non-functional cleanup, clarifying CONVERT_IF_BIGGER_TO_BLOB

mysql-test/r/ctype_utf16.result

@@ -1140,6 +1140,14 @@ id	l
 a	512
 Warnings:
 Warning	1260	Row 1 was cut by GROUP_CONCAT()
+SELECT id, CHAR_LENGTH(GROUP_CONCAT(body)) AS l
+FROM (SELECT 'a' AS id, REPEAT('foo bar', 100) AS body
+UNION ALL
+SELECT 'a' AS id, REPEAT('bla bla', 100) AS body) t1;
+id	l
+a	512
+Warnings:
+Warning	1260	Row 1 was cut by GROUP_CONCAT()
 #
 # End of 5.5 tests
 #

mysql-test/r/ctype_utf8.result

@@ -5055,6 +5055,14 @@ id	l
 a	1024
 Warnings:
 Warning	1260	Row 2 was cut by GROUP_CONCAT()
+SELECT id, CHAR_LENGTH(GROUP_CONCAT(body)) AS l
+FROM (SELECT 'a' AS id, REPEAT('foo bar', 100) AS body
+UNION ALL
+SELECT 'a' AS id, REPEAT('bla bla', 100) AS body) t1;
+id	l
+a	1024
+Warnings:
+Warning	1260	Row 2 was cut by GROUP_CONCAT()
 #
 # End of 5.5 tests
 #

mysql-test/t/ctype_utf16.test

@@ -777,6 +777,10 @@ SELECT 'a' AS id, REPEAT('bla bla', 100) AS body) t1
 GROUP BY id
 ORDER BY l DESC;
 
+SELECT id, CHAR_LENGTH(GROUP_CONCAT(body)) AS l
+FROM (SELECT 'a' AS id, REPEAT('foo bar', 100) AS body
+UNION ALL
+SELECT 'a' AS id, REPEAT('bla bla', 100) AS body) t1;
 
 #
 ## TODO: add tests for all engines

mysql-test/t/ctype_utf8.test

@@ -1590,6 +1590,11 @@ SELECT 'a' AS id, REPEAT('bla bla', 100) AS body) t1
 GROUP BY id
 ORDER BY l DESC;
 
+SELECT id, CHAR_LENGTH(GROUP_CONCAT(body)) AS l
+FROM (SELECT 'a' AS id, REPEAT('foo bar', 100) AS body
+UNION ALL
+SELECT 'a' AS id, REPEAT('bla bla', 100) AS body) t1;
+
 --echo #
 --echo # End of 5.5 tests
 --echo #

mysql-test/t/func_gconcat.test

@@ -375,7 +375,7 @@ select group_concat('x') UNION ALL select 1;
 drop table t1;
 
 #
-# Bug #12863 : missing separators after first empty cancatanated elements
+# Bug #12863 : missing separators after first empty concatenated elements
 #
 
 CREATE TABLE t1 (id int, a varchar(9));

sql/item.cc

@@ -5579,7 +5579,7 @@ bool Item::eq_by_collation(Item *item, bool binary_cmp, CHARSET_INFO *cs)
 /**
   Create a field to hold a string value from an item.
 
-  If max_length > CONVERT_IF_BIGGER_TO_BLOB create a blob @n
+  If too_big_for_varchar() create a blob @n
   If max_length > 0 create a varchar @n
   If max_length == 0 create a CHAR(0) 
 
