func_gconcat.result, func_gconcat.test:

  Adding test
item_sum.cc:
  Adding a call for collation/charset aggregation,
      to collect attributes from the arguments. The actual bug fix.
item_func.h, item_func.cc, item.h, item.cc:
  - Removing collation aggrgation functions from Item_func class
      in item.cc, and adding it as non-class functions in item.cc
      to be able to reuse this code for group_concat.
      - Adding replacement for these functions into Item_func class
      as wrappers for moved functions, to minizize patch size,

mysql-test/r/func_gconcat.result

@@ -445,6 +445,30 @@ group_concat(distinct b order by b)
 Warnings:
 Warning	1260	2 line(s) were cut by GROUP_CONCAT()
 drop table t1;
+create table t1 (a varchar(255) character set cp1250 collate cp1250_general_ci,
+b varchar(255) character set koi8r);
+insert into t1 values ('xxx','yyy');
+select collation(a) from t1;
+collation(a)
+cp1250_general_ci
+select collation(group_concat(a)) from t1;
+collation(group_concat(a))
+cp1250_general_ci
+create table t2 select group_concat(a) as a from t1;
+show create table t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `a` longtext character set cp1250
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+select collation(group_concat(a,_koi8r'test')) from t1;
+collation(group_concat(a,_koi8r'test'))
+cp1250_general_ci
+select collation(group_concat(a,_koi8r 0xC1C2)) from t1;
+ERROR HY000: Illegal mix of collations (cp1250_general_ci,IMPLICIT) and (koi8r_general_ci,COERCIBLE) for operation 'group_concat'
+select collation(group_concat(a,b)) from t1;
+ERROR HY000: Illegal mix of collations (cp1250_general_ci,IMPLICIT) and (koi8r_general_ci,IMPLICIT) for operation 'group_concat'
+drop table t1;
+drop table t2;
 CREATE TABLE t1 (id int);
 SELECT GROUP_CONCAT(id) AS gc FROM t1 HAVING gc IS NULL;
 gc

mysql-test/t/func_gconcat.test

@@ -263,6 +263,24 @@ select group_concat(distinct b order by b) from t1 group by a;
 
 drop table t1;
 
+#
+# Bug#10201
+#
+create table t1 (a varchar(255) character set cp1250 collate cp1250_general_ci,
+                 b varchar(255) character set koi8r);
+insert into t1 values ('xxx','yyy');
+select collation(a) from t1;
+select collation(group_concat(a)) from t1;
+create table t2 select group_concat(a) as a from t1;
+show create table t2;
+select collation(group_concat(a,_koi8r'test')) from t1;
+--error 1267
+select collation(group_concat(a,_koi8r 0xC1C2)) from t1;
+--error 1267
+select collation(group_concat(a,b)) from t1;
+drop table t1;
+drop table t2;
+
 #
 # bug #7769: group_concat returning null is checked in having
 #

sql/item.cc

@@ -523,6 +523,170 @@ bool DTCollation::aggregate(DTCollation &dt, uint flags)
   return 0;
 }
 
