private List<RelCollation> deduceMonotonicity(SqlValidatorTable table) {
final RelDataType rowType = table.getRowType();
final List<RelCollation> collationList = new ArrayList<RelCollation>();
// Deduce which fields the table is sorted on.
int i = -1;
for (RelDataTypeField field : rowType.getFieldList()) {
++i;
final SqlMonotonicity monotonicity = table.getMonotonicity(field.getName());
if (monotonicity != SqlMonotonicity.NOT_MONOTONIC) {
final RelFieldCollation.Direction direction =
monotonicity.isDecreasing()
? RelFieldCollation.Direction.DESCENDING
: RelFieldCollation.Direction.ASCENDING;
collationList.add(
RelCollationImpl.of(
new RelFieldCollation(
i, direction, RelFieldCollation.NullDirection.UNSPECIFIED)));
}
}
return collationList;
}
