Fixed bug #34620: item_row.cc:50: Item_row::illegal_method_call(const char*):

                  Assertion `0' failed

If ROW item is a part of an expression that also has
aggregate function calls (COUNT/SUM/AVG...), a
"splitting" with an Item::split_sum_func2 function
is applied to that ROW item.
Current implementation of Item::split_sum_func2
replaces this Item_row with a newly created
Item_aggregate_ref reference to it.
Then the row cache tries to work with the
Item_aggregate_ref object as with the Item_row object:
row cache calls row-emulation methods such as cols and
element_index. Item_aggregate_ref (like it's parent
Item_ref) inherits dummy implementations of those
methods from the hierarchy root Item, and call to
them leads to failed assertions and wrong data
output.

Row-emulation virtual functions (cols, element_index, addr,
check_cols, null_inside and bring_value) of Item_ref have
been overloaded to forward calls to an underlying item
reference.

mysql-test/r/row.result

@@ -434,3 +434,12 @@ SELECT @x;
 @x
 99
 DROP TABLE t1;
+CREATE TABLE t1 (a INT, b INT);
+INSERT INTO t1 VALUES (1,1);
+SELECT ROW(a, 1) IN (SELECT SUM(b), 1) FROM t1 GROUP BY a;
+ROW(a, 1) IN (SELECT SUM(b), 1)
+1
+SELECT ROW(a, 1) IN (SELECT SUM(b), 3) FROM t1 GROUP BY a;
+ROW(a, 1) IN (SELECT SUM(b), 3)
+0
+DROP TABLE t1;

mysql-test/t/row.test

@@ -224,3 +224,16 @@ SET @x:= (SELECT h FROM t1 WHERE (a,b,c,d,e,f,g)=(1,2,3,4,5,6,7));
 SELECT @x;
 
 DROP TABLE t1;
+
+#
+# Bug #34620: item_row.cc:50: Item_row::illegal_method_call(const char*):
+#             Assertion `0' failed
+#
+
+CREATE TABLE t1 (a INT, b INT);
+INSERT INTO t1 VALUES (1,1);
+
+SELECT ROW(a, 1) IN (SELECT SUM(b), 1) FROM t1 GROUP BY a;
+SELECT ROW(a, 1) IN (SELECT SUM(b), 3) FROM t1 GROUP BY a;
+
+DROP TABLE t1;

sql/item.h

@@ -1990,6 +1990,35 @@ public:
   Item_field *filed_for_view_update()
     { return (*ref)->filed_for_view_update(); }
   virtual Ref_Type ref_type() { return REF; }
+
+  // Row emulation: forwarding of ROW-related calls to ref
+  uint cols()
+  {
+    return ref && result_type() == ROW_RESULT ? (*ref)->cols() : 1;
+  }
+  Item* element_index(uint i)
+  {
+    return ref && result_type() == ROW_RESULT ? (*ref)->element_index(i) : this;
+  }
+  Item** addr(uint i)
+  {
+    return ref && result_type() == ROW_RESULT ? (*ref)->addr(i) : 0;
+  }
+  bool check_cols(uint c)
+  {
+    return ref && result_type() == ROW_RESULT ? (*ref)->check_cols(c) 
+                                              : Item::check_cols(c);
+  }
+  bool null_inside()
+  {
+    return ref && result_type() == ROW_RESULT ? (*ref)->null_inside() : 0;
+  }
+  void bring_value()
+  { 
+    if (ref && result_type() == ROW_RESULT)
+      (*ref)->bring_value();
+  }
+
 };