Bug#20095 Changing length of VARCHAR field with UTF8 collation does not truncate values

Problem: single byte do_varstring1() function was called, which didn't
check limit on "number of character", and checked only "number of bytes".
Fix: adding a multi-byte aware function do_varstring1_mb(),
to limit on "number of characters"


mysql-test/r/ctype_utf8.result:
  Adding test case
mysql-test/t/ctype_utf8.test:
  Adding test case
sql/field_conv.cc:
  Adding missing function to copy VARCHAR strings
  having one length byte.

1 files changed, 30 insertions, 2 deletions

diff --git a/sql/field_conv.cc b/sql/field_conv.cc
index 429d914db97..5670b1e0676 100644
--- a/sql/field_conv.cc
+++ b/sql/field_conv.cc
@@ -434,6 +434,26 @@ static void do_varstring1(Copy_field *copy)
 }
 
 
+static void do_varstring1_mb(Copy_field *copy)
+{
+  int well_formed_error;
+  CHARSET_INFO *cs= copy->from_field->charset();
+  uint from_length= (uint) *(uchar*) copy->from_ptr;
+  const char *from_ptr= copy->from_ptr + 1;
+  uint to_char_length= (copy->to_length - 1) / cs->mbmaxlen;
+  uint length= cs->cset->well_formed_len(cs, from_ptr, from_ptr + from_length,
+                                         to_char_length, &well_formed_error);
+  if (length < from_length)
+  {
+    if (current_thd->count_cuted_fields)
+      copy->to_field->set_warning(MYSQL_ERROR::WARN_LEVEL_WARN,
+                                  WARN_DATA_TRUNCATED, 1);
+  }
+  *(uchar*) copy->to_ptr= (uchar) length;
+  memcpy(copy->to_ptr + 1, from_ptr, length);
+}
+
+
 static void do_varstring2(Copy_field *copy)
 {
   uint length=uint2korr(copy->from_ptr);
@@ -459,6 +479,12 @@ static void do_varstring2_mb(Copy_field *copy)
   const char *from_beg= copy->from_ptr + HA_KEY_BLOB_LENGTH;
   uint length= cs->cset->well_formed_len(cs, from_beg, from_beg + from_length,
                                          char_length, &well_formed_error);
+  if (length < from_length)
+  {
+    if (current_thd->count_cuted_fields)
+      copy->to_field->set_warning(MYSQL_ERROR::WARN_LEVEL_WARN,
+                                  WARN_DATA_TRUNCATED, 1);
+  }  
   int2store(copy->to_ptr, length);
   memcpy(copy->to_ptr+HA_KEY_BLOB_LENGTH, from_beg, length);
 }
@@ -634,8 +660,10 @@ void (*Copy_field::get_copy_func(Field *to,Field *from))(Copy_field*)
           return do_field_string;
         if (to_length != from_length)
           return (((Field_varstring*) to)->length_bytes == 1 ?
-                  do_varstring1 : (from->charset()->mbmaxlen == 1 ?
-                                   do_varstring2 : do_varstring2_mb));
+                  (from->charset()->mbmaxlen == 1 ? do_varstring1 :
+                                                    do_varstring1_mb) :
+                  (from->charset()->mbmaxlen == 1 ? do_varstring2 :
+                                                    do_varstring2_mb));
       }
       else if (to_length < from_length)
 	return (from->charset()->mbmaxlen == 1 ?