/**
* Coalesce sort groups that have compatible partition-by exprs and have a prefix relationship.
*/
private void mergeSortGroups(List<SortGroup> sortGroups) {
boolean hasMerged = false;
do {
hasMerged = false;
for (SortGroup sg1 : sortGroups) {
for (SortGroup sg2 : sortGroups) {
if (sg1 != sg2 && sg1.isPrefixOf(sg2)) {
sg1.absorb(sg2);
sortGroups.remove(sg2);
hasMerged = true;
break;
}
}
if (hasMerged) break;
}
} while (hasMerged);
}
