type_blob.result, func_system.result, func_str.result, ctype_collate.result:

  fixing test results accordingly.
func_system.test:
  New test that illegal mix of collations does not happen anymore.
item_strfunc.h:
    safe_charset_converter() was added for system constants.
item_strfunc.cc:
  safe_charset_converter() was added for system constants.
item_func.cc, item.h, item.cc:
  Bug#8291: Illegal collation mix with USER() function.
  After discussion with PeterG and Serge, a new coercibility
  level for "system constants" was introduced, between
  COERRIBLE and IMPLICIT. Thus:
  SELECT col1 = USER() FROM t1; - is done according to col1 collation.
  SELECT 'string' = USER(); - is done according to USER() collation.
  At the same time, "nagg" and "strong" members were removed as unused.
item_create.cc:
  Version is a system constant too.

1 files changed, 12 insertions, 4 deletions

diff --git a/sql/item_strfunc.h b/sql/item_strfunc.h
index c1c0969672c..0c3ed32fb68 100644
--- a/sql/item_strfunc.h
+++ b/sql/item_strfunc.h
@@ -337,10 +337,18 @@ public:
 };
 
 
-class Item_func_database :public Item_str_func
+class Item_func_sysconst :public Item_str_func
 {
 public:
-  Item_func_database() { collation.set(system_charset_info,DERIVATION_IMPLICIT); }
+  Item_func_sysconst()
+  { collation.set(system_charset_info,DERIVATION_SYSCONST); }
+  Item *safe_charset_converter(CHARSET_INFO *tocs);
+};
+
+class Item_func_database :public Item_func_sysconst
+{
+public:
+  Item_func_database() :Item_func_sysconst() {}
   String *val_str(String *);
   void fix_length_and_dec()
   {
@@ -350,10 +358,10 @@ public:
   const char *func_name() const { return "database"; }
 };
 
-class Item_func_user :public Item_str_func
+class Item_func_user :public Item_func_sysconst
 {
 public:
-  Item_func_user() { collation.set(system_charset_info, DERIVATION_IMPLICIT); }
+  Item_func_user() :Item_func_sysconst() {}
   String *val_str(String *);
   void fix_length_and_dec() 
   {