Many files:

  Allow mixing of different character sets for more SQL functions.
item_func.h:
  Allow mixing of different character sets for more SQL functions..


sql/item_cmpfunc.cc:
  Allow mixing of different character sets for more SQL functions.
sql/item_func.cc:
  Allow mixing of different character sets for more SQL functions.
sql/item_func.h:
  Allow mixing of different character sets for more SQL functions..
sql/item_strfunc.cc:
  Allow mixing of different character sets for more SQL functions.
sql/item.cc:
  Allow mixing of different character sets for more SQL functions.
sql/item.h:
  Allow mixing of different character sets for more SQL functions.
mysql-test/t/ctype_recoding.test:
  Allow mixing of different character sets for more SQL functions.
mysql-test/r/ctype_recoding.result:
  Allow mixing of different character sets for more SQL functions.

mysql-test/r/ctype_recoding.result

@@ -186,3 +186,57 @@ select * from t1 where a=_latin1'
 ERROR HY000: Illegal mix of collations (cp1251_general_ci,IMPLICIT) and (latin1_swedish_ci,COERCIBLE) for operation '='
 drop table t1;
 set names latin1;
+set names koi8r;
+create table t1 (c1 char(10) character set cp1251);
+insert into t1 values ('');
+select c1 from t1 where c1 between '' and '';
+c1
+
+select ifnull(c1,''), ifnull(null,c1) from t1;
+ifnull(c1,'')	ifnull(null,c1)
+	
+select if(1,c1,''), if(0,c1,'') from t1;
+if(1,c1,'')	if(0,c1,'')
+	
+select coalesce('',c1), coalesce(null,c1) from t1;
+coalesce('',c1)	coalesce(null,c1)
+	
+select least(c1,''), greatest(c1,'') from t1;
+least(c1,'')	greatest(c1,'')
+	
+select locate(c1,''), locate('',c1) from t1;
+locate(c1,'')	locate('',c1)
+1	1
+select field(c1,''),field('',c1) from t1;
+field(c1,'')	field('',c1)
+1	1
+select concat(c1,''), concat('',c1) from t1;
+concat(c1,'')	concat('',c1)
+	
+select concat_ws(c1,'',''), concat_ws('',c1,'') from t1;
+concat_ws(c1,'','')	concat_ws('',c1,'')
+	
+select replace(c1,'',''), replace('',c1,'') from t1;
+replace(c1,'','')	replace('',c1,'')
+	
+select substring_index(c1,'',2) from t1;
+substring_index(c1,'',2)
+
+select elt(1,c1,''),elt(1,'',c1) from t1;
+elt(1,c1,'')	elt(1,'',c1)
+	
+select make_set(3,c1,''), make_set(3,'',c1) from t1;
+make_set(3,c1,'')	make_set(3,'',c1)
+,	,
+select insert(c1,1,2,''),insert('',1,2,c1) from t1;
+insert(c1,1,2,'')	insert('',1,2,c1)
+	
+select trim(c1 from ''),trim('' from c1) from t1;
+trim(c1 from '')	trim('' from c1)
+	
+select lpad(c1,3,''), lpad('',3,c1) from t1;
+lpad(c1,3,'')	lpad('',3,c1)
+	
+select rpad(c1,3,''), rpad('',3,c1) from t1;
+rpad(c1,3,'')	rpad('',3,c1)
+	

mysql-test/t/ctype_recoding.test

@@ -153,3 +153,29 @@ select * from t1 where a=_latin1'
 drop table t1;
 set names latin1;
 
+#
+# Check more automatic conversion
+#
+set names koi8r;
+create table t1 (c1 char(10) character set cp1251);
+insert into t1 values ('');
+select c1 from t1 where c1 between '' and '';
+select ifnull(c1,''), ifnull(null,c1) from t1;
+select if(1,c1,''), if(0,c1,'') from t1;
+select coalesce('',c1), coalesce(null,c1) from t1;
+select least(c1,''), greatest(c1,'') from t1;
+select locate(c1,''), locate('',c1) from t1;
+select field(c1,''),field('',c1) from t1;
+select concat(c1,''), concat('',c1) from t1;
+select concat_ws(c1,'',''), concat_ws('',c1,'') from t1;
+select replace(c1,'',''), replace('',c1,'') from t1;
+select substring_index(c1,'',2) from t1;
+select elt(1,c1,''),elt(1,'',c1) from t1;
+select make_set(3,c1,''), make_set(3,'',c1) from t1;
+select insert(c1,1,2,''),insert('',1,2,c1) from t1;
+select trim(c1 from ''),trim('' from c1) from t1;
+select lpad(c1,3,''), lpad('',3,c1) from t1;
+select rpad(c1,3,''), rpad('',3,c1) from t1;
+# TODO
+#select case c1 when '' then '' when '' then '' else 'c' end from t1;
+#select export_set(5,c1,''), export_set(5,'',c1) from t1;

