presto-main/src/main/java/io/prestosql/operator/HashCollisionsInfo.java/HashCollisionsInfo/mergeWith
class HashCollisionsInfo:    @Override
    public HashCollisionsInfo mergeWith(HashCollisionsInfo other)
    {
        return new HashCollisionsInfo(
                this.weightedHashCollisions + other.getWeightedHashCollisions(),
                this.weightedSumSquaredHashCollisions + other.getWeightedSumSquaredHashCollisions(),
                this.weightedExpectedHashCollisions + other.getWeightedExpectedHashCollisions());
    }