+/******************************/
+static
+void my_coll_agg_error(DTCollation &c1, DTCollation &c2, const char *fname)
+{
+  my_error(ER_CANT_AGGREGATE_2COLLATIONS,MYF(0),
+           c1.collation->name,c1.derivation_name(),
+           c2.collation->name,c2.derivation_name(),
+           fname);
+}
+
+
+static
+void my_coll_agg_error(DTCollation &c1, DTCollation &c2, DTCollation &c3,
+                       const char *fname)
+{
+  my_error(ER_CANT_AGGREGATE_3COLLATIONS,MYF(0),
+  	   c1.collation->name,c1.derivation_name(),
+	   c2.collation->name,c2.derivation_name(),
+	   c3.collation->name,c3.derivation_name(),
+	   fname);
+}
+
+
+static
+void my_coll_agg_error(Item** args, uint count, const char *fname)
+{
+  if (count == 2)
+    my_coll_agg_error(args[0]->collation, args[1]->collation, fname);
+  else if (count == 3)
+    my_coll_agg_error(args[0]->collation, args[1]->collation,
+                      args[2]->collation, fname);
+  else
+    my_error(ER_CANT_AGGREGATE_NCOLLATIONS,MYF(0),fname);
+}
+
+
+bool agg_item_collations(DTCollation &c, const char *fname,
+                         Item **av, uint count, uint flags)
+{
+  uint i;
+  c.set(av[0]->collation);
+  for (i= 1; i < count; i++)
+  {
+    if (c.aggregate(av[i]->collation, flags))
+    {
+      my_coll_agg_error(av, count, fname);
+      return TRUE;
+    }
+  }
+  if ((flags & MY_COLL_DISALLOW_NONE) &&
+      c.derivation == DERIVATION_NONE)
+  {
+    my_coll_agg_error(av, count, fname);
+    return TRUE;
+  }
+  return FALSE;
+}
+
+
+bool agg_item_collations_for_comparison(DTCollation &c, const char *fname,
+                                        Item **av, uint count, uint flags)
+{
+  return (agg_item_collations(c, fname, av, count,
+                              flags | MY_COLL_DISALLOW_NONE));
+}
+
+
+/* 
+  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 agg_item_charsets(DTCollation &coll, const char *fname,
+                       Item **args, uint nargs, uint flags)
+{
+  Item **arg, **last, *safe_args[2];
+  if (agg_item_collations(coll, fname, 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, backup;
+  bool res= FALSE;
+  /*
+    In case we're in statement prepare, create conversion item
+    in its memory: it will be reused on each execute.
+  */
+  arena= thd->change_arena_if_needed(&backup);
+
+  for (arg= args, last= args + nargs; arg < last; arg++)
+  {
+    Item* conv;
+    uint32 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, fname);
+      res= TRUE;
+      break; // we cannot return here, we need to restore "arena".
+    }
+    conv->fix_fields(thd, 0, &conv);
+    /*
+      If in statement prepare, then we create a converter for two
+      constant items, do it once and then reuse it.
+      If we're in execution of a prepared statement, arena is NULL,
+      and the conv was created in runtime memory. This can be
+      the case only if the argument is a parameter marker ('?'),
+      because for all true constants the charset converter has already
+      been created in prepare. In this case register the change for
+      rollback.
+    */
+    if (arena)
+      *arg= conv;
+    else
+      thd->change_item_tree(arg, conv);
+  }
+  if (arena)
+    thd->restore_backup_item_arena(arena, &backup);
+  return res;
+}
+
+
+
+
+/**********************************************/
+
 Item_field::Item_field(Field *f)
   :Item_ident(NullS, f->table_name, f->field_name)
 {

sql/item.h

@@ -330,6 +330,15 @@ public:
 };
 
 
+bool agg_item_collations(DTCollation &c, const char *name,
+                         Item **items, uint nitems, uint flags= 0);
+bool agg_item_collations_for_comparison(DTCollation &c, const char *name,
+                                        Item **items, uint nitems,
+                                        uint flags= 0);
+bool agg_item_charsets(DTCollation &c, const char *name,
+                       Item **items, uint nitems, uint flags= 0);
+
+
 class Item_num: public Item
 {
 public:

