Split item->flags into base_flags and with_flags

This was done to simplify copying of with_* flags

Other things:
- Changed Flags to C++ enums, which enables gdb to print
  out bit values for the flags. This also enables compiler
  errors if one tries to manipulate a non existing bit in
  a variable.
- Added set_maybe_null() as a shortcut as setting the
  MAYBE_NULL flags was used in a LOT of places.
- Renamed PARAM flag to SP_VAR to ensure it's not confused with persistent
  statement parameters.

36 files changed, 523 insertions, 460 deletions

diff --git a/plugin/func_test/plugin.cc b/plugin/func_test/plugin.cc
index 827c627dece..5e1f1a66fa2 100644
--- a/plugin/func_test/plugin.cc
+++ b/plugin/func_test/plugin.cc
@@ -32,7 +32,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length= MAX_FIELD_NAME * system_charset_info->mbmaxlen;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return false;
   }
   const char *func_name() const { return "sysconst_test"; }
diff --git a/plugin/type_inet/item_inetfunc.h b/plugin/type_inet/item_inetfunc.h
index 2a4605065da..f74eadb717c 100644
--- a/plugin/type_inet/item_inetfunc.h
+++ b/plugin/type_inet/item_inetfunc.h
@@ -37,7 +37,7 @@ public:
   {
     decimals= 0;
     max_length= 21;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     unsigned_flag= 1;
     return FALSE;
   }
@@ -61,7 +61,7 @@ public:
   {
     decimals= 0;
     fix_length_and_charset(3 * 8 + 7, default_charset());
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -105,7 +105,7 @@ public:
   {
     decimals= 0;
     fix_length_and_charset(16, &my_charset_bin);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -139,7 +139,7 @@ public:
     // 4 symbols per group
     fix_length_and_charset(8 * 4 + 7, default_charset());
 
-    flags|= ITEM_FLAG_MAYBE_NULL;;
+    set_maybe_null();;
     return FALSE;
   }
   String *val_str_ascii(String *to);
diff --git a/plugin/type_inet/sql_type_inet.cc b/plugin/type_inet/sql_type_inet.cc
index 58aa9ed6bde..a3e7a4d6ca1 100644
--- a/plugin/type_inet/sql_type_inet.cc
+++ b/plugin/type_inet/sql_type_inet.cc
@@ -1055,7 +1055,7 @@ public:
   {
     Type_std_attributes::operator=(Type_std_attributes_inet6());
     if (Inet6::fix_fields_maybe_null_on_conversion_to_inet6(args[0]))
-      flags|= ITEM_FLAG_MAYBE_NULL;
+      set_maybe_null();
     return false;
   }
   String *val_str(String *to) override
diff --git a/sql/item.cc b/sql/item.cc
index 8a1ac5e0a33..539ffabbe17 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -412,7 +412,8 @@ int Item::save_str_value_in_field(Field *field, String *result)
 Item::Item(THD *thd):
   name(null_clex_str), orig_name(0), is_expensive_cache(-1)
 {
-  flags= ITEM_FLAG_FIXED | ITEM_FLAG_IS_AUTOGENERATED_NAME;
+  base_flags= item_base_t::FIXED | item_base_t::IS_AUTOGENERATED_NAME;
+  with_flags= item_with_t::NONE;
   null_value= 0;
   marker= 0;
 
@@ -461,13 +462,13 @@ Item::Item(THD *thd, Item *item):
   str_value(item->str_value),
   name(item->name),
   orig_name(item->orig_name),
+  base_flags(item->base_flags & ~item_base_t::FIXED),
+  with_flags(item->with_flags),
   marker(item->marker),
   null_value(item->null_value),
   is_expensive_cache(-1),
   join_tab_idx(item->join_tab_idx)
 {
-  flags= item->flags & (item_flags_t) ~ITEM_FLAG_FIXED;
-
   next= thd->free_list;				// Put in free list
   thd->free_list= this;
 }
@@ -1587,9 +1588,10 @@ bool Item_sp_variable::fix_fields_from_item(THD *thd, Item **, const Item *it)
   max_length= it->max_length;
   decimals= it->decimals;
   unsigned_flag= it->unsigned_flag;
-  flags|= ITEM_FLAG_WITH_PARAM | ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
+  with_flags|= item_with_t::SP_VAR;
   if (thd->lex->current_select && thd->lex->current_select->master_unit()->item)
-    thd->lex->current_select->master_unit()->item->flags|= ITEM_FLAG_WITH_PARAM;
+    thd->lex->current_select->master_unit()->item->with_flags|= item_with_t::SP_VAR;
   collation.set(it->collation.collation, it->collation.derivation);
 
   return FALSE;
@@ -1711,7 +1713,7 @@ Item_splocal::Item_splocal(THD *thd,
   m_var_idx(sp_var_idx),
   m_type(handler == &type_handler_row ? ROW_ITEM : CONST_ITEM)
 {
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
 }
 
 
@@ -2074,7 +2076,7 @@ Item_name_const::Item_name_const(THD *thd, Item *name_arg, Item *val):
   StringBuffer<128> name_buffer;
   String *name_str;
 
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   if (name_item->basic_const_item() &&
       (name_str= name_item->val_str(&name_buffer))) // Can't have a NULL name
     set_name(thd, name_str);
@@ -2128,7 +2130,7 @@ bool Item_name_const::fix_fields(THD *thd, Item **ref)
   max_length= value_item->max_length;
   decimals= value_item->decimals;
   unsigned_flag= value_item->unsigned_flag;
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
@@ -2945,7 +2947,7 @@ Item_field::Item_field(THD *thd, Field *f)
   */
   orig_table_name= table_name;
   orig_field_name= field_name;
-  flags|= ITEM_FLAG_WITH_FIELD;
+  with_flags|= item_with_t::FIELD;
 }
 
 
@@ -2995,7 +2997,7 @@ Item_field::Item_field(THD *thd, Name_resolution_context *context_arg,
     name= orig_field_name;
   }
   set_field(f);
-  flags|= ITEM_FLAG_WITH_FIELD;
+  with_flags|= item_with_t::FIELD;
 }
 
 
@@ -3011,7 +3013,7 @@ Item_field::Item_field(THD *thd, Name_resolution_context *context_arg,
   collation.set(DERIVATION_IMPLICIT);
   if (select && select->parsing_place != IN_HAVING)
       select->select_n_where_fields++;
-  flags|= ITEM_FLAG_WITH_FIELD;
+  with_flags|= item_with_t::FIELD;
 }
 
 /**
@@ -3026,7 +3028,7 @@ Item_field::Item_field(THD *thd, Item_field *item)
    any_privileges(item->any_privileges)
 {
   collation.set(DERIVATION_IMPLICIT);
-  flags|= ITEM_FLAG_WITH_FIELD;
+  with_flags|= item_with_t::FIELD;
 }
 
 
@@ -3051,7 +3053,7 @@ void Item_field::set_field(Field *field_par)
   db_name= field_par->table->s->db;
   alias_name_used= field_par->table->alias_name_used;
 
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   if (field->table->s->tmp_table == SYSTEM_TMP_TABLE)
     any_privileges= 0;
 }
@@ -3958,7 +3960,7 @@ Item_param::Item_param(THD *thd, const LEX_CSTRING *name_arg,
     before mysql_stmt_execute(), so we assuming that it can be NULL until
     value is set.
   */
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
 }
 
 
@@ -3990,7 +3992,7 @@ void Item_param::sync_clones()
   {
     Item_param *c= *c_ptr;
     /* Scalar-type members: */
-    c->copy_flags(this, ITEM_FLAG_MAYBE_NULL);
+    c->copy_flags(this, item_base_t::MAYBE_NULL);
     c->null_value= null_value;
     c->Type_std_attributes::operator=(*this);
     c->Type_handler_hybrid_field_type::operator=(*this);
@@ -4042,7 +4044,7 @@ void Item_param::set_int(longlong i, uint32 max_length_arg)
   collation= DTCollation_numeric();
   max_length= max_length_arg;
   decimals= 0;
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
   DBUG_VOID_RETURN;
 }
@@ -4056,7 +4058,7 @@ void Item_param::set_double(double d)
   collation= DTCollation_numeric();
   max_length= DBL_DIG + 8;
   decimals= NOT_FIXED_DEC;
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
   DBUG_VOID_RETURN;
 }
@@ -4088,7 +4090,7 @@ void Item_param::set_decimal(const char *str, ulong length)
   max_length=
     my_decimal_precision_to_length_no_truncation(value.m_decimal.precision(),
                                                  decimals, unsigned_flag);
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
   DBUG_VOID_RETURN;
 }
@@ -4105,7 +4107,7 @@ void Item_param::set_decimal(const my_decimal *dv, bool unsigned_arg)
   unsigned_flag= unsigned_arg;
   max_length= my_decimal_precision_to_length(value.m_decimal.intg + decimals,
                                              decimals, unsigned_flag);
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
 }
 
@@ -4116,7 +4118,7 @@ void Item_param::fix_temporal(uint32 max_length_arg, uint decimals_arg)
   collation= DTCollation_numeric();
   max_length= max_length_arg;
   decimals= decimals_arg;
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
 }
 
@@ -4126,7 +4128,7 @@ void Item_param::set_time(const MYSQL_TIME *tm,
 {
   DBUG_ASSERT(value.type_handler()->cmp_type() == TIME_RESULT);
   value.time= *tm;
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
   fix_temporal(max_length_arg, decimals_arg);
 }
@@ -4161,7 +4163,7 @@ void Item_param::set_time(MYSQL_TIME *tm, timestamp_type time_type,
                                  &str, time_type, NULL, NULL, NULL);
     set_zero_time(&value.time, time_type);
   }
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
   fix_temporal(max_length_arg,
                tm->second_part > 0 ? TIME_SECOND_PART_DIGITS : 0);
@@ -4198,7 +4200,7 @@ bool Item_param::set_str(const char *str, ulong length,
   state= SHORT_DATA_VALUE;
   collation.set(tocs, DERIVATION_COERCIBLE);
   max_length= length;
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
   /* max_length and decimals are set after charset conversion */
   /* sic: str may be not null-terminated, don't add DBUG_PRINT here */
@@ -4233,7 +4235,7 @@ bool Item_param::set_longdata(const char *str, ulong length)
   if (value.m_string.append(str, length, &my_charset_bin))
     DBUG_RETURN(TRUE);
   state= LONG_DATA_VALUE;
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
 
