count
Counts the number of live documents that match a given this.query in a leaf.
The default implementation returns -1 for every query. This indicates that the count could not be computed in sub-linear time.
Specific query classes should override it to provide other accurate sub-linear implementations (that actually return the count). Look at for an example
We use this property of the function to count hits in IndexSearcher.count.
Return
integer count of the number of matches
Parameters
context
the org.gnit.lucenekmp.index.LeafReaderContext for which to return the count.
Throws
IOException
if there is a low-level I/O error