sql/item.cc

@@ -205,6 +205,41 @@ bool Item::eq(const Item *item, bool binary_cmp) const
 }
 
 
+Item *Item::safe_charset_converter(CHARSET_INFO *tocs)
+{
+  /*
+    Don't allow automatic conversion to non-Unicode charsets,
+    as it potentially loses data.
+  */
+  if (!(tocs->state & MY_CS_UNICODE))
+    return NULL; // safe conversion is not possible
+  return new Item_func_conv_charset(this, tocs);
+}
+
+
+Item *Item_string::safe_charset_converter(CHARSET_INFO *tocs)
+{
+  Item_string *conv;
+  uint conv_errors;
+  String tmp, cstr, *ostr= val_str(&tmp);
+  cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(), tocs, &conv_errors);
+  if (conv_errors || !(conv= new Item_string(cstr.ptr(), cstr.length(),
+                                             cstr.charset(),
+                                             collation.derivation)))
+  {
+    /*
+      Safe conversion is not possible (or EOM).
+      We could not convert a string into the requested character set
+      without data loss. The target charset does not cover all the
+      characters from the string. Operation cannot be done correctly.
+    */
+    return NULL;
+  }
+  conv->str_value.copy();
+  return conv;
+}
+
+
 bool Item_string::eq(const Item *item, bool binary_cmp) const
 {
   if (type() == item->type())
@@ -723,6 +758,12 @@ String *Item_null::val_str(String *str)
 }
 
 
+Item *Item_null::safe_charset_converter(CHARSET_INFO *tocs)
+{
+  collation.set(tocs);
+  return this;
+}
+
 /*********************** Item_param related ******************************/
 
 /* 

sql/item.h

@@ -39,13 +39,22 @@ enum Derivation
 
 /*
   Flags for collation aggregation modes:
-  allow conversion to a superset
-  allow conversion of a coercible value (i.e. constant).
+  MY_COLL_ALLOW_SUPERSET_CONV  - allow conversion to a superset
+  MY_COLL_ALLOW_COERCIBLE_CONV - allow conversion of a coercible value
+                                 (i.e. constant).
+  MY_COLL_ALLOW_CONV           - allow any kind of conversion
+                                 (combintion of the above two)
+  MY_COLL_DISALLOW_NONE        - don't allow return DERIVATION_NONE
+                                 (e.g. when aggregating for comparison)
+  MY_COLL_CMP_CONV             - combination of MY_COLL_ALLOW_CONV
+                                 and MY_COLL_DISALLOW_NONE
 */
 
 #define MY_COLL_ALLOW_SUPERSET_CONV   1
 #define MY_COLL_ALLOW_COERCIBLE_CONV  2
-
+#define MY_COLL_ALLOW_CONV            3
+#define MY_COLL_DISALLOW_NONE         4
+#define MY_COLL_CMP_CONV              7
 
 class DTCollation {
 public:
@@ -302,6 +311,7 @@ class Item {
   Field *tmp_table_field_from_field_type(TABLE *table);
 
   virtual Item *neg_transformer(THD *thd) { return NULL; }
+  virtual Item *safe_charset_converter(CHARSET_INFO *tocs);
   void delete_self()
   {
     cleanup();
@@ -447,6 +457,7 @@ class Item_null :public Item
   Item *new_item() { return new Item_null(name); }
   bool is_null() { return 1; }
   void print(String *str) { str->append("NULL", 4); }
+  Item *safe_charset_converter(CHARSET_INFO *tocs);
 };
 
 
@@ -717,6 +728,7 @@ class Item_string :public Item
     return new Item_string(name, str_value.ptr(), 
     			   str_value.length(), &my_charset_bin);
   }
+  Item *safe_charset_converter(CHARSET_INFO *tocs);
   String *const_string() { return &str_value; }
   inline void append(char *str, uint length) { str_value.append(str, length); }
   void print(String *str);

sql/item_cmpfunc.cc

@@ -173,89 +173,11 @@ void Item_bool_func2::fix_length_and_dec()
   if (!args[0] || !args[1])
     return;
 