   DBUG_RETURN(FALSE);
@@ -4334,7 +4336,7 @@ void Item_param::reset()
   value.m_string.set_charset(&my_charset_bin);
   collation.set(&my_charset_bin, DERIVATION_COERCIBLE);
   state= NO_VALUE;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   null_value= 0;
   DBUG_VOID_RETURN;
 }
@@ -4793,7 +4795,7 @@ Item_param::set_param_type_and_swap_value(Item_param *src)
   Type_std_attributes::set(src);
   set_handler(src->type_handler());
 
-  copy_flags(src, ITEM_FLAG_MAYBE_NULL);
+  copy_flags(src, item_base_t::MAYBE_NULL);
   null_value= src->null_value;
   state= src->state;
 
@@ -5613,7 +5615,7 @@ Item_field::fix_outer_field(THD *thd, Field **from_field, Item **reference)
             set_if_bigger(thd->lex->in_sum_func->max_arg_level,
                           select->nest_level);
             set_field(*from_field);
-            flags|= ITEM_FLAG_FIXED;
+            base_flags|= item_base_t::FIXED;
             mark_as_dependent(thd, last_checked_context->select_lex,
                               context->select_lex, this,
                               ((ref_type == REF_ITEM ||
@@ -6029,7 +6031,7 @@ bool Item_field::fix_fields(THD *thd, Item **reference)
     }
   }
 #endif
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   if (field->vcol_info)
     fix_session_vcol_expr_for_read(thd, field, field->vcol_info);
   if (thd->variables.sql_mode & MODE_ONLY_FULL_GROUP_BY &&
@@ -8049,20 +8051,10 @@ void Item_ref::set_properties()
     We have to remember if we refer to a sum function, to ensure that
     split_sum_func() doesn't try to change the reference.
   */
-  /* Reset flags if called from update_ref() */
-  flags&= ~ (ITEM_FLAG_WITH_SUM_FUNC |
-             ITEM_FLAG_WITH_PARAM |
-             ITEM_FLAG_WITH_WINDOW_FUNC |
-             ITEM_FLAG_WITH_SUBQUERY |
-             ITEM_FLAG_WITH_FIELD);
-
-  flags|= (ITEM_FLAG_FIXED |
-           ((*ref)->flags & (ITEM_FLAG_MAYBE_NULL |
-                             ITEM_FLAG_WITH_SUM_FUNC |
-                             ITEM_FLAG_WITH_PARAM |
-                             ITEM_FLAG_WITH_WINDOW_FUNC |
-                             ITEM_FLAG_WITH_SUBQUERY |
-                             ITEM_FLAG_WITH_FIELD)));
+  with_flags= (*ref)->with_flags;
+  base_flags|= (item_base_t::FIXED |
+                ((*ref)->base_flags & item_base_t::MAYBE_NULL));
+
   if (alias_name_used)
     return;
   if ((*ref)->type() == FIELD_ITEM)
@@ -8524,14 +8516,10 @@ Item_cache_wrapper::Item_cache_wrapper(THD *thd, Item *item_arg):
   DBUG_ASSERT(orig_item->fixed());
   Type_std_attributes::set(orig_item);
 
-  flags|= ITEM_FLAG_FIXED |
-    (orig_item->flags &
-           (ITEM_FLAG_MAYBE_NULL |
-            ITEM_FLAG_WITH_SUM_FUNC |
-            ITEM_FLAG_WITH_SUBQUERY |
-            ITEM_FLAG_WITH_PARAM |
-            ITEM_FLAG_WITH_FIELD));
-  
+  base_flags|= (item_base_t::FIXED |
+                (orig_item->base_flags & item_base_t::MAYBE_NULL));
+  with_flags|= orig_item->with_flags;
+
   name= item_arg->name;
 
   if ((expr_value= orig_item->get_cache(thd)))
@@ -8989,7 +8977,7 @@ bool Item_direct_view_ref::fix_fields(THD *thd, Item **reference)
   if (Item_direct_ref::fix_fields(thd, reference))
     return TRUE;
   if (view->table && view->table->maybe_null)
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   set_null_ref_table();
   return FALSE;
 }
@@ -9698,7 +9686,7 @@ bool Item_trigger_field::fix_fields(THD *thd, Item **items)
     field= (row_version == OLD_ROW) ? triggers->old_field[field_idx] :
                                       triggers->new_field[field_idx];
     set_field(field);
-    flags|= ITEM_FLAG_FIXED;
+    base_flags|= item_base_t::FIXED;
     return FALSE;
   }
 
diff --git a/sql/item.h b/sql/item.h
index 0c8fed43807..beda47f87fa 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -716,28 +716,94 @@ public:
 
 #define STOP_PTR ((void *) 1)
 
-/* Bits used in Item.flags */
-/* If item may be null */
-#define ITEM_FLAG_MAYBE_NULL_SHIFT 0
-#define ITEM_FLAG_MAYBE_NULL  (1<<ITEM_FLAG_MAYBE_NULL_SHIFT)
-/* If used in GROUP BY list of a query with ROLLUP */
-#define ITEM_FLAG_IN_ROLLUP       (1<<1)
-/* If Item contains an SP parameter */
-#define ITEM_FLAG_WITH_PARAM  (1<<2)
-/* If item contains a window func */
-#define ITEM_FLAG_WITH_WINDOW_FUNC (1<<3)  
-/* True if any item except Item_sum contains a field. Set during parsing. */
-#define ITEM_FLAG_WITH_FIELD (1<<4)  
-/* If item was fixed with fix_fields */
-#define ITEM_FLAG_FIXED (1<<5)
-/* Indicates that name of this Item autogenerated or set by user */
-#define ITEM_FLAG_IS_AUTOGENERATED_NAME (1 << 6)
-/* Indicates that this item is in CYCLE clause of WITH */
-#define ITEM_FLAG_IS_IN_WITH_CYCLE (1<<7)
-/* True if item contains a sum func */
-#define ITEM_FLAG_WITH_SUM_FUNC (1<< 8)
-/* True if item containts a sub query */
-#define ITEM_FLAG_WITH_SUBQUERY (1<< 9)
+
+/* Base flags (including IN) for an item */
+
+
+typedef uint8 item_flags_t;
+
+enum class item_base_t : item_flags_t
+{
+  NONE=                  0,
+#define ITEM_FLAGS_MAYBE_NULL_SHIFT 0 // Must match MAYBE_NULL
+  MAYBE_NULL=            (1<<0),   // May be NULL.
+  IN_ROLLUP=             (1<<1),   // Appears in GROUP BY list
+                                   // of a query with ROLLUP.
+  FIXED=                 (1<<2),   // Was fixed with fix_fields().
+  IS_AUTOGENERATED_NAME= (1<<3),   // The name if this Item was
+                                   // generated or set by the user.
+  IS_IN_WITH_CYCLE=      (1<<4)    // This item is in CYCLE clause
+                                   // of WITH.
+};
+
+
+/* Flags that tells us what kind of items the item contains */
+
+enum class item_with_t : item_flags_t
+{
+  NONE=             0,
+  SP_VAR=      (1<<0), // If Item contains a stored procedure variable
+  WINDOW_FUNC= (1<<1), // If item contains a window func
+  FIELD=       (1<<2), // If any item except Item_sum contains a field.
+  SUM_FUNC=    (1<<3), // If item contains a sum func
+  SUBQUERY=    (1<<4)  // If item containts a sub query
+};
+
+
+/* Make operations in item_base_t and item_with_t work like 'int' */
+static inline item_base_t operator&(const item_base_t a, const item_base_t b)
+{
+  return (item_base_t) (((item_flags_t) a) & ((item_flags_t) b));
+}
+
+static inline item_base_t & operator&=(item_base_t &a, item_base_t b)
+{
+  a= (item_base_t) (((item_flags_t) a) & (item_flags_t) b);
+  return a;
+}
+
+static inline item_base_t operator|(const item_base_t a, const item_base_t b)
+{
+  return (item_base_t) (((item_flags_t) a) | ((item_flags_t) b));
+}
+
+static inline item_base_t & operator|=(item_base_t &a, item_base_t b)
+{
+  a= (item_base_t) (((item_flags_t) a) | (item_flags_t) b);
+  return a;
+}
+
+static inline item_base_t operator~(const item_base_t a)
+{
+  return (item_base_t) ~(item_flags_t) a;
+}
+
+static inline item_with_t operator&(const item_with_t a, const item_with_t b)
+{
+  return (item_with_t) (((item_flags_t) a) & ((item_flags_t) b));
+}
+
+static inline item_with_t & operator&=(item_with_t &a, item_with_t b)
+{
+  a= (item_with_t) (((item_flags_t) a) & (item_flags_t) b);
+  return a;
+}
+
+static inline item_with_t operator|(const item_with_t a, const item_with_t b)
+{
+  return (item_with_t) (((item_flags_t) a) | ((item_flags_t) b));
+}
+
+static inline item_with_t & operator|=(item_with_t &a, item_with_t b)
+{
+  a= (item_with_t) (((item_flags_t) a) | (item_flags_t) b);
+  return a;
+}
+
+static inline item_with_t operator~(const item_with_t a)
+{
+  return (item_with_t) ~(item_flags_t) a;
+}
 
 
 class Item :public Value_source,
@@ -931,8 +997,8 @@ public:
   const char *orig_name;
 
   /* All common bool variables for an Item is stored here */
-  typedef uint16 item_flags_t;
-  item_flags_t flags;
+  item_base_t base_flags;
+  item_with_t with_flags;
 
