* a) "adjacent" to each other;
* b) combined size cannot be more than the threshold
*/
if (prevPair.getSecond() + gapsize < outputValue.getFirst() ||
outputValue.getSecond() - prevPair.getFirst() > maxBlockSize) {
context.write(new TextLongPairWritable(new Text(columnValue), prevPair.getFirst()), prevPair);
if (LOG.isDebugEnabled()) {
LOG.debug("write to reducer: " + prevPair);
}
map.put(columnValue, new LongPairWritable(outputValue));