if (firstValidCG >= 0) {
List<CGRangeSplit> cgSplits = colGroups[firstValidCG].rangeSplit(n);
int numSlices = cgSplits.size();
ret = new ArrayList<RangeSplit>(numSlices);
for (int slice = 0; slice < numSlices; slice++) {
CGRangeSplit oneSliceSplit = cgSplits.get(slice);
ret.add(new BasicTable.Reader.RangeSplit(oneSliceSplit));
}
return ret;
} else { // all column groups are dropped.
ret = new ArrayList<RangeSplit>(1);
// add a dummy split
ret.add(new BasicTable.Reader.RangeSplit(new CGRangeSplit(0, 0)));
return ret;
}
}