Allow IN to convert arguments into Unicode in some cases.

1 files changed, 50 insertions, 4 deletions

diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index f91bc5c4bc5..4ddb648399a 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -1735,12 +1735,58 @@ void Item_func_in::fix_length_and_dec()
   uint const_itm= 1;
   
   agg_cmp_type(&cmp_type, args, arg_count);
-  if ((cmp_type == STRING_RESULT) &&
-      (agg_arg_collations_for_comparison(cmp_collation, args, arg_count)))
-    return;
-  
+
   for (arg=args+1, arg_end=args+arg_count; arg != arg_end ; arg++)
     const_itm&= arg[0]->const_item();
+
+
+  if (cmp_type == STRING_RESULT)
+  {
+    /*
+      We allow consts character set conversion for
+
+        item IN (const1, const2, const3, ...)
+
+      if item is in a superset for all arguments,
+      and if it is a stong side according to coercibility rules.
+   
+      TODO: add covnersion for non-constant IN values
+      via creating Item_func_conv_charset().
+    */
+
+    if (agg_arg_collations_for_comparison(cmp_collation,
+                                          args, arg_count, TRUE))
+      return;
+    if ((!my_charset_same(args[0]->collation.collation, 
+                          cmp_collation.collation) || !const_itm))
+    {
+      if (agg_arg_collations_for_comparison(cmp_collation,
+                                            args, arg_count, FALSE))
+        return;
+    }
+    else
+    {
+      /* 
+         Conversion is possible:
+         All IN arguments are constants.
+      */
+      for (arg= args+1, arg_end= args+arg_count; arg < arg_end; arg++)
+      {
+        if (!my_charset_same(cmp_collation.collation,
+                             arg[0]->collation.collation))
+        {
+          Item_string *conv;
+          String tmp, cstr, *ostr= arg[0]->val_str(&tmp);
+          cstr.copy(ostr->ptr(), ostr->length(), ostr->charset(),
+                    cmp_collation.collation);
+          conv= new Item_string(cstr.ptr(),cstr.length(), cstr.charset(),
+                                arg[0]->collation.derivation);
+          conv->str_value.copy();
+          arg[0]= conv;
+        }
+      }
+    }
+  }
   
   /*
     Row item with NULLs inside can return NULL or FALSE =>