Computing Scores in a Complete Search System Efficient Ranking Index elimination Basic algorithm FastCosineScore of Fig 7. 1 only considers docs containing at least one query term Take this further. Only consider high-idf query terms Only consider docs containing many query terms
Computing Scores in a Complete Search System Index elimination ▪ Basic algorithm FastCosineScore of Fig 7.1 only considers docs containing at least one query term ▪ Take this further: ▪ Only consider high-idf query terms ▪ Only consider docs containing many query terms Efficient Ranking 16
Computing Scores in a Complete Search System Efficient Ranking High-idf query terms only or a query such as catcher in the rye Only accumulate scores from catcher and rye Intuition in and the contribute little to the scores and so don't alter rank-ordering much Benefit Postings of low-idf terms have many docs >these(many) docs get eliminated from set A of contenders 17
Computing Scores in a Complete Search System High-idf query terms only ▪ For a query such as catcher in the rye ▪ Only accumulate scores from catcher and rye ▪ Intuition: in and the contribute little to the scores and so don’t alter rank-ordering much ▪ Benefit: ▪ Postings of low-idf terms have many docs → these (many) docs get eliminated from set A of contenders Efficient Ranking 17