Bug#54916 GROUP_CONCAT + IFNULL truncates output

Problem: a few functions did not calculate their max_length correctly.
This is an after-fix for WL#2649 Number-to-string conversions".

Fix: changing the buggy functions to calculate max_length
using fix_char_length() introduced in WL#2649,
instead of setting max_length directly

  mysql-test/include/ctype_numconv.inc
     Adding new tests

  mysql-test/r/ctype_binary.result
     Adding new tests

  mysql-test/r/ctype_cp1251.result
     Adding new tests

  mysql-test/r/ctype_latin1.result
     Adding new tests

  mysql-test/r/ctype_ucs.result
     Adding new tests

  mysql-test/r/ctype_utf8.result
     Adding new tests

  mysql-test/t/ctype_utf8.test
    Including ctype_numconv

  sql/item.h
    - Introducing new method fix_char_length_ulonglong(),
    for the cases when length is potentially greater
    than UINT_MAX32. This method removes a few
    instances of duplicate code, e.g. in item_strfunc.cc.
    - Setting collation in Item_copy properly. This change
    fixes wrong metadata on client side in some cases, when
    "binary" instead of the real character set was reported.

  sql/item_cmpfunc.cc
    - Using fix_char_length() and max_char_length() methods,
    instead of direct access to max_length, to calculate
    item length properly.
    - Moving count_only_length() in COALESCE after
    agg_arg_charsets_for_string_result(). The old
    order was incorrect and led to wrong length
    calucation in case of multi-byte character sets.
    
  sql/item_func.cc
    Fixing that count_only_length() didn't work
    properly for multi-byte character sets.
    Using fix_char_length() and max_char_length()
    instead of direct access to max_length.

  sql/item_strfunc.cc
    - Using fix_char_length(), fix_char_length_ulonglong(),
    max_char_length() instead of direct access to max_length.
    - Removing wierd condition: "if (collation.collation->mbmaxlen > 0)",
    which is never FALSE.

1 files changed, 14 insertions, 1 deletions

diff --git a/sql/item.h b/sql/item.h
index 3af33fd2d31..8e8199ecac8 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -547,7 +547,7 @@ public:
      @see Query_arena::free_list
    */
   Item *next;
-  uint32 max_length;
+  uint32 max_length;                    /* Maximum length, in bytes */
   uint name_length;                     /* Length of name */
   int8 marker;
   uint8 decimals;
@@ -1221,6 +1221,18 @@ public:
     max_length= char_to_byte_length_safe(max_char_length_arg,
                                          collation.collation->mbmaxlen);
   }
+  void fix_char_length_ulonglong(ulonglong max_char_length_arg)
+  {
+    ulonglong max_result_length= max_char_length_arg *
+                                 collation.collation->mbmaxlen;
+    if (max_result_length >= MAX_BLOB_WIDTH)
+    {
+      max_length= MAX_BLOB_WIDTH;
+      maybe_null= 1;
+    }
+    else
+      max_length= max_result_length;
+  }
   void fix_length_and_charset_datetime(uint32 max_char_length_arg)
   {
     collation.set(&my_charset_numeric, DERIVATION_NUMERIC, MY_REPERTOIRE_ASCII);
@@ -2825,6 +2837,7 @@ protected:
     cached_result_type= item->result_type();
     unsigned_flag= item->unsigned_flag;
     fixed= item->fixed;
+    collation.set(item->collation);
   }
 
 public: