public int getFullResultSets() {
        return fullResultSets;
    }
A Coverage instance contains coverage information for potentially more
than one search. If several queries, e.g. through blending of results
from multiple clusters, produced a result set, this number will show how
many of the result sets for these queries had full coverage.

@return the number of result sets which had full coverage
container-core/src/main/java/com/yahoo/container/handler/Coverage.java