MDEV-17411 Wrong WHERE optimization with simple CASE and searched CASE

mysql-test/main/case.result

@@ -546,5 +546,32 @@ Warnings:
 Note	1003	select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 'a'
 DROP TABLE t1;
 #
+# MDEV-17411 Wrong WHERE optimization with simple CASE and searched CASE
+#
+CREATE TABLE t1 (a INT, b INT, KEY(a));
+INSERT INTO t1 VALUES (1,1),(2,2),(3,3);
+SELECT * FROM t1 WHERE CASE a WHEN b THEN 1 END=1;
+a	b
+1	1
+2	2
+3	3
+SELECT * FROM t1 WHERE CASE WHEN a THEN b ELSE 1 END=3;
+a	b
+3	3
+SELECT * FROM t1 WHERE
+CASE      a WHEN b THEN 1 END=1 AND
+CASE WHEN a THEN b ELSE 1 END=3;
+a	b
+3	3
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE
+CASE      a WHEN b THEN 1 END=1 AND
+CASE WHEN a THEN b ELSE 1 END=3;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	100.00	Using where
+Warnings:
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b` from `test`.`t1` where (case `test`.`t1`.`a` when `test`.`t1`.`b` then 1 end) = 1 and (case when `test`.`t1`.`a` then `test`.`t1`.`b` else 1 end) = 3
+DROP TABLE t1;
+#
 # End of 10.3 test
 #

mysql-test/main/case.test

@@ -390,6 +390,28 @@ EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='a' AND CASE 'a' WHEN 'a' THEN 'a' ELS
 
 DROP TABLE t1;
 
+
+--echo #
+--echo # MDEV-17411 Wrong WHERE optimization with simple CASE and searched CASE
+--echo #
+
+CREATE TABLE t1 (a INT, b INT, KEY(a));
+INSERT INTO t1 VALUES (1,1),(2,2),(3,3);
+SELECT * FROM t1 WHERE CASE a WHEN b THEN 1 END=1;
+SELECT * FROM t1 WHERE CASE WHEN a THEN b ELSE 1 END=3;
+
+SELECT * FROM t1 WHERE
+  CASE      a WHEN b THEN 1 END=1 AND
+  CASE WHEN a THEN b ELSE 1 END=3;
+
+EXPLAIN EXTENDED
+SELECT * FROM t1 WHERE
+  CASE      a WHEN b THEN 1 END=1 AND
+  CASE WHEN a THEN b ELSE 1 END=3;
+
+DROP TABLE t1;
+
+
 --echo #
 --echo # End of 10.3 test
 --echo #

sql/item.h

@@ -2211,6 +2211,15 @@ class Item_args
     }
     return true;
   }
+  bool eq(const Item_args *other, bool binary_cmp) const
+  {
+    for (uint i= 0; i < arg_count ; i++)
+    {
+      if (!args[i]->eq(other->args[i], binary_cmp))
+        return false;
+    }
+    return true;
+  }
 public:
   Item_args(void)
     :args(NULL), arg_count(0)

sql/item_cmpfunc.cc

@@ -1813,10 +1813,7 @@ bool Item_func_opt_neg::eq(const Item *item, bool binary_cmp) const
     return 0;
   if (negated != ((Item_func_opt_neg *) item_func)->negated)
     return 0;
-  for (uint i=0; i < arg_count ; i++)
-    if (!args[i]->eq(item_func->arguments()[i], binary_cmp))
-      return 0;
-  return 1;
+  return Item_args::eq(item_func, binary_cmp);
 }
 
 

sql/item_cmpfunc.h

@@ -2154,6 +2154,7 @@ class Item_func_case_searched: public Item_func_case
     DBUG_ASSERT(arg_count >= 2);
     reorder_args(0);
   }
+  enum Functype functype() const   { return CASE_SEARCHED_FUNC; }
   void print(String *str, enum_query_type query_type);
   bool fix_length_and_dec();
   Item *propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond)
@@ -2206,6 +2207,7 @@ class Item_func_case_simple: public Item_func_case,
     Predicant_to_list_comparator::cleanup();
     DBUG_VOID_RETURN;
   }
+  enum Functype functype() const   { return CASE_SIMPLE_FUNC; }
   void print(String *str, enum_query_type query_type);
   bool fix_length_and_dec();
   Item *propagate_equal_fields(THD *thd, const Context &ctx, COND_EQUAL *cond);

sql/item_func.cc

@@ -647,10 +647,7 @@ bool Item_func::eq(const Item *item, bool binary_cmp) const
       (func_type == Item_func::FUNC_SP &&
        my_strcasecmp(system_charset_info, func_name(), item_func->func_name())))
     return 0;
-  for (uint i=0; i < arg_count ; i++)
-    if (!args[i]->eq(item_func->args[i], binary_cmp))
-      return 0;
-  return 1;
+  return Item_args::eq(item_func, binary_cmp);
 }
 
 

sql/item_func.h

@@ -76,7 +76,10 @@ class Item_func :public Item_func_or_sum
                   SUSERVAR_FUNC, GUSERVAR_FUNC, COLLATE_FUNC,
                   EXTRACT_FUNC, CHAR_TYPECAST_FUNC, FUNC_SP, UDF_FUNC,
                   NEG_FUNC, GSYSVAR_FUNC, IN_OPTIMIZER_FUNC, DYNCOL_FUNC,
-                  JSON_EXTRACT_FUNC };
+                  JSON_EXTRACT_FUNC,
+                  CASE_SEARCHED_FUNC, // Used by ColumnStore/Spider
+                  CASE_SIMPLE_FUNC    // Used by ColumnStore/spider
+                };
   enum Type type() const { return FUNC_ITEM; }
   virtual enum Functype functype() const   { return UNKNOWN_FUNC; }
   Item_func(THD *thd): Item_func_or_sum(thd)