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, 2 insertions, 0 deletions

diff --git a/mysql-test/r/case.result b/mysql-test/r/case.result
index fcbf5812312..40d900a0389 100644
--- a/mysql-test/r/case.result
+++ b/mysql-test/r/case.result
@@ -160,6 +160,8 @@ t1	CREATE TABLE `t1` (
   `COALESCE('a' COLLATE latin1_bin,'b')` varchar(1) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL DEFAULT ''
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 DROP TABLE t1;
+CREATE TABLE t1 SELECT IFNULL('a' COLLATE latin1_swedish_ci, 'b' COLLATE latin1_bin);
+ERROR HY000: Illegal mix of collations (latin1_swedish_ci,EXPLICIT) and (latin1_bin,EXPLICIT) for operation 'ifnull'
 SELECT 'case+union+test'
 UNION 
 SELECT CASE LOWER('1') WHEN LOWER('2') THEN 'BUG' ELSE 'nobug' END;