@@ -5594,7 +5594,7 @@ Field *Item::make_string_field(TABLE *table)
     Note: the following check is repeated in 
     subquery_types_allow_materialization():
   */
-  if (max_length/collation.collation->mbmaxlen > CONVERT_IF_BIGGER_TO_BLOB)
+  if (too_big_for_varchar())
     field= new Field_blob(max_length, maybe_null, name,
                           collation.collation, TRUE);
   /* Item_type_holder holds the exact type, do not change it */
@@ -5699,7 +5699,7 @@ Field *Item::tmp_table_field_from_field_type(TABLE *table, bool fixed_length)
     DBUG_ASSERT(0);
     /* If something goes awfully wrong, it's better to get a string than die */
   case MYSQL_TYPE_STRING:
-    if (fixed_length && max_length < CONVERT_IF_BIGGER_TO_BLOB)
+    if (fixed_length && !too_big_for_varchar())
     {
       field= new Field_string(max_length, maybe_null, name,
                               collation.collation);

sql/item.h

@@ -1424,6 +1424,8 @@ class Item {
   bool eq_by_collation(Item *item, bool binary_cmp, CHARSET_INFO *cs); 
   uint32 max_char_length() const
   { return max_length / collation.collation->mbmaxlen; }
+  bool too_big_for_varchar() const
+  { return max_char_length() > CONVERT_IF_BIGGER_TO_BLOB; }
   void fix_length_and_charset(uint32 max_char_length_arg, CHARSET_INFO *cs)
   {
     max_length= char_to_byte_length_safe(max_char_length_arg, cs->mbmaxlen);

sql/item_sum.h

@@ -1439,7 +1439,7 @@ class Item_func_group_concat : public Item_sum
   virtual Field *make_string_field(TABLE *table);
   enum_field_types field_type() const
   {
-    if (max_length/collation.collation->mbmaxlen > CONVERT_IF_BIGGER_TO_BLOB )
+    if (too_big_for_varchar())
       return MYSQL_TYPE_BLOB;
     else
       return MYSQL_TYPE_VARCHAR;

sql/opt_subselect.cc

@@ -853,8 +853,7 @@ bool subquery_types_allow_materialization(Item_in_subselect *in_subs)
         create a blob column because item->max_length is too big.
         The following check is copied from Item::make_string_field():
       */ 
-      if (inner->max_length / inner->collation.collation->mbmaxlen > 
-          CONVERT_IF_BIGGER_TO_BLOB)
+      if (inner->too_big_for_varchar())
       {
         DBUG_RETURN(FALSE);
       }
@@ -3865,6 +3864,7 @@ SJ_TMP_TABLE::create_sj_weedout_tmp_table(THD *thd)
   fn_format(path, path, mysql_tmpdir, "", MY_REPLACE_EXT|MY_UNPACK_FILENAME);
 
   /* STEP 2: Figure if we'll be using a key or blob+constraint */
+  /* it always has my_charset_bin, so mbmaxlen==1 */
   if (uniq_tuple_length_arg >= CONVERT_IF_BIGGER_TO_BLOB)
     using_unique_constraint= TRUE;
 

sql/sql_const.h

@@ -42,8 +42,8 @@
 #define MAX_MBWIDTH		3		/* Max multibyte sequence */
 #define MAX_FIELD_CHARLENGTH	255
 #define MAX_FIELD_VARCHARLENGTH	65535
-#define MAX_FIELD_BLOBLENGTH UINT_MAX32     /* cf field_blob::get_length() */
-#define CONVERT_IF_BIGGER_TO_BLOB 512		/* Used for CREATE ... SELECT */
+#define MAX_FIELD_BLOBLENGTH UINT_MAX32         /* cf field_blob::get_length() */
+#define CONVERT_IF_BIGGER_TO_BLOB 512           /* Threshold *in characters*   */
 
 /* Max column width +1 */
 #define MAX_FIELD_WIDTH		(MAX_FIELD_CHARLENGTH*MAX_MBWIDTH+1)

sql/sql_select.cc

@@ -14185,7 +14185,7 @@ create_tmp_table(THD *thd, TMP_TABLE_PARAM *param, List<Item> &fields,
           can't index BIT fields.
       */
       (*tmp->item)->marker=4;			// Store null in key
-      if ((*tmp->item)->max_length >= CONVERT_IF_BIGGER_TO_BLOB)
+      if ((*tmp->item)->too_big_for_varchar())
 	using_unique_constraint=1;
     }
     if (param->group_length >= MAX_BLOB_WIDTH)