MDEV-8723 Wrong result for SELECT..WHERE COLLATION(a)='binary' AND a='a'

mysql-test/r/ctype_binary.result

@@ -3101,5 +3101,43 @@ Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 'a ')
 DROP TABLE t1;
 #
+# MDEV-8723 Wrong result for SELECT..WHERE COLLATION(a)='binary' AND a='a'
+#
+CREATE TABLE t1 (a VARBINARY(10));
+INSERT INTO t1 VALUES ('a'),('A');
+SELECT * FROM t1 WHERE COLLATION(a)='binary' AND a='a';
+a
+a
+SELECT * FROM t1 WHERE CHARSET(a)='binary' AND a='a';
+a
+a
+SELECT * FROM t1 WHERE COERCIBILITY(a)=2 AND a='a';
+a
+a
+SELECT * FROM t1 WHERE WEIGHT_STRING(a)='a' AND a='a';
+a
+a
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE COLLATION(a)='binary' AND a='a';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 'a')
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE CHARSET(a)='binary'   AND a='a';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 'a')
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE COERCIBILITY(a)=2     AND a='a';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 'a')
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE WEIGHT_STRING(a)='a'  AND a='a';
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = 'a') and (weight_string(`test`.`t1`.`a`) = 'a'))
+DROP TABLE t1;
+#
 # End of 10.1 tests
 #

mysql-test/t/ctype_binary.test

@@ -56,6 +56,21 @@ SELECT * FROM t1 WHERE a='a ' AND LENGTH(a)=2;
 EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='a ' AND LENGTH(a)=2;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-8723 Wrong result for SELECT..WHERE COLLATION(a)='binary' AND a='a'
+--echo #
+CREATE TABLE t1 (a VARBINARY(10));
+INSERT INTO t1 VALUES ('a'),('A');
+SELECT * FROM t1 WHERE COLLATION(a)='binary' AND a='a';
+SELECT * FROM t1 WHERE CHARSET(a)='binary' AND a='a';
+SELECT * FROM t1 WHERE COERCIBILITY(a)=2 AND a='a';
+SELECT * FROM t1 WHERE WEIGHT_STRING(a)='a' AND a='a';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE COLLATION(a)='binary' AND a='a';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE CHARSET(a)='binary'   AND a='a';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE COERCIBILITY(a)=2     AND a='a';
+EXPLAIN EXTENDED SELECT * FROM t1 WHERE WEIGHT_STRING(a)='a'  AND a='a';
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.1 tests
 --echo #

sql/item_func.h

@@ -1160,6 +1160,9 @@ class Item_func_coercibility :public Item_int_func
   const char *func_name() const { return "coercibility"; }
   void fix_length_and_dec() { max_length=10; maybe_null= 0; }
   table_map not_null_tables() const { return 0; }
+  Item* propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond)
+  { return this; }
+  bool const_item() const { return true; }
 };
 
 class Item_func_locate :public Item_int_func

sql/item_strfunc.h

@@ -1049,12 +1049,11 @@ class Item_func_set_collation :public Item_str_func
   }
 };
 
-class Item_func_charset :public Item_str_func
+
+class Item_func_expr_str_metadata :public Item_str_func
 {
 public:
-  Item_func_charset(THD *thd, Item *a): Item_str_func(thd, a) {}
-  String *val_str(String *);
-  const char *func_name() const { return "charset"; }
+  Item_func_expr_str_metadata(THD *thd, Item *a): Item_str_func(thd, a) { }
   void fix_length_and_dec()
   {
      collation.set(system_charset_info);
@@ -1062,23 +1061,32 @@ class Item_func_charset :public Item_str_func
      maybe_null= 0;
   };
   table_map not_null_tables() const { return 0; }
+  Item* propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond)
+  { return this; }
+  bool const_item() const { return true; }
 };
 
-class Item_func_collation :public Item_str_func
+
+class Item_func_charset :public Item_func_expr_str_metadata
 {
 public:
-  Item_func_collation(THD *thd, Item *a): Item_str_func(thd, a) {}
+  Item_func_charset(THD *thd, Item *a)
+    :Item_func_expr_str_metadata(thd, a) { }
+  String *val_str(String *);
+  const char *func_name() const { return "charset"; }
+};
+
+
+class Item_func_collation :public Item_func_expr_str_metadata
+{
+public:
+  Item_func_collation(THD *thd, Item *a)
+    :Item_func_expr_str_metadata(thd, a) {}
   String *val_str(String *);
   const char *func_name() const { return "collation"; }
-  void fix_length_and_dec()
-  {
-     collation.set(system_charset_info);
-     max_length= 64 * collation.collation->mbmaxlen; // should be enough
-     maybe_null= 0;
-  };
-  table_map not_null_tables() const { return 0; }
 };
 
+
 class Item_func_weight_string :public Item_str_func
 {
   String tmp_value;
@@ -1106,6 +1114,8 @@ class Item_func_weight_string :public Item_str_func
            this->nweights == that->nweights &&
            this->result_length == that->result_length;
   }
+  Item* propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond)
+  { return this; }
 };
 
 class Item_func_crc32 :public Item_int_func