Bug#11764503 (Bug#57341) Query in EXPLAIN EXTENDED shows wrong characters

  @ mysql-test/r/ctype_latin1.result
  @ mysql-test/r/ctype_utf8.result
  @ mysql-test/t/ctype_latin1.test
  @ mysql-test/t/ctype_utf8.test
  Adding tests

  @ sql/mysqld.h
  @ sql/item.cc
  @ sql/sql_parse.cc
  @ sql/sql_view.cc

  Refactoring (thanks to Guilhem for the idea):

  Item_string::print() was hard to understand because of the different
  QT_ constants: in "query_type==QT_x", QT_x is explicitely included
  but the other two QT_ are implicitely excluded. The combinations
  with '||' and '&&' make this even harder.
  - logic is now more "explicit" by changing QT_ constants to a bitmap of flags:
    QT_ORDINARY: no change,
    QT_IS -> QT_TO_SYSTEM_CHARSET | QT_WITHOUT_INTRODUCERS,
    QT_EXPLAIN -> QT_TO_SYSTEM_CHARSET
    (QT_EXPLAIN was introduced in the first version of the Bug#57341 patch)
  - Item_string::print() is rewritten using those flags

  Bugfix itself:

  When QT_TO_SYSTEM_CHARSET is used alone (with no QT_WITHOUT_INTRODUCERS),
  we print string literals as follows:

  - display introducers if they were in the original query
  - print ASCII characters as is
  - print non-ASCII characters using hex-escape
  Note: as "EXPLAIN" output is only for human readability purposes
  and does not need to be a pasrable SQL, so using hex-escape is Ok.
  ErrConvString class perfectly suites for hex escaping purposes.

1 files changed, 7 insertions, 7 deletions

diff --git a/sql/mysqld.h b/sql/mysqld.h
index 2099e57e96d..5af1260ecbc 100644
--- a/sql/mysqld.h
+++ b/sql/mysqld.h
@@ -399,16 +399,16 @@ enum options_mysqld
 
 
 /**
-  Query type constants.
-
-  QT_ORDINARY -- ordinary SQL query.
-  QT_IS -- SQL query to be shown in INFORMATION_SCHEMA (in utf8 and without
-  character set introducers).
+   Query type constants (usable as bitmap flags).
 */
 enum enum_query_type
 {
-  QT_ORDINARY,
-  QT_IS
+  /// Nothing specific, ordinary SQL query.
+  QT_ORDINARY= 0,
+  /// In utf8.
+  QT_TO_SYSTEM_CHARSET= (1 << 0),
+  /// Without character set introducers.
+  QT_WITHOUT_INTRODUCERS= (1 << 1)
 };
 
 /* query_id */