    /* Marker is used in some functions to temporary mark an item */
   int16 marker;
@@ -957,19 +1023,40 @@ public:
   */
   uint8 join_tab_idx;
 
-  inline bool maybe_null() const { return (flags & ITEM_FLAG_MAYBE_NULL); }
-  inline bool in_rollup() const { return (flags & ITEM_FLAG_IN_ROLLUP); }
-  inline bool with_param() const { return (flags & ITEM_FLAG_WITH_PARAM); }
-  inline bool with_window_func() const { return (flags & ITEM_FLAG_WITH_WINDOW_FUNC); }
-  inline bool with_field() const { return (flags & ITEM_FLAG_WITH_FIELD); }
-  inline bool fixed() const { return (flags & ITEM_FLAG_FIXED); }
-  inline bool is_autogenerated_name() const { return (flags & ITEM_FLAG_IS_AUTOGENERATED_NAME); }
-  inline bool is_in_with_cycle() const { return (flags & ITEM_FLAG_IS_IN_WITH_CYCLE); }
-  inline bool with_sum_func() const { return (flags & ITEM_FLAG_WITH_SUM_FUNC); }
-  inline bool with_subquery() const { return (flags & ITEM_FLAG_WITH_SUBQUERY); }
-  inline void copy_flags(const Item *org, item_flags_t mask)
-  {
-    flags= (item_flags_t) ((flags & ~mask) | (org->flags & mask));
+  inline bool maybe_null() const
+  { return (bool) (base_flags & item_base_t::MAYBE_NULL); }
+  inline bool in_rollup() const
+  { return (bool) (base_flags & item_base_t::IN_ROLLUP); }
+  inline bool fixed() const
+  { return (bool) (base_flags & item_base_t::FIXED); }
+  inline bool is_autogenerated_name() const
+  { return (bool) (base_flags & item_base_t::IS_AUTOGENERATED_NAME); }
+  inline bool is_in_with_cycle() const
+  { return (bool) (base_flags & item_base_t::IS_IN_WITH_CYCLE); }
+
+  inline bool with_sp_var() const
+  { return (bool) (with_flags & item_with_t::SP_VAR); }
+  inline bool with_window_func() const
+  { return (bool) (with_flags & item_with_t::WINDOW_FUNC); }
+  inline bool with_field() const
+  { return (bool) (with_flags & item_with_t::FIELD); }
+  inline bool with_sum_func() const
+  { return (bool) (with_flags & item_with_t::SUM_FUNC); }
+  inline bool with_subquery() const
+  { return (bool) (with_flags & item_with_t::SUBQUERY); }
+  inline void copy_flags(const Item *org, item_base_t mask)
+  {
+    base_flags= (item_base_t) (((item_flags_t) base_flags &
+                                ~(item_flags_t) mask) |
+                               ((item_flags_t) org->base_flags &
+                                (item_flags_t) mask));
+  }
+  inline void copy_flags(const Item *org, item_with_t mask)
+  {
+    with_flags= (item_with_t) (((item_flags_t) with_flags &
+                                ~(item_flags_t) mask) |
+                               ((item_flags_t) org->with_flags &
+                                (item_flags_t) mask));
   }
   
   // alloc & destruct is done as start of select on THD::mem_root
@@ -1006,7 +1093,7 @@ public:
   void share_name_with(const Item *item)
   {
     name= item->name;
-    copy_flags(item, ITEM_FLAG_IS_AUTOGENERATED_NAME);
+    copy_flags(item, item_base_t::IS_AUTOGENERATED_NAME);
   }
   virtual void cleanup();
   virtual void make_send_field(THD *thd, Send_field *field);
@@ -1167,19 +1254,26 @@ public:
   {
     return type_handler()->max_display_length(this);
   }
-  const TYPELIB *get_typelib() const { return NULL; }
+  const TYPELIB *get_typelib() const override { return NULL; }
+  /* optimized setting of maybe_null without jumps. Minimizes code size */
   inline void set_maybe_null(bool maybe_null_arg)
   {
-    flags= ((item_flags_t)
-            ((flags & (item_flags_t) ~ITEM_FLAG_MAYBE_NULL) |
-             ((maybe_null_arg << ITEM_FLAG_MAYBE_NULL_SHIFT))));
+    base_flags= ((item_base_t) ((base_flags & ~item_base_t::MAYBE_NULL)) |
+                 (item_base_t) (maybe_null_arg <<
+                                ITEM_FLAGS_MAYBE_NULL_SHIFT));
+  }
+  /* This is used a lot, so make it simpler to use */
+  void set_maybe_null()
+  {
+    base_flags|= item_base_t::MAYBE_NULL;
   }
   /* This is used when calling Type_all_attributes::set_type_maybe_null() */
   void set_type_maybe_null(bool maybe_null_arg) override
   {
     set_maybe_null(maybe_null_arg);
   }
-  void set_typelib(const TYPELIB *typelib)
+
+  void set_typelib(const TYPELIB *typelib) override
   {
     // Non-field Items (e.g. hybrid functions) never have ENUM/SET types yet.
     DBUG_ASSERT(0);
@@ -1209,7 +1303,8 @@ public:
   { return NON_MONOTONIC; }
 
   /*
-    Convert "func_arg $CMP$ const" half-interval into "FUNC(func_arg) $CMP2$ const2"
+    Convert "func_arg $CMP$ const" half-interval into
+            "FUNC(func_arg) $CMP2$ const2"
 
     SYNOPSIS
       val_int_endpoint()
@@ -2713,26 +2808,28 @@ class Item_fixed_hybrid: public Item
 public:
   Item_fixed_hybrid(THD *thd): Item(thd)
   {
-    flags&= (item_flags_t) ~ITEM_FLAG_FIXED;
+    base_flags&= ~item_base_t::FIXED;
   }
   Item_fixed_hybrid(THD *thd, Item_fixed_hybrid *item)
    :Item(thd, item)
   {
-    flags|= (item_flags_t) (item->flags & ITEM_FLAG_FIXED);
+    base_flags|= (item->base_flags & item_base_t::FIXED);
   }
   bool fix_fields(THD *thd, Item **ref) override
   {
     DBUG_ASSERT(!fixed());
-    flags|= ITEM_FLAG_FIXED;
+    base_flags|= item_base_t::FIXED;
     return false;
   }
   void cleanup() override
   {
     Item::cleanup();
-    flags&= (item_flags_t) ~ITEM_FLAG_FIXED;
+    base_flags&= ~item_base_t::FIXED;
   }
-  void quick_fix_field() override { flags|= ITEM_FLAG_FIXED; }
-  void unfix_fields() override { flags&= (item_flags_t) ~ITEM_FLAG_FIXED; }
+  void quick_fix_field() override
+  { base_flags|= item_base_t::FIXED; }
+  void unfix_fields() override
+  { base_flags&= ~item_base_t::FIXED; }
 };
 
 
@@ -3641,7 +3738,7 @@ public:
   Item_null(THD *thd, const char *name_par=0, CHARSET_INFO *cs= &my_charset_bin):
     Item_basic_constant(thd)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     null_value= TRUE;
     max_length= 0;
     name.str= name_par ? name_par : "NULL";
@@ -5032,7 +5129,7 @@ public:
   Item_date_literal_for_invalid_dates(THD *thd, const Date *ltime)
    :Item_date_literal(thd, ltime)
   {
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
   }
   bool get_date(THD *thd, MYSQL_TIME *ltime, date_mode_t fuzzydate)
   {
@@ -5053,7 +5150,7 @@ public:
                                           const Datetime *ltime, uint dec_arg)
    :Item_datetime_literal(thd, ltime, dec_arg)
   {
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
   }
   bool get_date(THD *thd, MYSQL_TIME *ltime, date_mode_t fuzzydate)
   {
@@ -5965,7 +6062,7 @@ public:
     ref= &outer_ref;
     set_properties();
     /* reset flag set in set_properties() */
-    flags&= (item_flags_t) ~ITEM_FLAG_FIXED;
+    base_flags&= ~item_base_t::FIXED;
   }
   Item_outer_ref(THD *thd, Name_resolution_context *context_arg, Item **item,
                  const LEX_CSTRING &table_name_arg, LEX_CSTRING &field_name_arg,
@@ -6112,7 +6209,7 @@ protected:
     DBUG_ASSERT(org->fixed());
     item= org;
     null_value= item->maybe_null();
-    copy_flags(item, ITEM_FLAG_MAYBE_NULL);
+    copy_flags(item, item_base_t::MAYBE_NULL);
     Type_std_attributes::set(item);
     name= item->name;
     set_handler(item->type_handler());
@@ -6718,7 +6815,7 @@ public:
     value_cached(0),
     used_table_map(0)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     null_value= 1;
   }
 protected:
@@ -6729,7 +6826,7 @@ protected:
     value_cached(0),
     used_table_map(0)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     null_value= 1;
   }
 
