[GitHub] [calcite] jinxing64 commented on a change in pull request #1285: [CALCITE-3154] RelToSqlConverter generated Nulls Last and Nulls First when convert RexOver to sql using MysqlSqlDialect.

[GitBox <gi...@apache.org>]

jinxing64 commented on a change in pull request #1285: [CALCITE-3154] RelToSqlConverter generated Nulls Last and Nulls First when convert RexOver to sql using MysqlSqlDialect.
URL: https://github.com/apache/calcite/pull/1285#discussion_r300592380
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/rel/rel2sql/SqlImplementor.java
 ##########
 @@ -795,6 +795,29 @@ void addOrderItem(List<SqlNode> orderByList, RelFieldCollation field) {
       orderByList.add(toSql(field));
     }
 
+
+    void addOrderItem(List<SqlNode> orderByList, RexProgram program, RexFieldCollation field) {
+      SqlNode node = toSql(program, field.left);
+      SqlNode nullDirectionNode = null;
+      if (field.getNullDirection() != RelFieldCollation.NullDirection.UNSPECIFIED) {
+        final boolean first =
+                  field.getNullDirection() == RelFieldCollation.NullDirection.FIRST;
+        nullDirectionNode = dialect.emulateNullDirection(
+                node, first, field.getDirection().isDescending());
+      }
+      if (nullDirectionNode != null) {
+        orderByList.add(nullDirectionNode);
+        switch (field.getDirection()) {
+        case DESCENDING:
+        case STRICTLY_DESCENDING:
+          node = SqlStdOperatorTable.DESC.createCall(POS, node);
 
 Review comment:
   From code style, I'd prefer a  `default` case here and doc 'do-nothing'

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