverted index comprising a first inverted index subfile and a second inverted index subfile, the method comprising: performing, by a computer, ordered keyword indexing operations of generating an inverted index from one or more data sources in the memory, wherein ordered keyword indexing operations comprise: calculating a frequency of occurrence of keywords in each of the one or more data sources; and writing each keyword, the one or more data sources corresponding to each keyword, and the frequency of occurrence of each keyword in the corresponding one or more data sources to the inverted index; if a number of data sources involved in the indexing operations reaches a first threshold value, k1, then writing, by said computer, contents of the inverted index as a smallest grid into the first inverted index subfile, until said number of data sources equals k1, otherwise returning to the performing ordered keyword indexing operations; if a number of smallest grids in the first inverted index subfile reaches a second threshold value, k2, then merging, by said computer, the k2 smallest grids into a merged grid and writing the merged grid into the second inverted index subfile, until said number of smallest grids equals k 2 , otherwise, returning to the performing ordered keyword indexing operations; and if the number of merged grids in the second inverted index subfile reaches a third threshold value, k3, then further merging, by said computer, the merged k3 grids into a larger merged grid, writing the larger merged grid into the first inverted index subfile, and returning to the merging of the k2 smallest grids into a merged grid and writing the merged grid into the second inverted index subfile, until said number of merged grids equal k 3 , otherwise, returning to the performing indexing operations.