MDEV-26129 Bad results with join comparing case insensitive VARCHAR/E…

…NUM/SET expression to a _bin ENUM column

Range optimizer incorrectly was used for ENUM columns
when the operation collation did not match the column collation.

Adding a virtual implementation of Field_enum::can_optimize_range()
which tests if the column and the operation collation match.

mysql-test/r/type_enum.result

@@ -2219,3 +2219,24 @@ SELECT * FROM t1;
 a
 
 DROP TABLE t1;
+#
+# MDEV-26129 Bad results with join comparing case insensitive VARCHAR/ENUM/SET expression to a _bin ENUM column
+#
+CREATE TABLE t1 (a ENUM('a') CHARACTER SET latin1 PRIMARY KEY);
+INSERT INTO t1 VALUES ('a');
+CREATE TABLE t2 (a ENUM('a','A','b','B','c','C','d','D','e','E') CHARACTER SET latin1 COLLATE latin1_bin);
+INSERT INTO t2 VALUES ('a'),('A');
+INSERT INTO t2 VALUES ('b'),('B'),('c'),('C'),('d'),('D'),('e'),('E');
+ALTER TABLE t2 ADD PRIMARY KEY(a);
+SELECT t1.a res FROM t1 JOIN t2 ON t1.a COLLATE latin1_swedish_ci=t2.a;
+res
+a
+a
+SELECT t1.a res FROM t1 LEFT JOIN t2 ON t1.a COLLATE latin1_swedish_ci=t2.a;
+res
+a
+a
+DROP TABLE IF EXISTS t1,t2;
+#
+# End of 10.2. tests
+#

mysql-test/t/type_enum.test

@@ -454,3 +454,23 @@ SET STATEMENT sql_mode = 'NO_ENGINE_SUBSTITUTION' FOR
 ALTER TABLE t1 MODIFY a ENUM('2001','2002');
 SELECT * FROM t1;
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-26129 Bad results with join comparing case insensitive VARCHAR/ENUM/SET expression to a _bin ENUM column
+--echo #
+
+CREATE TABLE t1 (a ENUM('a') CHARACTER SET latin1 PRIMARY KEY);
+INSERT INTO t1 VALUES ('a');
+CREATE TABLE t2 (a ENUM('a','A','b','B','c','C','d','D','e','E') CHARACTER SET latin1 COLLATE latin1_bin);
+INSERT INTO t2 VALUES ('a'),('A');
+# without the following insert the bug doesn't show, was fixed in MDEV-6978
+INSERT INTO t2 VALUES ('b'),('B'),('c'),('C'),('d'),('D'),('e'),('E');
+ALTER TABLE t2 ADD PRIMARY KEY(a);
+SELECT t1.a res FROM t1 JOIN t2 ON t1.a COLLATE latin1_swedish_ci=t2.a;
+SELECT t1.a res FROM t1 LEFT JOIN t2 ON t1.a COLLATE latin1_swedish_ci=t2.a;
+DROP TABLE IF EXISTS t1,t2;
+
+
+--echo #
+--echo # End of 10.2. tests
+--echo #

sql/field.cc

@@ -9484,8 +9484,8 @@ uint Field_num::is_equal(Create_field *new_field)
 }
 
 
-bool Field_enum::can_optimize_keypart_ref(const Item_bool_func *cond,
-                                          const Item *item) const
+bool Field_enum::can_optimize_range_or_keypart_ref(const Item_bool_func *cond,
+                                                   const Item *item) const
 {
   DBUG_ASSERT(cmp_type() == INT_RESULT);
   DBUG_ASSERT(result_type() == STRING_RESULT);

sql/field.h

@@ -3623,6 +3623,8 @@ uint gis_field_options_read(const uchar *buf, uint buf_len,
 
 class Field_enum :public Field_str {
   static void do_field_enum(Copy_field *copy_field);
+  bool can_optimize_range_or_keypart_ref(const Item_bool_func *cond,
+                                         const Item *item) const;
 protected:
   uint packlength;
 public:
@@ -3700,7 +3702,10 @@ class Field_enum :public Field_str {
                               const uchar *from_end, uint param_data);
 
   bool can_optimize_keypart_ref(const Item_bool_func *cond,
-                                const Item *item) const;
+                                const Item *item) const
+  {
+    return can_optimize_range_or_keypart_ref(cond, item);
+  }
   bool can_optimize_group_min_max(const Item_bool_func *cond,
                                   const Item *const_item) const
   {
@@ -3713,6 +3718,12 @@ class Field_enum :public Field_str {
     */
     return false;
   }
+  bool can_optimize_range(const Item_bool_func *cond,
+                          const Item *item,
+                          bool is_eq_func) const
+  {
+    return can_optimize_range_or_keypart_ref(cond, item);
+  }
 private:
   int do_save_field_metadata(uchar *first_byte);
   uint is_equal(Create_field *new_field);