@@ -7278,8 +7375,8 @@ public:
     Type_std_attributes::set(*attr);
     set_maybe_null(maybe_null_arg);
     copy_flags(item,
-               ITEM_FLAG_IS_AUTOGENERATED_NAME |
-               ITEM_FLAG_IS_IN_WITH_CYCLE);
+               item_base_t::IS_AUTOGENERATED_NAME |
+               item_base_t::IS_IN_WITH_CYCLE);
   }
 
   const Type_handler *type_handler() const
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 7efd76aa895..a01516cb81b 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -1142,7 +1142,7 @@ int Arg_comparator::compare_e_str_json()
 
 bool Item_func_truth::fix_length_and_dec()
 {
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value= 0;
   decimals= 0;
   max_length= 1;
@@ -1336,10 +1336,8 @@ bool Item_in_optimizer::fix_left(THD *thd)
     used_tables_cache= args[0]->used_tables();
   }
   eval_not_null_tables(NULL);
-  flags|= ((args[0]->flags &  (ITEM_FLAG_WITH_SUM_FUNC | ITEM_FLAG_WITH_PARAM |
-                              ITEM_FLAG_WITH_FIELD)) |
-           (args[1]->flags & (ITEM_FLAG_WITH_PARAM)));
-
+  with_flags|= (args[0]->with_flags |
+               (args[1]->with_flags & item_with_t::SP_VAR));
   if ((const_item_cache= args[0]->const_item()))
   {
     cache->store(args[0]);
@@ -1349,7 +1347,7 @@ bool Item_in_optimizer::fix_left(THD *thd)
   {
     /* to avoid overriding is called to update left expression */
     used_tables_and_const_cache_join(args[1]);
-    flags|= args[1]->flags & ITEM_FLAG_WITH_SUM_FUNC;
+    with_flags|= args[1]->with_flags & item_with_t::SUM_FUNC;
   }
   DBUG_RETURN(0);
 }
@@ -1371,7 +1369,7 @@ bool Item_in_optimizer::fix_fields(THD *thd, Item **ref)
   if (fix_left(thd))
     return TRUE;
   if (args[0]->maybe_null())
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
 
   if (args[1]->fix_fields_if_needed(thd, args + 1))
     return TRUE;
@@ -1383,12 +1381,11 @@ bool Item_in_optimizer::fix_fields(THD *thd, Item **ref)
     return TRUE;
   }
 
-  flags|= (ITEM_FLAG_FIXED | ITEM_FLAG_WITH_SUBQUERY |
-           (args[1]->flags & (ITEM_FLAG_MAYBE_NULL |
-                              ITEM_FLAG_WITH_SUM_FUNC |
-                              ITEM_FLAG_WITH_FIELD |
-                              ITEM_FLAG_WITH_PARAM)) |
-            (args[0]->flags & ITEM_FLAG_WITH_PARAM));
+  base_flags|= (item_base_t::FIXED |
+                (args[1]->base_flags & item_base_t::MAYBE_NULL));
+  with_flags|= (item_with_t::SUBQUERY |
+                args[1]->with_flags |
+                (args[0]->with_flags & item_with_t::SP_VAR));
   used_tables_and_const_cache_join(args[1]);
   return FALSE;
 }
@@ -1777,7 +1774,7 @@ longlong Item_func_eq::val_int()
 bool Item_func_equal::fix_length_and_dec()
 {
   bool rc= Item_bool_rowready_func2::fix_length_and_dec();
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   null_value=0;
   return rc;
 }
@@ -1931,13 +1928,11 @@ bool Item_func_interval::fix_length_and_dec()
       }
     }
   }
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   max_length= 2;
   used_tables_and_const_cache_join(row);
   not_null_tables_cache= row->not_null_tables();
-  flags|= (row->flags & (ITEM_FLAG_WITH_SUM_FUNC |
-                         ITEM_FLAG_WITH_PARAM |
-                         ITEM_FLAG_WITH_FIELD));
+  with_flags|= row->with_flags;
   return FALSE;
 }
 
@@ -2722,7 +2717,7 @@ Item_func_nullif::fix_length_and_dec()
   decimals= args[2]->decimals;
   unsigned_flag= args[2]->unsigned_flag;
   fix_char_length(args[2]->max_char_length());
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   m_arg0= args[0];
   if (setup_args_and_comparator(thd, &cmp))
     return TRUE;
@@ -3137,7 +3132,7 @@ bool Item_func_case::fix_fields(THD *thd, Item **ref)
 
   Item **pos= else_expr_addr();
   if (!pos || pos[0]->maybe_null())
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   return res;
 }
 
@@ -4898,7 +4893,7 @@ Item_cond::fix_fields(THD *thd, Item **ref)
       return TRUE; /* purecov: inspected */
     item= *li.ref(); // item can be substituted in fix_fields
     used_tables_cache|=     item->used_tables();
-    if (item->const_item() && !item->with_param() &&
+    if (item->const_item() && !item->with_sp_var() &&
         !item->is_expensive() && !cond_has_datetime_is_null(item))
     {
       if (item->eval_const_cond() == is_and_cond && top_level())
@@ -4934,17 +4929,12 @@ Item_cond::fix_fields(THD *thd, Item **ref)
 
       const_item_cache= FALSE;
     } 
-  
-    flags|= (item->flags & (ITEM_FLAG_WITH_SUM_FUNC |
-                            ITEM_FLAG_WITH_PARAM |
-                            ITEM_FLAG_WITH_FIELD |
-                            ITEM_FLAG_WITH_SUBQUERY |
-                            ITEM_FLAG_WITH_WINDOW_FUNC |
-                            ITEM_FLAG_MAYBE_NULL));
+    base_flags|= item->base_flags & item_base_t::MAYBE_NULL;
+    with_flags|= item->with_flags;
   }
   if (fix_length_and_dec())
     return TRUE;
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
@@ -4960,7 +4950,7 @@ Item_cond::eval_not_null_tables(void *opt_arg)
   while ((item=li++))
   {
     table_map tmp_table_map;
-    if (item->const_item() && !item->with_param() &&
+    if (item->const_item() && !item->with_sp_var() &&
         !item->is_expensive() && !cond_has_datetime_is_null(item))
     {
       if (item->eval_const_cond() == is_and_cond && top_level())
@@ -6086,14 +6076,14 @@ void Regexp_processor_pcre::fix_owner(Item_func *owner,
   {
     if (compile(pattern_arg, true))
     {
-      owner->flags|= ITEM_FLAG_MAYBE_NULL; // Will always return NULL
+      owner->set_maybe_null(); // Will always return NULL
       return;
     }
     set_const(true);
-    owner->flags|= subject_arg->flags & ITEM_FLAG_MAYBE_NULL;
+    owner->base_flags|= subject_arg->base_flags & item_base_t::MAYBE_NULL;
   }
   else
-    owner->flags|= ITEM_FLAG_MAYBE_NULL;
+    owner->set_maybe_null();
 }
 
 
@@ -7052,7 +7042,7 @@ bool Item_equal::fix_fields(THD *thd, Item **ref)
     not_null_tables_cache|= tmp_table_map;
     DBUG_ASSERT(!item->with_sum_func() && !item->with_subquery());
     if (item->maybe_null())
-      flags|= ITEM_FLAG_MAYBE_NULL;
+      set_maybe_null();
     if (!item->get_item_equal())
       item->set_item_equal(this);
     if (link_equal_fields && item->real_item()->type() == FIELD_ITEM)
@@ -7069,7 +7059,7 @@ bool Item_equal::fix_fields(THD *thd, Item **ref)
     last_equal_field->next_equal_field= first_equal_field;
   if (fix_length_and_dec())
     return TRUE;
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index ac4aaa09ba3..5743a6f78ee 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -368,7 +368,7 @@ public:
     Item_bool_func(thd, a, b), cache(0), expr_cache(0),
     save_cache(0), result_for_null_param(UNKNOWN)
   {
-    flags|= ITEM_FLAG_WITH_SUBQUERY;
+    with_flags|= item_with_t::SUBQUERY;
   }
   bool fix_fields(THD *, Item **) override;
   bool fix_left(THD *thd);
@@ -1130,7 +1130,7 @@ public:
         IFNULL(inet6_not_null_expr, 'foo') -> INET6 NULL
         IFNULL(inet6_not_null_expr, '::1') -> INET6 NOT NULL
     */
-    copy_flags(args[1], ITEM_FLAG_MAYBE_NULL);
+    copy_flags(args[1], item_base_t::MAYBE_NULL);
     if (Item_func_case_abbreviation2::fix_length_and_dec2(args))
       return TRUE;
     return FALSE;
@@ -2571,7 +2571,7 @@ public:
   {
     decimals=0;
     max_length=1;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     return FALSE;
   }
   bool count_sargable_conds(void *arg);
@@ -3468,7 +3468,7 @@ public:
   Item_func_cursor_found(THD *thd, const LEX_CSTRING *name, uint offset)
    :Item_func_cursor_bool_attr(thd, name, offset)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   const char *func_name() const { return "%FOUND"; }
   longlong val_int();
@@ -3483,7 +3483,7 @@ public:
   Item_func_cursor_notfound(THD *thd, const LEX_CSTRING *name, uint offset)
    :Item_func_cursor_bool_attr(thd, name, offset)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   const char *func_name() const { return "%NOTFOUND"; }
   longlong val_int();
diff --git a/sql/item_func.cc b/sql/item_func.cc
index a5538a4f2d5..b518ffec53b 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -133,12 +133,7 @@ void Item_func::sync_with_sum_func_and_with_field(List<Item> &list)
   List_iterator_fast<Item> li(list);
   Item *item;
   while ((item= li++))
-  {
-    flags|= (item->flags & (ITEM_FLAG_WITH_SUM_FUNC |
-                            ITEM_FLAG_WITH_WINDOW_FUNC |
-                            ITEM_FLAG_WITH_FIELD |
-                            ITEM_FLAG_WITH_PARAM));
-  }
+    with_flags|= item->with_flags;
 }
 
 
@@ -353,8 +348,8 @@ Item_func::fix_fields(THD *thd, Item **ref)
 	return TRUE;				/* purecov: inspected */
       item= *arg;
 
-      flags|= item->flags & ~(ITEM_FLAG_IS_AUTOGENERATED_NAME |
-                              ITEM_FLAG_IS_IN_WITH_CYCLE);
+      base_flags|= item->base_flags & item_base_t::MAYBE_NULL;
+      with_flags|= item->with_flags;
       used_tables_and_const_cache_join(item);
       not_null_tables_cache|= item->not_null_tables();
     }
@@ -363,7 +358,7 @@ Item_func::fix_fields(THD *thd, Item **ref)
     return true;
   if (fix_length_and_dec())
     return TRUE;
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
@@ -379,7 +374,7 @@ Item_func::quick_fix_field()
         (*arg)->quick_fix_field();
     }
   }
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
 }
 
