[CALCITE-6726] Add translation for MOD operator in MSSQL

MOD is not supported in MSSQL. Translate it to %.

core/src/main/java/org/apache/calcite/sql/dialect/MssqlSqlDialect.java

@@ -33,6 +33,8 @@
 import org.apache.calcite.sql.SqlLiteral;
 import org.apache.calcite.sql.SqlNode;
 import org.apache.calcite.sql.SqlNodeList;
+import org.apache.calcite.sql.SqlOperator;
+import org.apache.calcite.sql.SqlSyntax;
 import org.apache.calcite.sql.SqlUtil;
 import org.apache.calcite.sql.SqlWriter;
 import org.apache.calcite.sql.fun.SqlStdOperatorTable;
@@ -177,7 +179,10 @@ public MssqlSqlDialect(Context context) {
         }
         unparseFloor(writer, call);
         break;
-
+      case MOD:
+        SqlOperator op = SqlStdOperatorTable.PERCENT_REMAINDER;
+        SqlSyntax.BINARY.unparse(writer, op, call, leftPrec, rightPrec);
+        break;
       default:
         super.unparseCall(writer, call, leftPrec, rightPrec);
       }

core/src/test/java/org/apache/calcite/rel/rel2sql/RelToSqlConverterTest.java

@@ -8940,6 +8940,17 @@ private void checkLiteral2(String expression, String expected) {
         .dialect(MssqlSqlDialect.DEFAULT).ok(mssqlExpected);
   }
 
+ /** Test case for
+   * <a href="https://issues.apache.org/jira/browse/CALCITE-6726">[CALCITE-6726]
+   * Add translation for MOD operator in MSSQL</a>.
+   */
+  @Test public void testModFunctionEmulationForMSSQL() {
+    final String query = "select mod(11,3)";
+    final String mssqlExpected = "SELECT 11 % 3\nFROM (VALUES (0)) AS [t] ([ZERO])";
+    sql(query).dialect(MssqlSqlDialect.DEFAULT).ok(mssqlExpected);
+  }
+
+
   /** Test case for
    * <a href="https://issues.apache.org/jira/browse/CALCITE-6655">[CALCITE-6655]
    * Aggregation of deeply nested window not detected when unparsing</a>.