presto-ml/src/main/java/io/prestosql/plugin/ml/EvaluateClassifierPredictionsAggregation.java/EvaluateClassifierPredictionsAggregation/mergeMaps
class EvaluateClassifierPredictionsAggregation:    private static int mergeMaps(Map<String, Integer> map, Map<String, Integer> other)
    {
        int deltaSize = 0;
        for (Map.Entry<String, Integer> entry : other.entrySet()) {
            if (!map.containsKey(entry.getKey())) {
                deltaSize += entry.getKey().getBytes(UTF_8).length + SIZE_OF_INT;
            }
            map.put(entry.getKey(), map.getOrDefault(entry.getKey(), 0) + other.getOrDefault(entry.getKey(), 0));
        }
        return deltaSize;
    }