 
@@ -593,9 +588,12 @@ void Item_func::split_sum_func(THD *thd,  Ref_ptr_array ref_pointer_array,
                                List<Item> &fields, uint flags)
 {
   Item **arg, **arg_end;
+  DBUG_ENTER("Item_func::split_sum_func");
+
   for (arg= args, arg_end= args+arg_count; arg != arg_end ; arg++)
     (*arg)->split_sum_func2(thd, ref_pointer_array, fields, arg,
                             flags | SPLIT_SUM_SKIP_REGISTERED);
+  DBUG_VOID_RETURN;
 }
 
 
@@ -1557,7 +1555,7 @@ bool Item_func_div::fix_length_and_dec()
   DBUG_ENTER("Item_func_div::fix_length_and_dec");
   DBUG_PRINT("info", ("name %s", func_name()));
   prec_increment= current_thd->variables.div_precincrement;
-  flags|= ITEM_FLAG_MAYBE_NULL; // division by zero
+  set_maybe_null(); // division by zero
 
   const Type_aggregator *aggregator= &type_handler_data->m_type_aggregator_for_div;
   DBUG_EXECUTE_IF("num_op", aggregator= &type_handler_data->m_type_aggregator_non_commutative_test;);
@@ -1635,7 +1633,7 @@ bool Item_func_int_div::fix_length_and_dec()
   uint32 prec= args[0]->decimal_int_part();
   set_if_smaller(prec, MY_INT64_NUM_DECIMAL_DIGITS);
   fix_char_length(prec);
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   unsigned_flag=args[0]->unsigned_flag | args[1]->unsigned_flag;
   return false;
 }
@@ -1715,7 +1713,7 @@ bool Item_func_mod::fix_length_and_dec()
 {
   DBUG_ENTER("Item_func_mod::fix_length_and_dec");
   DBUG_PRINT("info", ("name %s", func_name()));
-  flags|= ITEM_FLAG_MAYBE_NULL; // division by zero
+  set_maybe_null(); // division by zero
   const Type_aggregator *aggregator= &type_handler_data->m_type_aggregator_for_mod;
   DBUG_EXECUTE_IF("num_op", aggregator= &type_handler_data->m_type_aggregator_non_commutative_test;);
   DBUG_ASSERT(!aggregator->is_commutative());
@@ -2524,7 +2522,7 @@ void Item_func_round::fix_arg_datetime()
     return NULL.
   */
   if (!truncate)
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   fix_arg_temporal(&type_handler_datetime2, MAX_DATETIME_WIDTH);
 }
 
@@ -3205,7 +3203,7 @@ longlong Item_func_field::val_int()
 
 bool Item_func_field::fix_length_and_dec()
 {
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
   max_length=3;
   cmp_type= args[0]->result_type();
   for (uint i=1; i < arg_count ; i++)
@@ -3449,7 +3447,7 @@ udf_handler::fix_fields(THD *thd, Item_func_or_sum *func,
   args=arguments;
 
   /* Fix all arguments */
-  func->flags&= (Item::item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  func->base_flags&= ~item_base_t::MAYBE_NULL;
   func->used_tables_and_const_cache_init();
 
   if ((f_args.arg_count=arg_count))
@@ -3484,12 +3482,8 @@ udf_handler::fix_fields(THD *thd, Item_func_or_sum *func,
       */
       if (item->collation.collation->state & MY_CS_BINSORT)
 	func->collation.set(&my_charset_bin);
-      func->flags|= (item->flags & (ITEM_FLAG_MAYBE_NULL |
-                                    ITEM_FLAG_WITH_SUM_FUNC |
-                                    ITEM_FLAG_WITH_WINDOW_FUNC |
-                                    ITEM_FLAG_WITH_FIELD |
-                                    ITEM_FLAG_WITH_PARAM |
-                                    ITEM_FLAG_WITH_SUBQUERY));
+      func->base_flags|= item->base_flags & item_base_t::MAYBE_NULL;
+      func->with_flags|= item->with_flags;
       func->used_tables_and_const_cache_join(item);
       f_args.arg_type[i]=item->result_type();
     }
@@ -4759,7 +4753,7 @@ bool Item_func_set_user_var::fix_fields(THD *thd, Item **ref)
 bool
 Item_func_set_user_var::fix_length_and_dec()
 {
-  flags|= (args[0]->flags & ITEM_FLAG_MAYBE_NULL);
+  base_flags|= (args[0]->base_flags & item_base_t::MAYBE_NULL);
   decimals=args[0]->decimals;
   if (args[0]->collation.derivation == DERIVATION_NUMERIC)
   {
@@ -5616,7 +5610,7 @@ bool Item_func_get_user_var::fix_length_and_dec()
 {
   THD *thd=current_thd;
   int error;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   decimals=NOT_FIXED_DEC;
   max_length=MAX_BLOB_WIDTH;
 
@@ -5826,7 +5820,7 @@ void Item_func_get_system_var::update_null_value()
 bool Item_func_get_system_var::fix_length_and_dec()
 {
   char *cptr;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   max_length= 0;
 
   if (var->check_type(var_type))
@@ -6189,7 +6183,7 @@ bool Item_func_match::fix_fields(THD *thd, Item **ref)
 
   status_var_increment(thd->status_var.feature_fulltext);
 
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   join_key=0;
 
   /*
@@ -6525,7 +6519,7 @@ Item_func_sp::Item_func_sp(THD *thd, Name_resolution_context *context_arg,
                            sp_name *name, const Sp_handler *sph):
   Item_func(thd), Item_sp(thd, context_arg, name), m_handler(sph)
 {
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
 }
 
 
@@ -6534,7 +6528,7 @@ Item_func_sp::Item_func_sp(THD *thd, Name_resolution_context *context_arg,
                            List<Item> &list):
   Item_func(thd, list), Item_sp(thd, context_arg, name_arg), m_handler(sph)
 {
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
 }
 
 
@@ -6590,7 +6584,7 @@ bool Item_func_sp::fix_length_and_dec()
   Type_std_attributes::set(sp_result_field->type_std_attributes());
   // There is a bug in the line below. See MDEV-11292 for details.
   collation.derivation= DERIVATION_COERCIBLE;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
 
   DBUG_RETURN(FALSE);
 }
diff --git a/sql/item_func.h b/sql/item_func.h
index bc1d9ae8cc3..75d07b7fa4b 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -97,45 +97,33 @@ public:
   virtual enum Functype functype() const   { return UNKNOWN_FUNC; }
   Item_func(THD *thd): Item_func_or_sum(thd)
   {
-    flags&=(item_flags_t)  ~(ITEM_FLAG_WITH_FIELD | ITEM_FLAG_WITH_FIELD);
+    DBUG_ASSERT(with_flags == item_with_t::NONE);
+    with_flags= item_with_t::NONE;
   }
   Item_func(THD *thd, Item *a): Item_func_or_sum(thd, a)
   {
-    copy_flags(a,
-               ITEM_FLAG_WITH_SUM_FUNC | ITEM_FLAG_WITH_FIELD |
-               ITEM_FLAG_WITH_PARAM);
+    with_flags= a->with_flags;
   }
   Item_func(THD *thd, Item *a, Item *b):
     Item_func_or_sum(thd, a, b)
   {
-    flags|= ((a->flags | b->flags) &
-             (ITEM_FLAG_WITH_SUM_FUNC |
-              ITEM_FLAG_WITH_PARAM |
-              ITEM_FLAG_WITH_FIELD));
+    with_flags= a->with_flags | b->with_flags;
   }
   Item_func(THD *thd, Item *a, Item *b, Item *c):
     Item_func_or_sum(thd, a, b, c)
   {
-    flags|= ((a->flags | b->flags | c->flags) &
-             (ITEM_FLAG_WITH_SUM_FUNC |
-              ITEM_FLAG_WITH_PARAM |
-              ITEM_FLAG_WITH_FIELD));
+    with_flags|= a->with_flags | b->with_flags | c->with_flags;
   }
   Item_func(THD *thd, Item *a, Item *b, Item *c, Item *d):
     Item_func_or_sum(thd, a, b, c, d)
   {
-    flags|= ((a->flags | b->flags | c->flags | d->flags) &
-             (ITEM_FLAG_WITH_SUM_FUNC |
-              ITEM_FLAG_WITH_PARAM |
-              ITEM_FLAG_WITH_FIELD));
+    with_flags= a->with_flags | b->with_flags | c->with_flags | d->with_flags;
   }
   Item_func(THD *thd, Item *a, Item *b, Item *c, Item *d, Item* e):
     Item_func_or_sum(thd, a, b, c, d, e)
   {
-    flags|= ((a->flags | b->flags | c->flags | d->flags | e->flags) &
-             (ITEM_FLAG_WITH_SUM_FUNC |
-              ITEM_FLAG_WITH_PARAM |
-              ITEM_FLAG_WITH_FIELD));
+    with_flags= (a->with_flags | b->with_flags | c->with_flags | d->with_flags |
+                 e->with_flags);
   }
   Item_func(THD *thd, List<Item> &list):
     Item_func_or_sum(thd, list)
@@ -153,10 +141,11 @@ public:
     Item_func_or_sum::cleanup();
     used_tables_and_const_cache_init();
   }
-  void fix_after_pullout(st_select_lex *new_parent, Item **ref, bool merge);
-  void quick_fix_field();
-  table_map not_null_tables() const;
-  void update_used_tables()
+  void fix_after_pullout(st_select_lex *new_parent, Item **ref, bool merge)
+    override;
+  void quick_fix_field() override;
+  table_map not_null_tables() const override;
+  void update_used_tables() override
   {
     used_tables_and_const_cache_init();
     used_tables_and_const_cache_update_and_join(arg_count, args);
@@ -201,7 +190,7 @@ public:
     if (max_result_length >= MAX_BLOB_WIDTH)
     {
       max_length= MAX_BLOB_WIDTH;
-      flags|= ITEM_FLAG_MAYBE_NULL;
+      set_maybe_null();
     }
     else
       max_length= (uint32) max_result_length;
@@ -1253,7 +1242,7 @@ public:
   Item_func_cursor_rowcount(THD *thd, const LEX_CSTRING *name, uint offset)
    :Item_longlong_func(thd), Cursor_ref(name, offset)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   const char *func_name() const { return "%ROWCOUNT"; }
   longlong val_int();
@@ -1432,7 +1421,7 @@ public:
   void print(String *str, enum_query_type query_type);
   void fix_length_and_dec_generic()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
 };
 
