Hi, We discuss some topic from https://github.com/apache/lucene-solr/pull/595. As Atri Sharma propose discuss with the java dev list.
Impact `frequency ` and `norm ` just to accelerate the `score process` which `terminate early`. In impact mode, `CompetitiveImpactAccumulator` will record (freq, norm) pair , would stored at index level. Also I noted `CompetitiveImpactAccumulator` commented with `This class accumulates the (freq, norm) pairs that may produce competitive scores`, maybe related to `WAND`? The norm value which produced or consumed by `Lucene80NormsFormat`. In this ` Impact way`, we can avoid read norms from `Lucene80NormsProducer` that may generate the extra IO? （ the norm value Lucene stored twice.）and take full advantage of the WAND method?
