// NewTopNCollector builds a collector to find the top 'size' hits
// skipping over the first 'skip' hits
// ordering hits by the provided sort order
func NewTopNCollector(size int, skip int, sort search.SortOrder) *TopNCollector {
hc := &TopNCollector{size: size, skip: skip, sort: sort}
// pre-allocate space on the store to avoid reslicing
// unless the size + skip is too large, then cap it
// everything should still work, just reslices as necessary
backingSize := size + skip + 1
if size+skip > PreAllocSizeSkipCap {
backingSize = PreAllocSizeSkipCap + 1
}
hc.store = newStoreSlice(backingSize, func(i, j *search.DocumentMatch) int {
return hc.sort.Compare(hc.cachedScoring, hc.cachedDesc, i, j)
})
// these lookups traverse an interface, so do once up-front
if sort.RequiresDocID() {
hc.needDocIds = true
}
hc.neededFields = sort.RequiredFields()
hc.cachedScoring = sort.CacheIsScore()
hc.cachedDesc = sort.CacheDescending()
return hc
}
func newMultiSearchHitSorter(sort search.SortOrder, hits search.DocumentMatchCollection) *multiSearchHitSorter {
return &multiSearchHitSorter{
sort: sort,
hits: hits,
cachedScoring: sort.CacheIsScore(),
cachedDesc: sort.CacheDescending(),
}
}