@@ -1697,7 +1686,7 @@ class Item_dec_func :public Item_real_func
   {
     decimals= NOT_FIXED_DEC;
     max_length= float_length(decimals);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
 };
@@ -1871,7 +1860,7 @@ public:
     fix_attributes_datetime(0);
     set_handler(&type_handler_datetime2);
     // Thinks like CEILING(TIMESTAMP'0000-01-01 23:59:59.9') returns NULL
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   bool fix_length_and_dec();
   String *str_op(String *str) { DBUG_ASSERT(0); return 0; }
@@ -2232,7 +2221,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length=10;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     return FALSE;
   }
   bool eval_not_null_tables(void *)
@@ -2495,7 +2484,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length=1;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     return FALSE;
   }
   virtual void print(String *str, enum_query_type query_type);
@@ -2577,7 +2566,7 @@ public:
     DBUG_ASSERT(fixed() == 0);
     bool res= udf.fix_fields(thd, this, arg_count, args);
     set_non_deterministic_if_needed();
-    flags|= ITEM_FLAG_FIXED;
+    base_flags|= item_base_t::FIXED;
     return res;
   }
   void fix_num_length_and_dec();
@@ -2826,7 +2815,8 @@ public:
     { DBUG_ASSERT(fixed()); null_value=1; return 0; }
   double val_real() { DBUG_ASSERT(fixed()); null_value= 1; return 0.0; }
   longlong val_int() { DBUG_ASSERT(fixed()); null_value=1; return 0; }
-  bool fix_length_and_dec() { flags|= ITEM_FLAG_MAYBE_NULL; max_length=0; return FALSE; }
+  bool fix_length_and_dec() override
+  { base_flags|= item_base_t::MAYBE_NULL; max_length=0; return FALSE; }
 };
 
 #endif /* HAVE_DLOPEN */
@@ -2869,7 +2859,7 @@ class Item_func_get_lock final :public Item_func_lock
   bool fix_length_and_dec()
   {
     max_length= 1;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd) final
@@ -2901,7 +2891,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length= 1;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd) final
@@ -2934,7 +2924,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length=21;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_vcol_func_processor(void *arg)
@@ -3376,7 +3366,7 @@ public:
   {
     decimals=0;
     max_length=1;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_vcol_func_processor(void *arg)
@@ -3399,7 +3389,7 @@ public:
   bool fix_length_and_dec()
   {
     decimals=0; max_length=10;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_vcol_func_processor(void *arg)
@@ -3456,7 +3446,7 @@ public:
   bool fix_length_and_dec()
   {
     decimals= 0;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     return FALSE;
   }
   bool check_vcol_func_processor(void *arg)
@@ -3626,7 +3616,7 @@ public:
   bool fix_length_and_dec()
   {
     decimals= 0;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     return FALSE;
   }
   bool check_vcol_func_processor(void *arg)
@@ -3673,7 +3663,7 @@ public:
   }
   bool fix_length_and_dec()
   {
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     null_value= false;
     max_length= 11;
     return FALSE;
@@ -3733,7 +3723,7 @@ public:
   void update_used_tables()
   {
     Item_func::update_used_tables();
-    copy_flags(last_value, ITEM_FLAG_MAYBE_NULL);
+    copy_flags(last_value, item_base_t::MAYBE_NULL);
   }
   Item *get_copy(THD *thd)
   { return get_item_copy<Item_func_last_value>(thd, this); }
@@ -3756,7 +3746,7 @@ public:
   {
     unsigned_flag= 0;
     max_length= MAX_BIGINT_WIDTH;
-    flags|= ITEM_FLAG_MAYBE_NULL;             /* In case of errors */
+    set_maybe_null();             /* In case of errors */
     return FALSE;
   }
   /*
diff --git a/sql/item_geofunc.cc b/sql/item_geofunc.cc
index e6a522a0d85..0edc9a8e08a 100644
--- a/sql/item_geofunc.cc
+++ b/sql/item_geofunc.cc
@@ -47,7 +47,7 @@ bool Item_geometry_func::fix_length_and_dec()
   collation.set(&my_charset_bin);
   decimals=0;
   max_length= (uint32) UINT_MAX32;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -221,7 +221,7 @@ bool Item_func_as_wkt::fix_length_and_dec()
 {
   collation.set(default_charset(), DERIVATION_COERCIBLE, MY_REPERTOIRE_ASCII);
   max_length= (uint32) UINT_MAX32;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -248,7 +248,7 @@ bool Item_func_as_geojson::fix_length_and_dec()
 {
   collation.set(default_charset(), DERIVATION_COERCIBLE, MY_REPERTOIRE_ASCII);
   max_length=MAX_BLOB_WIDTH;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
diff --git a/sql/item_geofunc.h b/sql/item_geofunc.h
index aba255df349..2ead0a884fe 100644
--- a/sql/item_geofunc.h
+++ b/sql/item_geofunc.h
@@ -284,7 +284,7 @@ public:
     collation.set(&my_charset_bin);
     decimals=0;
     max_length= (uint32) UINT_MAX32;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -326,7 +326,7 @@ public:
   {
     // "GeometryCollection" is the longest
     fix_length_and_charset(20, default_charset());
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   };
   Item *get_copy(THD *thd)
@@ -675,7 +675,7 @@ public:
   Item_func_spatial_rel(THD *thd, Item *a, Item *b, enum Functype sp_rel):
     Item_bool_func2_with_rev(thd, a, b), spatial_rel(sp_rel)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   enum Functype functype() const { return spatial_rel; }
   enum Functype rev_functype() const
@@ -854,11 +854,12 @@ class Item_func_isempty: public Item_bool_func_args_geometry
 public:
   Item_func_isempty(THD *thd, Item *a)
    :Item_bool_func_args_geometry(thd, a) {}
-  longlong val_int();
+  longlong val_int() override;
   const char *func_name() const { return "st_isempty"; }
-  bool fix_length_and_dec() { flags|= ITEM_FLAG_MAYBE_NULL; return FALSE; }
-  bool need_parentheses_in_default() { return false; }
-  Item *get_copy(THD *thd)
+  bool fix_length_and_dec() override
+  { set_maybe_null(); return FALSE; }
+  bool need_parentheses_in_default() override { return false; }
+  Item *get_copy(THD *thd) override
   { return get_item_copy<Item_func_isempty>(thd, this); }
 };
 
@@ -907,10 +908,11 @@ class Item_func_dimension: public Item_long_func_args_geometry
 public:
   Item_func_dimension(THD *thd, Item *a)
    :Item_long_func_args_geometry(thd, a) {}
-  longlong val_int();
+  longlong val_int() override;
   const char *func_name() const { return "st_dimension"; }
-  bool fix_length_and_dec() { max_length= 10; flags|= ITEM_FLAG_MAYBE_NULL; return FALSE; }
-  Item *get_copy(THD *thd)
+  bool fix_length_and_dec() override
+  { max_length= 10; set_maybe_null(); return FALSE; }
+  Item *get_copy(THD *thd) override
   { return get_item_copy<Item_func_dimension>(thd, this); }
 };
 
@@ -925,7 +927,7 @@ public:
   {
     if (Item_real_func::fix_length_and_dec())
       return TRUE;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -943,7 +945,7 @@ public:
   {
     if (Item_real_func::fix_length_and_dec())
       return TRUE;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -956,10 +958,11 @@ class Item_func_numgeometries: public Item_long_func_args_geometry
 public:
   Item_func_numgeometries(THD *thd, Item *a)
    :Item_long_func_args_geometry(thd, a) {}
-  longlong val_int();
+  longlong val_int() override;
   const char *func_name() const { return "st_numgeometries"; }
-  bool fix_length_and_dec() { max_length= 10; flags|= ITEM_FLAG_MAYBE_NULL; return FALSE; }
-  Item *get_copy(THD *thd)
+  bool fix_length_and_dec() override
+  { max_length= 10; set_maybe_null(); return FALSE; }
+  Item *get_copy(THD *thd) override
   { return get_item_copy<Item_func_numgeometries>(thd, this); }
 };
 
@@ -969,10 +972,11 @@ class Item_func_numinteriorring: public Item_long_func_args_geometry
 public:
   Item_func_numinteriorring(THD *thd, Item *a)
    :Item_long_func_args_geometry(thd, a) {}
-  longlong val_int();
+  longlong val_int() override;
   const char *func_name() const { return "st_numinteriorrings"; }
-  bool fix_length_and_dec() { max_length= 10; flags|= ITEM_FLAG_MAYBE_NULL; return FALSE; }
-  Item *get_copy(THD *thd)
+  bool fix_length_and_dec() override
+  { max_length= 10; set_maybe_null(); return FALSE; }
+  Item *get_copy(THD *thd) override
   { return get_item_copy<Item_func_numinteriorring>(thd, this); }
 };
 
@@ -982,10 +986,11 @@ class Item_func_numpoints: public Item_long_func_args_geometry
 public:
   Item_func_numpoints(THD *thd, Item *a)
    :Item_long_func_args_geometry(thd, a) {}
-  longlong val_int();
+  longlong val_int() override;
   const char *func_name() const { return "st_numpoints"; }
-  bool fix_length_and_dec() { max_length= 10; flags|= ITEM_FLAG_MAYBE_NULL; return FALSE; }
-  Item *get_copy(THD *thd)
+  bool fix_length_and_dec() override
+  { max_length= 10; set_maybe_null(); return FALSE; }
+  Item *get_copy(THD *thd) override
   { return get_item_copy<Item_func_numpoints>(thd, this); }
 };
 