-  /* 
-    We allow to apply automatic character set conversion in some cases.
-    The conditions when conversion is possible are:
-    - arguments A and B have different charsets
-    - A wins according to coercibility rules
-      (i.e. a column is stronger than a string constant,
-       an explicit COLLATE clause is stronger than a column)
-    - character set of A is either superset for character set of B,
-      or B is a string constant which can be converted into the
-      character set of A without data loss.
-    
-    If all of the above is true, then it's possible to convert
-    B into the character set of A, and then compare according
-    to the collation of A.
-  */
-
-  uint32 dummy_offset;
   DTCollation coll;
-
   if (args[0]->result_type() == STRING_RESULT &&
       args[1]->result_type() == STRING_RESULT &&
-      String::needs_conversion(0, args[0]->collation.collation,
-                                  args[1]->collation.collation,
-                                  &dummy_offset) &&
-      !coll.set(args[0]->collation, args[1]->collation,
-                MY_COLL_ALLOW_SUPERSET_CONV | 
-                MY_COLL_ALLOW_COERCIBLE_CONV))
-  {
-    Item* conv= 0;
-    Item_arena *arena= thd->current_arena, backup;
-    uint strong= coll.strong;
-    uint weak= strong ? 0 : 1;
-    /*
-      In case we're in statement prepare, create conversion item
-      in its memory: it will be reused on each execute.
-    */
-    if (arena->is_stmt_prepare())
-        thd->set_n_backup_item_arena(arena, &backup);
-    if (args[weak]->type() == STRING_ITEM)
-    {
-      uint conv_errors; 
-      String tmp, cstr, *ostr= args[weak]->val_str(&tmp);
-      cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(), 
-                args[strong]->collation.collation, &conv_errors);
-      if (conv_errors)
-      {
-        /* 
-          We could not convert a string into the character set
-          of the stronger side of the operation without data loss.
-          It can happen if we tried to combine a column with a string
-          constant, and the column charset does not cover all the
-          characters from the string. Operation cannot be done
-          correctly. Return an error.
-        */
-        my_coll_agg_error(args[0]->collation, args[1]->collation,
-                          func_name());
-        return;
-      }
-      conv= new Item_string(cstr.ptr(),cstr.length(),cstr.charset(),
-                            args[weak]->collation.derivation);
-      ((Item_string*)conv)->str_value.copy();
-    }
-    else
-    {
-      if (!(coll.collation->state & MY_CS_UNICODE))
-      {
-        /*
-          Don't allow automatic conversion to non-Unicode charsets,
-          as it potentially loses data.
-        */
-        my_coll_agg_error(args[0]->collation, args[1]->collation,
-                          func_name());
-        return;
-      }
-      conv= new Item_func_conv_charset(args[weak],
-                                       args[strong]->collation.collation);
-      conv->collation.set(args[weak]->collation.derivation);
-      conv->fix_fields(thd, 0, &conv);
-    }
-    if (arena->is_stmt_prepare())
-      thd->restore_backup_item_arena(arena, &backup);
-    args[weak]= conv ? conv : args[weak];
-  }
+      agg_arg_charsets(coll, args, 2, MY_COLL_CMP_CONV))
+    return;
   
   // Make a special case of compare with fields to get nicer DATE comparisons
 
@@ -871,7 +793,7 @@ void Item_func_between::fix_length_and_dec()
     return;
   agg_cmp_type(&cmp_type, args, 3);
   if (cmp_type == STRING_RESULT &&
-      agg_arg_collations_for_comparison(cmp_collation, args, 3))
+      agg_arg_charsets(cmp_collation, args, 3, MY_COLL_CMP_CONV))
     return;
 
   /*
@@ -987,7 +909,7 @@ Item_func_ifnull::fix_length_and_dec()
   decimals=max(args[0]->decimals,args[1]->decimals);
   agg_result_type(&cached_result_type, args, 2);
   if (cached_result_type == STRING_RESULT)
-    agg_arg_collations(collation, args, arg_count);
+    agg_arg_charsets(collation, args, arg_count, MY_COLL_CMP_CONV);
   else if (cached_result_type != REAL_RESULT)
     decimals= 0;
   
