MDEV-17137: Syntax errors with VIEW using MEDIAN

The syntax error happened because we had not implemented a different print for
percentile functions. The syntax is a bit different when we use percentile functions
as window functions in comparision to normal window functions.
Implemented a seperate print function for percentile functions

mysql-test/main/win_percentile.result

@@ -348,3 +348,21 @@ MEDIAN(`a2`) OVER (PARTITION BY `pk`)
 FROM t1;
 MEDIAN(`a1`) OVER ()	MEDIAN(`a2`) OVER (PARTITION BY `pk`)
 DROP TABLE t1;
+#
+# MDEV-17137: Syntax errors with VIEW using MEDIAN
+#
+CREATE TABLE t1(val int);
+INSERT INTO t1 VALUES (1), (2), (3);
+CREATE VIEW v1 AS SELECT MEDIAN(val) OVER() FROM t1;
+select * from v1;
+MEDIAN(val) OVER()
+2.0000000000
+2.0000000000
+2.0000000000
+select median(val) OVER () FROM t1;
+median(val) OVER ()
+2.0000000000
+2.0000000000
+2.0000000000
+drop table t1;
+drop view v1;

mysql-test/main/win_percentile.test

@@ -127,3 +127,15 @@ SELECT MEDIAN(`a1`) OVER (),
        MEDIAN(`a2`) OVER (PARTITION BY `pk`)
 FROM t1;
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-17137: Syntax errors with VIEW using MEDIAN
+--echo #
+
+CREATE TABLE t1(val int);
+INSERT INTO t1 VALUES (1), (2), (3);
+CREATE VIEW v1 AS SELECT MEDIAN(val) OVER() FROM t1;
+select * from v1;
+select median(val) OVER () FROM t1;
+drop table t1;
+drop view v1;

sql/item_windowfunc.cc

@@ -545,6 +545,11 @@ void Item_sum_hybrid_simple::update_field()
 
 void Item_window_func::print(String *str, enum_query_type query_type)
 {
+  if (only_single_element_order_list())
+  {
+    print_for_percentile_functions(str, query_type);
+    return;
+  }
   window_func()->print(str, query_type);
   str->append(" over ");
 #ifndef DBUG_OFF
@@ -554,3 +559,15 @@ void Item_window_func::print(String *str, enum_query_type query_type)
 #endif
   window_spec->print(str, query_type);
 }
+void Item_window_func::print_for_percentile_functions(String *str, enum_query_type query_type)
+{
+  window_func()->print(str, query_type);
+  str->append(" within group ");
+  str->append('(');
+  window_spec->print_order(str,query_type);
+  str->append(')');
+  str->append(" over ");
+  str->append('(');
+  window_spec->print_partition(str,query_type);
+  str->append(')');
+}

sql/item_windowfunc.h

@@ -1155,6 +1155,7 @@ private:
   */
   bool force_return_blank;
   bool read_value_from_result_field;
+  void print_for_percentile_functions(String *str, enum_query_type query_type);
 
 public:
   void set_phase_to_initial()

sql/sql_window.cc

@@ -82,19 +82,32 @@ void
 Window_spec::print(String *str, enum_query_type query_type)
 {
   str->append('(');
+  print_partition(str, query_type);
+  print_order(str, query_type);
+
+  if (window_frame)
+    window_frame->print(str, query_type);
+  str->append(')');
+}
+
+void
+Window_spec::print_partition(String *str, enum_query_type query_type)
+{
   if (partition_list->first)
   {
     str->append(STRING_WITH_LEN(" partition by "));
     st_select_lex::print_order(str, partition_list->first, query_type);
   }
+}
+
+void
+Window_spec::print_order(String *str, enum_query_type query_type)
+{
   if (order_list->first)
   {
     str->append(STRING_WITH_LEN(" order by "));
     st_select_lex::print_order(str, order_list->first, query_type);
   }
-  if (window_frame)
-    window_frame->print(str, query_type);
-  str->append(')');
 }
 
 bool

sql/sql_window.h

@@ -147,6 +147,8 @@ class Window_spec : public Sql_alloc
   }
 
   void print(String *str, enum_query_type query_type);
+  void print_order(String *str, enum_query_type query_type);
+  void print_partition(String *str, enum_query_type query_type);
 
 };