How to use

defaultNullDirection

method

in

org.apache.calcite.sql.SqlDialect

/** Converts a collation to an ORDER BY item. */
public SqlNode toSql(RelFieldCollation collation) {
 SqlNode node = field(collation.getFieldIndex());
 switch (collation.getDirection()) {
 case DESCENDING:
 case STRICTLY_DESCENDING:
  node = SqlStdOperatorTable.DESC.createCall(POS, node);
 }
 if (collation.nullDirection != dialect.defaultNullDirection(collation.direction)) {
  switch (collation.nullDirection) {
  case FIRST:
   node = SqlStdOperatorTable.NULLS_FIRST.createCall(POS, node);
   break;
  case LAST:
   node = SqlStdOperatorTable.NULLS_LAST.createCall(POS, node);
   break;
  }
 }
 return node;
}

/** Converts a collation to an ORDER BY item. */
public SqlNode toSql(RelFieldCollation collation) {
 SqlNode node = field(collation.getFieldIndex());
 switch (collation.getDirection()) {
 case DESCENDING:
 case STRICTLY_DESCENDING:
  node = SqlStdOperatorTable.DESC.createCall(POS, node);
 }
 if (collation.nullDirection != dialect.defaultNullDirection(collation.direction)) {
  switch (collation.nullDirection) {
  case FIRST:
   node = SqlStdOperatorTable.NULLS_FIRST.createCall(POS, node);
   break;
  case LAST:
   node = SqlStdOperatorTable.NULLS_LAST.createCall(POS, node);
   break;
  }
 }
 return node;
}

private SqlNode toSql(RexProgram program, RexFieldCollation rfc) {
 SqlNode node = toSql(program, rfc.left);
 switch (rfc.getDirection()) {
 case DESCENDING:
 case STRICTLY_DESCENDING:
  node = SqlStdOperatorTable.DESC.createCall(POS, node);
 }
 if (rfc.getNullDirection()
     != dialect.defaultNullDirection(rfc.getDirection())) {
  switch (rfc.getNullDirection()) {
  case FIRST:
   node = SqlStdOperatorTable.NULLS_FIRST.createCall(POS, node);
   break;
  case LAST:
   node = SqlStdOperatorTable.NULLS_LAST.createCall(POS, node);
   break;
  }
 }
 return node;
}

private SqlNode toSql(RexProgram program, RexFieldCollation rfc) {
 SqlNode node = toSql(program, rfc.left);
 switch (rfc.getDirection()) {
 case DESCENDING:
 case STRICTLY_DESCENDING:
  node = SqlStdOperatorTable.DESC.createCall(POS, node);
 }
 if (rfc.getNullDirection()
     != dialect.defaultNullDirection(rfc.getDirection())) {
  switch (rfc.getNullDirection()) {
  case FIRST:
   node = SqlStdOperatorTable.NULLS_FIRST.createCall(POS, node);
   break;
  case LAST:
   node = SqlStdOperatorTable.NULLS_LAST.createCall(POS, node);
   break;
  }
 }
 return node;
}