MDEV-8010 - Avoid sql_alloc() in Items (Patch #1)

Added mandatory thd parameter to Item (and all derivative classes) constructor.
Added thd parameter to all routines that may create items.
Also removed "current_thd" from Item::Item. This reduced number of
pthread_getspecific() calls from 290 to 177 per OLTP RO transaction.

1 files changed, 7 insertions, 6 deletions

diff --git a/sql/item_xmlfunc.h b/sql/item_xmlfunc.h
index 5b699869b2e..3758025fc90 100644
--- a/sql/item_xmlfunc.h
+++ b/sql/item_xmlfunc.h
@@ -76,13 +76,12 @@ protected:
     return xml_arg->parse(args[0], cache);
   }
 public:
-  Item_xml_str_func(Item *a, Item *b): 
-    Item_str_func(a,b) 
+  Item_xml_str_func(THD *thd, Item *a, Item *b): Item_str_func(thd, a, b)
   {
     maybe_null= TRUE;
   }
-  Item_xml_str_func(Item *a, Item *b, Item *c): 
-    Item_str_func(a,b,c) 
+  Item_xml_str_func(THD *thd, Item *a, Item *b, Item *c):
+    Item_str_func(thd, a, b, c)
   {
     maybe_null= TRUE;
   }
@@ -102,7 +101,8 @@ public:
 class Item_func_xml_extractvalue: public Item_xml_str_func
 {
 public:
-  Item_func_xml_extractvalue(Item *a,Item *b) :Item_xml_str_func(a,b) {}
+  Item_func_xml_extractvalue(THD *thd, Item *a, Item *b):
+    Item_xml_str_func(thd, a, b) {}
   const char *func_name() const { return "extractvalue"; }
   String *val_str(String *);
 };
@@ -115,7 +115,8 @@ class Item_func_xml_update: public Item_xml_str_func
                       const MY_XML_NODE *cut,
                       const String *replace);
 public:
-  Item_func_xml_update(Item *a,Item *b,Item *c) :Item_xml_str_func(a,b,c) {}
+  Item_func_xml_update(THD *thd, Item *a, Item *b, Item *c):
+    Item_xml_str_func(thd, a, b, c) {}
   const char *func_name() const { return "updatexml"; }
   String *val_str(String *);
 };