@@ -1000,7 +1005,7 @@ public:
   {
     if (Item_real_func::fix_length_and_dec())
       return TRUE;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -1020,7 +1025,7 @@ public:
   {
     if (Item_real_func::fix_length_and_dec())
       return TRUE;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -1033,10 +1038,11 @@ class Item_func_srid: public Item_long_func_args_geometry
 public:
   Item_func_srid(THD *thd, Item *a)
    :Item_long_func_args_geometry(thd, a) {}
-  longlong val_int();
+  longlong val_int() override;
   const char *func_name() const { return "srid"; }
-  bool fix_length_and_dec() { max_length= 10; flags|= ITEM_FLAG_MAYBE_NULL; return FALSE; }
-  Item *get_copy(THD *thd)
+  bool fix_length_and_dec() override
+  { max_length= 10; set_maybe_null(); return FALSE; }
+  Item *get_copy(THD *thd) override
   { return get_item_copy<Item_func_srid>(thd, this); }
 };
 
diff --git a/sql/item_jsonfunc.cc b/sql/item_jsonfunc.cc
index f0dc8acab30..0788c374475 100644
--- a/sql/item_jsonfunc.cc
+++ b/sql/item_jsonfunc.cc
@@ -386,7 +386,7 @@ bool Item_func_json_exists::fix_length_and_dec()
 {
   if (Item_bool_func::fix_length_and_dec())
     return TRUE;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   path.set_constant_flag(args[1]->const_item());
   return FALSE;
 }
@@ -440,7 +440,7 @@ bool Item_func_json_value::fix_length_and_dec()
   collation.set(args[0]->collation);
   max_length= args[0]->max_length;
   set_constant_flag(args[1]->const_item());
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -450,7 +450,7 @@ bool Item_func_json_query::fix_length_and_dec()
   collation.set(args[0]->collation);
   max_length= args[0]->max_length;
   set_constant_flag(args[1]->const_item());
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -598,7 +598,7 @@ bool Item_func_json_unquote::fix_length_and_dec()
   collation.set(&my_charset_utf8mb3_general_ci,
                 DERIVATION_COERCIBLE, MY_REPERTOIRE_ASCII);
   max_length= args[0]->max_length;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -721,7 +721,7 @@ bool Item_func_json_extract::fix_length_and_dec()
   max_length= args[0]->max_length * (arg_count - 1);
 
   mark_constant_paths(paths, args+1, arg_count-1);
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -990,7 +990,7 @@ bool Item_func_json_contains::fix_length_and_dec()
 {
   a2_constant= args[1]->const_item();
   a2_parsed= FALSE;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   if (arg_count > 2)
     path.set_constant_flag(args[2]->const_item());
   return Item_bool_func::fix_length_and_dec();
@@ -1241,7 +1241,7 @@ bool Item_func_json_contains_path::fix_length_and_dec()
 {
   ooa_constant= args[1]->const_item();
   ooa_parsed= FALSE;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   mark_constant_paths(paths, args+2, arg_count-2);
   return Item_bool_func::fix_length_and_dec();
 }
@@ -1632,7 +1632,7 @@ bool Item_func_json_array_append::fix_length_and_dec()
   }
 
   fix_char_length_ulonglong(char_length);
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -2551,7 +2551,7 @@ bool Item_func_json_length::fix_length_and_dec()
 {
   if (arg_count > 1)
     path.set_constant_flag(args[1]->const_item());
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   max_length= 10;
   return FALSE;
 }
@@ -2697,7 +2697,7 @@ bool Item_func_json_type::fix_length_and_dec()
 {
   collation.set(&my_charset_utf8mb3_general_ci);
   max_length= 12;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -2766,7 +2766,7 @@ bool Item_func_json_insert::fix_length_and_dec()
   }
 
   fix_char_length_ulonglong(char_length);
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -3018,7 +3018,7 @@ bool Item_func_json_remove::fix_length_and_dec()
   max_length= args[0]->max_length;
 
   mark_constant_paths(paths, args+1, arg_count-1);
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -3203,7 +3203,7 @@ bool Item_func_json_keys::fix_length_and_dec()
 {
   collation.set(args[0]->collation);
   max_length= args[0]->max_length;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   if (arg_count > 1)
     path.set_constant_flag(args[1]->const_item());
   return FALSE;
@@ -3388,7 +3388,7 @@ bool Item_func_json_search::fix_length_and_dec()
 
   if (arg_count > 4)
     mark_constant_paths(paths, args+4, arg_count-4);
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -3571,7 +3571,7 @@ bool Item_func_json_format::fix_length_and_dec()
 {
   decimals= 0;
   max_length= args[0]->max_length;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -3779,7 +3779,7 @@ Item_func_json_objectagg::fix_fields(THD *thd, Item **ref)
   if (init_sum_func_check(thd))
     return TRUE;
 
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
 
   /*
     Fix fields for select list and ORDER clause
@@ -3789,9 +3789,7 @@ Item_func_json_objectagg::fix_fields(THD *thd, Item **ref)
   {
     if (args[i]->fix_fields_if_needed_for_scalar(thd, &args[i]))
       return TRUE;
-    flags|= (args[i]->flags & (ITEM_FLAG_WITH_SUBQUERY |
-                               ITEM_FLAG_WITH_PARAM |
-                               ITEM_FLAG_WITH_WINDOW_FUNC));
+    with_flags|= args[i]->with_flags;
   }
 
   /* skip charset aggregation for order columns */
@@ -3808,7 +3806,7 @@ Item_func_json_objectagg::fix_fields(THD *thd, Item **ref)
   if (check_sum_func(thd, ref))
     return TRUE;
 
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
diff --git a/sql/item_jsonfunc.h b/sql/item_jsonfunc.h
index 724f45a9d62..11b3db4f952 100644
--- a/sql/item_jsonfunc.h
+++ b/sql/item_jsonfunc.h
@@ -81,7 +81,7 @@ public:
   {
     if (Item_bool_func::fix_length_and_dec())
       return TRUE;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool set_format_by_check_constraint(Send_field_extended_metadata *to) const
diff --git a/sql/item_row.cc b/sql/item_row.cc
index 5cbd2d4caa9..3981392b0ae 100644
--- a/sql/item_row.cc
+++ b/sql/item_row.cc
@@ -38,7 +38,7 @@ bool Item_row::fix_fields(THD *thd, Item **ref)
 {
   DBUG_ASSERT(fixed() == 0);
   null_value= 0;
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+  base_flags&= ~item_base_t::MAYBE_NULL;
 
   Item **arg, **arg_end;
   for (arg= args, arg_end= args + arg_count; arg != arg_end ; arg++)
@@ -61,14 +61,10 @@ bool Item_row::fix_fields(THD *thd, Item **ref)
           with_null|= 1;
       }
     }
-    flags|= (item->flags & (ITEM_FLAG_MAYBE_NULL |
-                            ITEM_FLAG_WITH_SUM_FUNC |
-                            ITEM_FLAG_WITH_WINDOW_FUNC |
-                            ITEM_FLAG_WITH_FIELD |
-                            ITEM_FLAG_WITH_SUBQUERY |
-                            ITEM_FLAG_WITH_PARAM));
+    base_flags|= (item->base_flags & item_base_t::MAYBE_NULL);
+    with_flags|= item->with_flags;
   }
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index ff6c221c9cb..5c0cf872a9b 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -124,7 +124,8 @@ bool Item_str_func::fix_fields(THD *thd, Item **ref)
     In Item_str_func::check_well_formed_result() we may set null_value
     flag on the same condition as in test() below.
   */
-  flags|= thd->is_strict_mode() ? ITEM_FLAG_MAYBE_NULL : 0;
+  if (thd->is_strict_mode())
+    set_maybe_null();
   return res;
 }
 
@@ -286,7 +287,7 @@ String *Item_func_sha2::val_str_ascii(String *str)
 
 bool Item_func_sha2::fix_length_and_dec()
 {
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   max_length = 0;
 
   int sha_variant= (int)(args[1]->const_item() ? args[1]->val_int() : 512);
@@ -374,7 +375,7 @@ bool Item_func_aes_encrypt::fix_length_and_dec()
 bool Item_func_aes_decrypt::fix_length_and_dec()
 {
   max_length=args[0]->max_length;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   what= ENCRYPTION_FLAG_DECRYPT;
   return FALSE;
 }
@@ -382,11 +383,11 @@ bool Item_func_aes_decrypt::fix_length_and_dec()
 
 bool Item_func_to_base64::fix_length_and_dec()
 {
-  flags|= args[0]->flags & ITEM_FLAG_MAYBE_NULL;
+  base_flags|= args[0]->base_flags & item_base_t::MAYBE_NULL;
   collation.set(default_charset(), DERIVATION_COERCIBLE, MY_REPERTOIRE_ASCII);
   if (args[0]->max_length > (uint) my_base64_encode_max_arg_length())
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     fix_char_length_ulonglong((ulonglong) my_base64_encode_max_arg_length());
   }
   else
@@ -442,7 +443,8 @@ bool Item_func_from_base64::fix_length_and_dec()
     int length= my_base64_needed_decoded_length((int) args[0]->max_length);
     fix_char_length_ulonglong((ulonglong) length);
   }
-  flags|= ITEM_FLAG_MAYBE_NULL; // Can be NULL, e.g. in case of badly formed input string
+  // Can be NULL, e.g. in case of badly formed input string
+  set_maybe_null();
   return FALSE;
 }
 
@@ -2310,7 +2312,8 @@ bool Item_func_encode::seed()
 bool Item_func_encode::fix_length_and_dec()
 {
   max_length=args[0]->max_length;
-  flags|= (args[0]->flags | args[1]->flags) & ITEM_FLAG_MAYBE_NULL;
+  base_flags|= ((args[0]->base_flags | args[1]->base_flags) &
+                item_base_t::MAYBE_NULL);
   collation.set(&my_charset_bin);
   /* Precompute the seed state if the item is constant. */
   seeded= args[1]->const_item() &&
@@ -2474,11 +2477,11 @@ bool Item_func_current_role::fix_fields(THD *thd, Item **ref)
       return 1;
     str_value.mark_as_const();
     null_value= 0;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     return 0;
   }
   null_value= 1;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return 0;
 }
 
