public void onLoad(FieldMapper.Names fieldNames, FieldDataType fieldDataType, Accountable ramUsage) {
totalMetric.inc(ramUsage.ramBytesUsed());
String keyFieldName = fieldNames.indexName();
CounterMetric total = perFieldTotals.get(keyFieldName);
if (total != null) {
total.inc(ramUsage.ramBytesUsed());
} else {
total = new CounterMetric();
total.inc(ramUsage.ramBytesUsed());
CounterMetric prev = perFieldTotals.putIfAbsent(keyFieldName, total);
if (prev != null) {