@@ -1083,7 +1005,7 @@ Item_func_if::fix_length_and_dec()
     agg_result_type(&cached_result_type, args+1, 2);
     if (cached_result_type == STRING_RESULT)
     {
-      if (agg_arg_collations(collation, args+1, 2))
+      if (agg_arg_charsets(collation, args+1, 2, MY_COLL_ALLOW_CONV))
       return;
     }
     else
@@ -1354,7 +1276,7 @@ void Item_func_case::fix_length_and_dec()
   
   agg_result_type(&cached_result_type, agg, nagg);
   if ((cached_result_type == STRING_RESULT) &&
-      agg_arg_collations(collation, agg, nagg))
+      agg_arg_charsets(collation, agg, nagg, MY_COLL_ALLOW_CONV))
     return;
   
   
@@ -1370,7 +1292,7 @@ void Item_func_case::fix_length_and_dec()
     nagg++;
     agg_cmp_type(&cmp_type, agg, nagg);
     if ((cmp_type == STRING_RESULT) &&
-        agg_arg_collations_for_comparison(cmp_collation, agg, nagg))
+        agg_arg_charsets(cmp_collation, agg, nagg, MY_COLL_CMP_CONV))
     return;
   }
   
@@ -1477,7 +1399,7 @@ void Item_func_coalesce::fix_length_and_dec()
     set_if_bigger(decimals,args[i]->decimals);
   }
   if (cached_result_type == STRING_RESULT)
-    agg_arg_collations(collation, args, arg_count);
+    agg_arg_charsets(collation, args, arg_count, MY_COLL_ALLOW_CONV);
   else if (cached_result_type != REAL_RESULT)
     decimals= 0;
 }
@@ -2423,7 +2345,7 @@ Item_func_regex::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
   max_length= 1;
   decimals= 0;
 
-  if (agg_arg_collations(cmp_collation, args, 2))
+  if (agg_arg_charsets(cmp_collation, args, 2, MY_COLL_CMP_CONV))
     return 1;
 
   used_tables_cache=args[0]->used_tables() | args[1]->used_tables();

sql/item_func.cc

@@ -90,6 +90,12 @@ bool Item_func::agg_arg_collations(DTCollation &c, Item **av, uint count,
       return TRUE;
     }
   }
+  if ((flags & MY_COLL_DISALLOW_NONE) &&
+      c.derivation == DERIVATION_NONE)
+  {
+    my_coll_agg_error(av, count, func_name());
+    return TRUE;
+  }
   return FALSE;
 }
 
@@ -98,15 +104,7 @@ bool Item_func::agg_arg_collations_for_comparison(DTCollation &c,
 						  Item **av, uint count,
                                                   uint flags)
 {
-  if (agg_arg_collations(c, av, count, flags))
-    return TRUE;
-
-  if (c.derivation == DERIVATION_NONE)
-  {
-    my_coll_agg_error(av, count, func_name());
-    return TRUE;
-  }
-  return FALSE;
+  return (agg_arg_collations(c, av, count, flags | MY_COLL_DISALLOW_NONE));
 }
 
