Bug#31384 DATE_ADD() and DATE_SUB() return binary data

Problem: DATE_ADD() is a hybrid function and can return
DATE, DATETIME or VARCHAR data type depending on arguments.

In case of VARCHAR data type, DATE_ADD() reported "binary" character set,
which was wrong.

Fix: make DATE_ADD() return @character_set_connection in VARCHAR context.
 @ mysql-test/include/ctype_numconv.inc
   Adding tests
 @ mysql-test/r/ctype_binary.result
   Adding tests
 @ mysql-test/r/ctype_cp1251.result
   Adding tests
 @ mysql-test/r/ctype_latin1.result
   Adding tests
 @ mysql-test/r/ctype_ucs.result
   Adding tests
 @ mysql-test/r/ctype_utf8.result
   Adding tests
 @ sql/item_strfunc.cc
  - Moving code from Item_str_ascii_func::val_str() to
  Item_str_func::val_str_from_val_str_ascii(), as
  this code needs to be shared by Item_date_add_interval.
  - Adding str2 parameter to be used as a buffer, instead of
   using private ascii_buf member.
 @ sql/item_strfunc.h
  - Moving code from Item_str_ascii_func::val_str() to
  Item_str_func::val_str_from_val_str_ascii()
  - Removing "String *val_str_convert_from_ascii(String *str, String *ascii_buf)"
    prototype as it was neither used nor declared.
 @ sql/item_timefunc.h
  - Overwriting parent's charset_for_protocol() method,
    becase we need to behave differenlty in VARCHAR and DATE/DATETYPE context.
  - Adding ascii_buf for conversion.
  - Adding val_str_ascii() prototype.
  - Adding val_str() which uses newly added
    Item_str_func::val_str_from_val_str_ascii(),
    passing ascii_buf as a conversion buffer.

1 files changed, 18 insertions, 2 deletions

diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index b8c6b1d38e4..9732e8dc360 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -773,16 +773,32 @@ class Item_date_add_interval :public Item_date_func
 {
   String value;
   enum_field_types cached_field_type;
-
+  String ascii_buf;
 public:
   const interval_type int_type; // keep it public
   const bool date_sub_interval; // keep it public
   Item_date_add_interval(Item *a,Item *b,interval_type type_arg,bool neg_arg)
     :Item_date_func(a,b),int_type(type_arg), date_sub_interval(neg_arg) {}
-  String *val_str(String *);
+  String *val_str_ascii(String *str);
+  String *val_str(String *str)
+  {
+    return val_str_from_val_str_ascii(str, &ascii_buf);
+  }
   const char *func_name() const { return "date_add_interval"; }
   void fix_length_and_dec();
   enum_field_types field_type() const { return cached_field_type; }
+  CHARSET_INFO *charset_for_protocol(void) const
+  {
+    /*
+      DATE_ADD() can return DATE, DATETIME or VARCHAR depending on arguments.
+      Send using "binary" when DATE or DATETIME,
+      or using collation.collation when VARCHAR
+      (which was fixed from @collation_connection in fix_length_and_dec).
+    */
+    DBUG_ASSERT(fixed == 1);
+    return cached_field_type == MYSQL_TYPE_STRING ?
+                                collation.collation : &my_charset_bin;
+  }
   longlong val_int();
   bool get_date(MYSQL_TIME *res, uint fuzzy_date);
   bool eq(const Item *item, bool binary_cmp) const;