MDEV-20674 Reuse val_native() in ExtractValue() and UpdateXML()

sql/item.h

@@ -1467,7 +1467,6 @@ class Item: public Value_source,
   {
     return type_handler()->Item_val_bool(this);
   }
-  virtual String *val_raw(String*) { return 0; }
 
   bool eval_const_cond()
   {

sql/item_xmlfunc.h

@@ -2,6 +2,7 @@
 #define ITEM_XMLFUNC_INCLUDED
 
 /* Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2009, 2019, MariaDB
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -23,6 +24,42 @@
 typedef struct my_xml_node_st MY_XML_NODE;
 
 
+/* Structure to store nodeset elements */
+class MY_XPATH_FLT
+{
+public:
+  uint num;     // Absolute position in MY_XML_NODE array
+  uint pos;     // Relative position in context
+  uint size;    // Context size
+public:
+  MY_XPATH_FLT(uint32 num_arg, uint32 pos_arg)
+   :num(num_arg), pos(pos_arg), size(0)
+  { }
+  MY_XPATH_FLT(uint32 num_arg, uint32 pos_arg, uint32 size_arg)
+   :num(num_arg), pos(pos_arg), size(size_arg)
+  { }
+  bool append_to(Native *to) const
+  {
+    return to->append((const char*) this, (uint32) sizeof(*this));
+  }
+};
+
+
+class NativeNodesetBuffer: public NativeBuffer<16*sizeof(MY_XPATH_FLT)>
+{
+public:
+  const MY_XPATH_FLT &element(uint i) const
+  {
+    const MY_XPATH_FLT *p= (MY_XPATH_FLT*) (ptr() + i * sizeof(MY_XPATH_FLT));
+    return *p;
+  }
+  uint32 elements() const
+  {
+    return length() / sizeof(MY_XPATH_FLT);
+  }
+};
+
+
 class Item_xml_str_func: public Item_str_func
 {
 protected:
@@ -103,7 +140,8 @@ class Item_func_xml_extractvalue: public Item_xml_str_func
 
 class Item_func_xml_update: public Item_xml_str_func
 {
-  String tmp_value2, tmp_value3;
+  NativeNodesetBuffer tmp_native_value2;
+  String tmp_value3;
   bool collect_result(String *str,
                       const MY_XML_NODE *cut,
                       const String *replace);