Bug #26881946: INCORRECT BEHAVIOR WITH "VALUES"

Issue:
------
VALUES doesn't have a type() function and is considered a
Item_field.

Solution for 5.7:
-----------------
Add a new type() function for Item_values_insert.

On 8.0 and trunk it was fixed by Mithun's Bug#19601973.

Solution for 5.6:
-----------------
Additionally Bug#17458914 is backported.

This will address the problem of using VALUES() in
INSERT ... ON DUPLICATE KEY UPDATE. Create a field object
only if it is in the UPDATE clause, else return a NULL
item.

This will also address the problems mentioned in
Bug#14789787 and Bug#16756402.

Solution for 5.5:
-----------------
As mentioned above Bug#17458914 is backported.

Additionally Bug#14786324 is also backported.

When VALUES() is detected outside its meaningful place,
it should be treated as NULL and is thus replaced with a
Field_null object, with the same name as the original
field.

Fields with type NULL are generally not handled well inside
the server (e.g Innodb will not accept them and it is
impossible to create them in regular tables). So create a
new const NULL item instead.

mysql-test/r/insert_update.result

@@ -60,12 +60,12 @@ explain extended SELECT *, VALUES(a) FROM t1;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	
 Warnings:
-Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t1`.`c` AS `c`,values(`test`.`t1`.`a`) AS `VALUES(a)` from `test`.`t1`
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t1`.`c` AS `c`,NULL AS `VALUES(a)` from `test`.`t1`
 explain extended select * from t1 where values(a);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	5	100.00	Using where
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE
 Warnings:
-Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t1`.`c` AS `c` from `test`.`t1` where values(`test`.`t1`.`a`)
+Note	1003	select `test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t1`.`c` AS `c` from `test`.`t1` where 0
 DROP TABLE t1;
 create table t1(a int primary key, b int);
 insert into t1 values(1,1),(2,2),(3,3),(4,4),(5,5);

sql/item.cc

@@ -7120,7 +7120,7 @@ Item *Item_default_value::transform(Item_transformer transformer, uchar *args)
 bool Item_insert_value::eq(const Item *item, bool binary_cmp) const
 {
   return item->type() == INSERT_VALUE_ITEM &&
-    ((Item_default_value *)item)->arg->eq(arg, binary_cmp);
+    ((Item_insert_value *)item)->arg->eq(arg, binary_cmp);
 }
 
 
@@ -7149,11 +7149,12 @@ bool Item_insert_value::fix_fields(THD *thd, Item **items)
 
   Item_field *field_arg= (Item_field *)arg;
 
-  if (field_arg->field->table->insert_values)
+  if (field_arg->field->table->insert_values &&
+      thd->lex->in_update_value_clause)
   {
     Field *def_field= (Field*) sql_alloc(field_arg->field->size_of());
     if (!def_field)
-      return TRUE;
+      return true;
     memcpy(def_field, field_arg->field, field_arg->field->size_of());
     def_field->move_field_offset((my_ptrdiff_t)
                                  (def_field->table->insert_values -
@@ -7162,17 +7163,17 @@ bool Item_insert_value::fix_fields(THD *thd, Item **items)
   }
   else
   {
-    Field *tmp_field= field_arg->field;
-    /* charset doesn't matter here, it's to avoid sigsegv only */
-    tmp_field= new Field_null(0, 0, Field::NONE, field_arg->field->field_name,
-                          &my_charset_bin);
-    if (tmp_field)
-    {
-      tmp_field->init(field_arg->field->table);
-      set_field(tmp_field);
-    }
+    // VALUES() is used out-of-scope - its value is always NULL
+    Query_arena backup;
+    Query_arena *const arena= thd->activate_stmt_arena_if_needed(&backup);
+    Item *const item= new Item_null(this->name);
+    if (arena)
+      thd->restore_active_arena(arena, &backup);
+    if (!item)
+      return TRUE;
+    *items= item;
   }
-  return FALSE;
+  return false;
 }
 
 void Item_insert_value::print(String *str, enum_query_type query_type)

sql/item.h

@@ -3150,6 +3150,8 @@ class Item_insert_value : public Item_field
     :Item_field(context_arg, (const char *)NULL, (const char *)NULL,
                (const char *)NULL),
      arg(a) {}
+
+  enum Type type() const { return INSERT_VALUE_ITEM; }
   bool eq(const Item *item, bool binary_cmp) const;
   bool fix_fields(THD *, Item **);
   virtual void print(String *str, enum_query_type query_type);

sql/sql_insert.cc

 /*
-   Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -1393,9 +1393,12 @@ bool mysql_prepare_insert(THD *thd, TABLE_LIST *table_list,
       thd->abort_on_warning= saved_abort_on_warning;
     }
 
+   thd->lex->in_update_value_clause= true;
    if (!res)
      res= setup_fields(thd, 0, update_values, MARK_COLUMNS_READ, 0, 0);
 
+    thd->lex->in_update_value_clause= false;
+
     if (!res && duplic == DUP_UPDATE)
     {
       select_lex->no_wrap_view_item= TRUE;
@@ -3263,8 +3266,11 @@ select_insert::prepare(List<Item> &values, SELECT_LEX_UNIT *u)
       table_list->next_name_resolution_table= 
         ctx_state.get_first_name_resolution_table();
 
+    thd->lex->in_update_value_clause= true;
     res= res || setup_fields(thd, 0, *info.update_values,
                              MARK_COLUMNS_READ, 0, 0);
+
+    thd->lex->in_update_value_clause= false;
     if (!res)
     {
       /*

sql/sql_lex.cc

 /*
-   Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+   Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -2376,7 +2376,8 @@ void Query_tables_list::destroy_query_tables_list()
 */
 
 LEX::LEX()
-  :result(0), option_type(OPT_DEFAULT), is_lex_started(0)
+  :result(0), option_type(OPT_DEFAULT), is_lex_started(0),
+  in_update_value_clause(false)
 {
 
   my_init_dynamic_array2(&plugins, sizeof(plugin_ref),

sql/sql_lex.h

-/* Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -2491,6 +2491,8 @@ struct LEX: public Query_tables_list
   
   bool escape_used;
   bool is_lex_started; /* If lex_start() did run. For debugging. */
+  /// Set to true while resolving values in ON DUPLICATE KEY UPDATE clause
+  bool in_update_value_clause;
 
   /*
     The set of those tables whose fields are referenced in all subqueries