sql/item_func.cc

@@ -39,73 +39,6 @@ bool check_reserved_words(LEX_STRING *name)
 }
 
 
-static void my_coll_agg_error(DTCollation &c1, DTCollation &c2,
-			      const char *fname)
-{
-  my_error(ER_CANT_AGGREGATE_2COLLATIONS,MYF(0),
-	   c1.collation->name,c1.derivation_name(),
-	   c2.collation->name,c2.derivation_name(),
-	   fname);
-}
-
-static void my_coll_agg_error(DTCollation &c1,
-			       DTCollation &c2,
-			       DTCollation &c3,
-			       const char *fname)
-{
-  my_error(ER_CANT_AGGREGATE_3COLLATIONS,MYF(0),
-  	   c1.collation->name,c1.derivation_name(),
-	   c2.collation->name,c2.derivation_name(),
-	   c3.collation->name,c3.derivation_name(),
-	   fname);
-}
-
-
-static void my_coll_agg_error(Item** args, uint count, const char *fname)
-{
-  if (count == 2)
-    my_coll_agg_error(args[0]->collation, args[1]->collation, fname);
-  else if (count == 3)
-    my_coll_agg_error(args[0]->collation,
-		      args[1]->collation,
-		      args[2]->collation,
-		      fname);
-  else
-    my_error(ER_CANT_AGGREGATE_NCOLLATIONS,MYF(0),fname);
-}
-
-
-bool Item_func::agg_arg_collations(DTCollation &c, Item **av, uint count,
-                                   uint flags)
-{
-  uint i;
-  c.set(av[0]->collation);
-  for (i= 1; i < count; i++)
-  {
-    if (c.aggregate(av[i]->collation, flags))
-    {
-      my_coll_agg_error(av, count, func_name());
-      return TRUE;
-    }
-  }
-  if ((flags & MY_COLL_DISALLOW_NONE) &&
-      c.derivation == DERIVATION_NONE)
-  {
-    my_coll_agg_error(av, count, func_name());
-    return TRUE;
-  }
-  return FALSE;
-}
-
-
-bool Item_func::agg_arg_collations_for_comparison(DTCollation &c,
-						  Item **av, uint count,
-                                                  uint flags)
-{
-  return (agg_arg_collations(c, av, count, flags | MY_COLL_DISALLOW_NONE));
-}
-
-
 /* return TRUE if item is a constant */
 
 bool
@@ -115,101 +48,6 @@ 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, backup;
-  bool res= FALSE;
-  /*
-    In case we're in statement prepare, create conversion item
-    in its memory: it will be reused on each execute.
-  */
-  arena= thd->change_arena_if_needed(&backup);
-
-  for (arg= args, last= args + nargs; arg < last; arg++)
-  {
-    Item* conv;
-    uint32 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);
-    /*
-      If in statement prepare, then we create a converter for two
-      constant items, do it once and then reuse it.
-      If we're in execution of a prepared statement, arena is NULL,
-      and the conv was created in runtime memory. This can be
-      the case only if the argument is a parameter marker ('?'),
-      because for all true constants the charset converter has already
-      been created in prepare. In this case register the change for
-      rollback.
-    */
-    if (arena)
-      *arg= conv;
-    else
-      thd->change_item_tree(arg, conv);
-  }
-  if (arena)
-    thd->restore_backup_item_arena(arena, &backup);
-  return res;
-}
-
-
-
 void Item_func::set_arguments(List<Item> &list)
 {
   allowed_arg_cols= 1;

sql/item_func.h

@@ -145,12 +145,22 @@ public:
   Item *get_tmp_table_item(THD *thd);
   
   bool agg_arg_collations(DTCollation &c, Item **items, uint nitems,
-                          uint flags= 0);
+                          uint flags= 0)
+  {
+    return agg_item_collations(c, func_name(), items, nitems, flags);
+  }
   bool agg_arg_collations_for_comparison(DTCollation &c,
                                          Item **items, uint nitems,
-                                         uint flags= 0);
+                                         uint flags= 0)
+  {
+    return agg_item_collations_for_comparison(c, func_name(),
+                                              items, nitems, flags);
+  }
   bool agg_arg_charsets(DTCollation &c, Item **items, uint nitems,
-                        uint flags= 0);
+                        uint flags= 0)
+  {
+    return agg_item_charsets(c, func_name(), items, nitems, flags);
+  }
   bool walk(Item_processor processor, byte *arg);
 };
 

sql/item_sum.cc

@@ -1925,6 +1925,10 @@ Item_func_group_concat::fix_fields(THD *thd, TABLE_LIST *tables, Item **ref)
       maybe_null|= args[i]->maybe_null;
   }
 
+  if (agg_item_charsets(collation, func_name(),
+                        args, arg_count, MY_COLL_ALLOW_CONV))
+    return 1;
+
   result_field= 0;
   null_value= 1;
   max_length= group_concat_max_len;