List<Pair<String, String>> ranges;
if (this.getConcurrencyLevel() != null) {
ranges = Lists.newArrayList();
int nThreads = this.getConcurrencyLevel();
List<TokenRange> tokens = partitioner.splitTokenRange(
startToken == null ? partitioner.getMinToken() : startToken,
endToken == null ? partitioner.getMaxToken() : endToken,
nThreads);
for (TokenRange range : tokens) {
try {