 
@@ -119,6 +117,89 @@ eval_const_cond(COND *cond)
 }
 
 
+
+/* 
+  Collect arguments' character sets together.
+  We allow to apply automatic character set conversion in some cases.
+  The conditions when conversion is possible are:
+  - arguments A and B have different charsets
+  - A wins according to coercibility rules
+    (i.e. a column is stronger than a string constant,
+     an explicit COLLATE clause is stronger than a column)
+  - character set of A is either superset for character set of B,
+    or B is a string constant which can be converted into the
+    character set of A without data loss.
+    
+  If all of the above is true, then it's possible to convert
+  B into the character set of A, and then compare according
+  to the collation of A.
+  
+  For functions with more than two arguments:
+
+    collect(A,B,C) ::= collect(collect(A,B),C)
+*/
+
+bool Item_func::agg_arg_charsets(DTCollation &coll,
+                                 Item **args, uint nargs, uint flags)
+{
+  Item **arg, **last, *safe_args[2];
+  if (agg_arg_collations(coll, args, nargs, flags))
+    return TRUE;
+
+  /*
+    For better error reporting: save the first and the second argument.
+    We need this only if the the number of args is 3 or 2:
+    - for a longer argument list, "Illegal mix of collations"
+      doesn't display each argument's characteristics.
+    - if nargs is 1, then this error cannot happen.
+  */
+  if (nargs >=2 && nargs <= 3)
+  {
+    safe_args[0]= args[0];
+    safe_args[1]= args[1];
+  }
+
+  THD *thd= current_thd;
+  Item_arena *arena= thd->current_arena, backup;
+  bool res= FALSE;
+  /*
+    In case we're in statement prepare, create conversion item
+    in its memory: it will be reused on each execute.
+  */
+  if (arena->is_stmt_prepare())
+    thd->set_n_backup_item_arena(arena, &backup);
+
+  for (arg= args, last= args + nargs; arg < last; arg++)
+  {
+    Item* conv;
+    uint dummy_offset;
+    if (!String::needs_conversion(0, coll.collation,
+                                  (*arg)->collation.collation,
+                                  &dummy_offset))
+      continue;
+
+    if (!(conv= (*arg)->safe_charset_converter(coll.collation)))
+    {
+      if (nargs >=2 && nargs <= 3)
+      {
+        /* restore the original arguments for better error message */
+        args[0]= safe_args[0];
+        args[1]= safe_args[1];
+      }
+      my_coll_agg_error(args, nargs, func_name());
+      res= TRUE;
+      break; // we cannot return here, we need to restore "arena".
+    }
+    conv->fix_fields(thd, 0, &conv);
+    *arg= conv;
+  }
+  if (arena->is_stmt_prepare())
+    thd->restore_backup_item_arena(arena, &backup);
+  return res;
+}
+
+
+
 void Item_func::set_arguments(List<Item> &list)
 {
   allowed_arg_cols= 1;
@@ -1105,7 +1186,7 @@ void Item_func_min_max::fix_length_and_dec()
     cmp_type=item_cmp_type(cmp_type,args[i]->result_type());
   }
   if (cmp_type == STRING_RESULT)
-    agg_arg_collations_for_comparison(collation, args, arg_count);
+    agg_arg_charsets(collation, args, arg_count, MY_COLL_CMP_CONV);
 }
 
 
@@ -1259,7 +1340,7 @@ longlong Item_func_coercibility::val_int()
 void Item_func_locate::fix_length_and_dec()
 {
   maybe_null=0; max_length=11;
-  agg_arg_collations_for_comparison(cmp_collation, args, 2);
+  agg_arg_charsets(cmp_collation, args, 2, MY_COLL_CMP_CONV);
 }
 
 
@@ -1358,7 +1439,7 @@ void Item_func_field::fix_length_and_dec()
   for (uint i=1; i < arg_count ; i++)
     cmp_type= item_cmp_type(cmp_type, args[i]->result_type());
   if (cmp_type == STRING_RESULT)
-    agg_arg_collations_for_comparison(cmp_collation, args, arg_count);
+    agg_arg_charsets(cmp_collation, args, arg_count, MY_COLL_CMP_CONV);
 }
 
 

sql/item_func.h

@@ -145,7 +145,8 @@ class Item_func :public Item_result_field
   bool agg_arg_collations_for_comparison(DTCollation &c,
                                          Item **items, uint nitems,
                                          uint flags= 0);
-
+  bool agg_arg_charsets(DTCollation &c, Item **items, uint nitems,
+                        uint flags= 0);
   bool walk(Item_processor processor, byte *arg);
 };
 

sql/item_strfunc.cc

@@ -346,7 +346,7 @@ void Item_func_concat::fix_length_and_dec()
 {
   max_length=0;
 
-  if (agg_arg_collations(collation, args, arg_count))
+  if (agg_arg_charsets(collation, args, arg_count, MY_COLL_ALLOW_CONV))
     return;
 
   for (uint i=0 ; i < arg_count ; i++)
@@ -640,7 +640,7 @@ void Item_func_concat_ws::fix_length_and_dec()
 {
   max_length=0;
 
-  if (agg_arg_collations(collation, args, arg_count))
+  if (agg_arg_charsets(collation, args, arg_count, MY_COLL_ALLOW_CONV))
     return;
 
   /*
@@ -848,7 +848,7 @@ void Item_func_replace::fix_length_and_dec()
     maybe_null=1;
   }
   
-  if (agg_arg_collations_for_comparison(collation, args, 3))
+  if (agg_arg_charsets(collation, args, 3, MY_COLL_CMP_CONV))
     return;
 }
 
