Index Compression Dictionary Compression Compressing the term list Dictionary-as-a-String Store dictionary as a(long) string of characters . Pointer to next word shows end of current word .Hope to save up to 60%of dictionary space systilesyzygeticsyzygialsyzygyszaibelyiteszczecinszomo eg Postings ptr. Term ptr. Total string length 400Kx8B=3.2MB 29 44 Pointers resolve 3.2M 126 positions: log232M 22bits= bytesIndex Compression 21 Compressing the term list: Dictionary-as-a-String ….systilesyzygeticsyzygialsyzygyszaibelyiteszczecinszomo…. Freq. Postings ptr. Term ptr. 33 29 44 126 Total string length = 400K x 8B = 3.2MB Pointers resolve 3.2M positions: log23.2M = 22bits = 3bytes ◼Store dictionary as a (long) string of characters: ◼Pointer to next word shows end of current word ◼Hope to save up to 60% of dictionary space. Dictionary Compression