How to use

deduceCollations

method

in

org.apache.calcite.rex.RexProgram

/**
 * Given a list of collations which hold for the input to this program,
 * returns a list of collations which hold for its output. The result is
 * mutable and sorted.
 */
public List<RelCollation> getCollations(List<RelCollation> inputCollations) {
 final List<RelCollation> outputCollations = new ArrayList<>();
 deduceCollations(
   outputCollations,
   inputRowType.getFieldCount(), projects,
   inputCollations);
 return outputCollations;
}

/**
 * Given a list of collations which hold for the input to this program,
 * returns a list of collations which hold for its output. The result is
 * mutable and sorted.
 */
public List<RelCollation> getCollations(List<RelCollation> inputCollations) {
 final List<RelCollation> outputCollations = new ArrayList<>();
 deduceCollations(
   outputCollations,
   inputRowType.getFieldCount(), projects,
   inputCollations);
 return outputCollations;
}