@@ -893,11 +893,13 @@ String *Item_func_insert::val_str(String *str)
 
 void Item_func_insert::fix_length_and_dec()
 {
-  if (collation.set(args[0]->collation, args[3]->collation))
-  {
-      my_coll_agg_error(args[0]->collation, args[3]->collation, func_name());
-      return;
-  }
+  Item *cargs[2];
+  cargs[0]= args[0];
+  cargs[1]= args[3];
+  if (agg_arg_charsets(collation, cargs, 2, MY_COLL_ALLOW_CONV))
+    return;
+  args[0]= cargs[0];
+  args[3]= cargs[1];
   max_length=args[0]->max_length+args[3]->max_length;
   if (max_length > MAX_BLOB_WIDTH)
   {
@@ -1063,7 +1065,7 @@ void Item_func_substr_index::fix_length_and_dec()
 { 
   max_length= args[0]->max_length;
 
-  if (agg_arg_collations_for_comparison(collation, args, 2))
+  if (agg_arg_charsets(collation, args, 2, MY_COLL_CMP_CONV))
     return;
 }
 
@@ -1355,10 +1357,14 @@ void Item_func_trim::fix_length_and_dec()
     remove.set_ascii(" ",1);
   }
   else
-  if (collation.set(args[1]->collation, args[0]->collation) ||
-      collation.derivation == DERIVATION_NONE)
   {
-    my_coll_agg_error(args[1]->collation, args[0]->collation, func_name());
+    Item *cargs[2];
+    cargs[0]= args[1];
+    cargs[1]= args[0];
+    if (agg_arg_charsets(collation, cargs, 2, MY_COLL_CMP_CONV))
+      return;
+    args[0]= cargs[1];
+    args[1]= cargs[0];
   }
 }
 
@@ -1679,7 +1685,7 @@ void Item_func_elt::fix_length_and_dec()
   max_length=0;
   decimals=0;
 
-  if (agg_arg_collations(collation, args+1, arg_count-1))
+  if (agg_arg_charsets(collation, args+1, arg_count-1, MY_COLL_ALLOW_CONV))
     return;
 
   for (uint i= 1 ; i < arg_count ; i++)
@@ -1755,7 +1761,7 @@ void Item_func_make_set::fix_length_and_dec()
 {
   max_length=arg_count-1;
 
-  if (agg_arg_collations(collation, args, arg_count))
+  if (agg_arg_charsets(collation, args, arg_count, MY_COLL_ALLOW_CONV))
     return;
   
   for (uint i=0 ; i < arg_count ; i++)
@@ -1963,12 +1969,13 @@ String *Item_func_repeat::val_str(String *str)
 
 void Item_func_rpad::fix_length_and_dec()
 {
-  if (collation.set(args[0]->collation, args[2]->collation))
-  {
-    my_coll_agg_error(args[0]->collation, args[2]->collation, func_name());
+  Item *cargs[2];
+  cargs[0]= args[0];
+  cargs[1]= args[2];
+  if (agg_arg_charsets(collation, cargs, 2, MY_COLL_ALLOW_CONV))
     return;
-  }
-  
+  args[0]= cargs[0];
+  args[2]= cargs[1];
   if (args[1]->const_item())
   {
     uint32 length= (uint32) args[1]->val_int() * collation.collation->mbmaxlen;
@@ -2047,11 +2054,13 @@ String *Item_func_rpad::val_str(String *str)
 
 void Item_func_lpad::fix_length_and_dec()
 {
-  if (collation.set(args[0]->collation, args[2]->collation))
-  {
-    my_coll_agg_error(args[0]->collation, args[2]->collation, func_name());
+  Item *cargs[2];
+  cargs[0]= args[0];
+  cargs[1]= args[2];
+  if (agg_arg_charsets(collation, cargs, 2, MY_COLL_ALLOW_CONV))
     return;
-  }
+  args[0]= cargs[0];
+  args[2]= cargs[1];
   
   if (args[1]->const_item())
   {
@@ -2495,7 +2504,8 @@ void Item_func_export_set::fix_length_and_dec()
   uint sep_length=(arg_count > 3 ? args[3]->max_length : 1);
   max_length=length*64+sep_length*63;
 
-  if (agg_arg_collations(collation, args+1, min(4,arg_count)-1))
+  if (agg_arg_charsets(collation, args+1, min(4,arg_count)-1),
+                       MY_COLL_ALLOW_CONV)
     return;
 }