Bug#57306 SHOW PROCESSLIST does not display string literals well.

Problem: Extended characters outside of ASCII range where not displayed
properly in SHOW PROCESSLIST, because thd_info->query was always sent as 
system_character_set (utf8). This was wrong, because query buffer
is never converted to utf8 - it is always have client character set.

Fix: sending query buffer using query character set

  @ sql/sql_class.cc
  @ sql/sql_class.h
    Introducing a new class CSET_STRING, a LEX_STRING with character set.
    Adding set_query(&CSET_STRING)
    Adding reset_query(), to use instead of set_query(0, NULL).

  @ sql/event_data_objects.cc
    Using reset_query()

  @ sql/log_event.cc
    Using reset_query()
    Adding charset argument to set_query_and_id().

  @ sql/slave.cc
    Using reset_query().

  @ sql/sp_head.cc
    Changing backing up and restore code to use CSET_STRING.

  @ sql/sql_audit.h
    Using CSET_STRING.
    In the "else" branch it's OK not to use
    global_system_variables.character_set_client.
    &my_charset_latin1, which is set in constructor, is fine
    (verified with Sergey Vojtovich).

  @ sql/sql_insert.cc
    Using set_query() with proper character set: table_name is utf8.

  @ sql/sql_parse.cc
    Adding character set argument to set_query_and_id().
    (This is the main point where thd->charset() is stored
     into thd->query_string.cs, for use in "SHOW PROCESSLIST".)
    Using reset_query().
    
  @ sql/sql_prepare.cc
    Storing client character set into thd->query_string.cs.

  @ sql/sql_show.cc
    Using CSET_STRING to fetch and send charset-aware query information
    from threads.

  @ storage/myisam/ha_myisam.cc
    Using set_query() with proper character set: table_name is utf8.

  @ mysql-test/r/show_check.result
  @ mysql-test/t/show_check.test
    Adding tests

1 files changed, 3 insertions, 6 deletions

diff --git a/storage/myisam/ha_myisam.cc b/storage/myisam/ha_myisam.cc
index 2ba62d03c6b..c4bb6d7dbd4 100644
--- a/storage/myisam/ha_myisam.cc
+++ b/storage/myisam/ha_myisam.cc
@@ -1499,8 +1499,6 @@ bool ha_myisam::check_and_repair(THD *thd)
 {
   int error=0;
   int marked_crashed;
-  char *old_query;
-  uint old_query_length;
   HA_CHECK_OPT check_opt;
   DBUG_ENTER("ha_myisam::check_and_repair");
 
@@ -1511,10 +1509,9 @@ bool ha_myisam::check_and_repair(THD *thd)
     check_opt.flags|=T_QUICK;
   sql_print_warning("Checking table:   '%s'",table->s->path.str);
 
-  old_query= thd->query();
-  old_query_length= thd->query_length();
+  const CSET_STRING query_backup= thd->query_string;
   thd->set_query(table->s->table_name.str,
-                 (uint) table->s->table_name.length);
+                 (uint) table->s->table_name.length, system_charset_info);
 
   if ((marked_crashed= mi_is_crashed(file)) || check(thd, &check_opt))
   {
@@ -1527,7 +1524,7 @@ bool ha_myisam::check_and_repair(THD *thd)
     if (repair(thd, &check_opt))
       error=1;
   }
-  thd->set_query(old_query, old_query_length);
+  thd->set_query(query_backup);
   DBUG_RETURN(error);
 }