@@ -2813,7 +2816,7 @@ bool Item_func_elt::fix_length_and_dec()
     set_if_bigger(decimals,args[i]->decimals);
   }
   fix_char_length(char_length);
-  flags|= ITEM_FLAG_MAYBE_NULL;					// NULL if wrong first arg
+  set_maybe_null(); // NULL if wrong first arg
   return FALSE;
 }
 
@@ -3037,7 +3040,7 @@ bool Item_func_repeat::fix_length_and_dec()
     return false;
   }
   max_length= MAX_BLOB_WIDTH;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return false;
 }
 
@@ -3109,7 +3112,7 @@ bool Item_func_space::fix_length_and_dec()
     return false;
   }
   max_length= MAX_BLOB_WIDTH;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return false;
 }
 
@@ -3164,7 +3167,7 @@ bool Item_func_binlog_gtid_pos::fix_length_and_dec()
 {
   collation.set(system_charset_info);
   max_length= MAX_BLOB_WIDTH;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -3206,8 +3209,9 @@ bool Item_func_pad::fix_length_and_dec()
   if (arg_count == 3)
   {
     String *str;
-    if (!args[2]->basic_const_item() || !(str= args[2]->val_str(&pad_str)) || !str->length())
-      flags|= ITEM_FLAG_MAYBE_NULL;
+    if (!args[2]->basic_const_item() || !(str= args[2]->val_str(&pad_str)) ||
+        !str->length())
+      set_maybe_null();
     // Handle character set for args[0] and args[2].
     if (agg_arg_charsets_for_string_result(collation, &args[0], 2, 2))
       return TRUE;
@@ -3228,7 +3232,7 @@ bool Item_func_pad::fix_length_and_dec()
     return false;
   }
   max_length= MAX_BLOB_WIDTH;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return false;
 }
 
@@ -3613,7 +3617,7 @@ bool Item_func_weight_string::fix_length_and_dec()
                  args[0]->max_char_length() : nweights * cs->levels_for_order;
     max_length= (uint32) cs->strnxfrmlen(char_length * cs->mbmaxlen);
   }
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -4397,7 +4401,7 @@ bool Item_func_dyncol_create::fix_fields(THD *thd, Item **ref)
 bool Item_func_dyncol_create::fix_length_and_dec()
 {
   max_length= MAX_BLOB_WIDTH;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   collation.set(&my_charset_bin);
   decimals= 0;
   return FALSE;
diff --git a/sql/item_strfunc.h b/sql/item_strfunc.h
index 71d63ff9939..71701be3837 100644
--- a/sql/item_strfunc.h
+++ b/sql/item_strfunc.h
@@ -294,7 +294,7 @@ public:
   {
     collation.set(system_charset_info);
     max_length= MAX_BLOB_WIDTH;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   const char *func_name() const { return "decode_histogram"; }
@@ -506,7 +506,7 @@ public:
   bool fix_length_and_dec()
   {
     bool res= Item_func_substr::fix_length_and_dec();
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return res;
   }
   const char *func_name() const { return "substr_oracle"; }
@@ -581,7 +581,7 @@ public:
   bool fix_length_and_dec()
   {
     bool res= Item_func_trim::fix_length_and_dec();
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return res;
   }
   Item *get_copy(THD *thd)
@@ -620,7 +620,7 @@ public:
   bool fix_length_and_dec()
   {
     bool res= Item_func_ltrim::fix_length_and_dec();
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return res;
   }
   Item *get_copy(THD *thd)
@@ -655,7 +655,7 @@ public:
   bool fix_length_and_dec()
   {
     bool res= Item_func_rtrim::fix_length_and_dec();
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return res;
   }
   Item *get_copy(THD *thd)
@@ -714,7 +714,7 @@ public:
   String *val_str(String *);
   bool fix_length_and_dec()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     /* 9 = MAX ((8- (arg_len % 8)) + 1) */
     max_length = args[0]->max_length + 9;
     return FALSE;
@@ -735,7 +735,7 @@ public:
   String *val_str(String *);
   bool fix_length_and_dec()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     /* 9 = MAX ((8- (arg_len % 8)) + 1) */
     max_length= args[0]->max_length;
     if (max_length >= 9U)
@@ -775,7 +775,7 @@ public:
   String *val_str(String *);
   bool fix_length_and_dec()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     max_length = 13;
     return FALSE;
   }
@@ -855,7 +855,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length= MAX_FIELD_NAME * system_charset_info->mbmaxlen;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   const char *func_name() const { return "database"; }
@@ -880,7 +880,7 @@ public:
   {
     max_length= 512 * system_charset_info->mbmaxlen;
     null_value= false;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -1155,7 +1155,7 @@ public:
   bool fix_length_and_dec()
   {
     bool res= Item_func_rpad::fix_length_and_dec();
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return res;
   }
   const char *func_name() const { return "rpad_oracle"; }
@@ -1190,7 +1190,7 @@ public:
   bool fix_length_and_dec()
   {
     bool res= Item_func_lpad::fix_length_and_dec();
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return res;
   }
   const char *func_name() const { return "lpad_oracle"; }
@@ -1210,7 +1210,7 @@ public:
   {
     collation.set(default_charset());
     fix_char_length(64);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -1260,7 +1260,7 @@ public:
   Item_func_unhex(THD *thd, Item *a): Item_str_func(thd, a)
   {
     /* there can be bad hex strings */
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   const char *func_name() const { return "unhex"; }
   String *val_str(String *);
@@ -1287,7 +1287,7 @@ public:
   Item_func_like_range(THD *thd, Item *a, Item *b, bool is_min_arg):
     Item_str_func(thd, a, b), is_min(is_min_arg)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   String *val_str(String *);
   bool fix_length_and_dec()
@@ -1360,7 +1360,7 @@ public:
   bool fix_length_and_dec()
   {
     collation.set(&my_charset_bin, DERIVATION_COERCIBLE);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     max_length=MAX_BLOB_WIDTH;
     return FALSE;
   }
@@ -1534,7 +1534,7 @@ public:
   {
      collation.set(system_charset_info);
      max_length= 64 * collation.collation->mbmaxlen; // should be enough
-     flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+     base_flags&= ~item_base_t::MAYBE_NULL;
      return FALSE;
   };
   table_map not_null_tables() const { return 0; }
@@ -1627,7 +1627,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length=10;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE; }
   longlong val_int();
   Item *get_copy(THD *thd)
@@ -1665,7 +1665,7 @@ public:
    :Item_str_binary_checksum_func(thd, a) {}
   bool fix_length_and_dec()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     max_length= MAX_BLOB_WIDTH;
     return FALSE;
   }
@@ -1745,7 +1745,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length= MAX_BLOB_WIDTH;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     decimals= 0;
     return FALSE;
   }
@@ -1764,7 +1764,7 @@ public:
   {}
   bool fix_length_and_dec()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     max_length= MAX_BLOB_WIDTH;
     return FALSE;
   }
@@ -1807,7 +1807,7 @@ public:
     {collation.set(DYNCOL_UTF);}
   bool fix_length_and_dec()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     max_length= MAX_BLOB_WIDTH;
     return FALSE;
   }
@@ -1851,7 +1851,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length= WSREP_GTID_STR_LEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
@@ -1868,7 +1868,7 @@ public:
   bool fix_length_and_dec()
   {
     max_length= WSREP_GTID_STR_LEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   Item *get_copy(THD *thd)
diff --git a/sql/item_subselect.cc b/sql/item_subselect.cc
index 1e2c3591918..581427c34eb 100644
--- a/sql/item_subselect.cc
+++ b/sql/item_subselect.cc
@@ -67,7 +67,7 @@ Item_subselect::Item_subselect(THD *thd_arg):
 #ifndef DBUG_OFF
   exec_counter= 0;
 #endif
-  flags|= ITEM_FLAG_WITH_SUBQUERY;
+  with_flags|= item_with_t::SUBQUERY;
   reset();
   /*
     Item value is NULL if select_result_interceptor didn't change this value
@@ -342,7 +342,7 @@ bool Item_subselect::fix_fields(THD *thd_param, Item **ref)
     if (uncacheable & UNCACHEABLE_RAND)
       used_tables_cache|= RAND_TABLE_BIT;
   }
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
 
 end:
   done_first_fix_fields= FALSE;
@@ -1052,7 +1052,7 @@ Item_singlerow_subselect::Item_singlerow_subselect(THD *thd, st_select_lex *sele
 {
   DBUG_ENTER("Item_singlerow_subselect::Item_singlerow_subselect");
   init(select_lex, new (thd->mem_root) select_singlerow_subselect(thd, this));
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   max_columns= UINT_MAX;
   DBUG_VOID_RETURN;
 }
@@ -1089,7 +1089,7 @@ Item_maxmin_subselect::Item_maxmin_subselect(THD *thd,
        new (thd->mem_root) select_max_min_finder_subselect(thd,
              this, max_arg, parent->substype() == Item_subselect::ALL_SUBS));
   max_columns= 1;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   max_columns= 1;
 
   /*
@@ -1277,7 +1277,7 @@ bool Item_singlerow_subselect::fix_length_and_dec()
   else
   {
     for (uint i= 0; i < max_columns; i++)
-      row[i]->flags|= ITEM_FLAG_MAYBE_NULL;
+      row[i]->set_maybe_null();
   }
   return FALSE;
 }
@@ -1489,7 +1489,7 @@ Item_exists_subselect::Item_exists_subselect(THD *thd,
   init(select_lex, new (thd->mem_root) select_exists_subselect(thd, this));
   max_columns= UINT_MAX;
   null_value= FALSE; //can't be NULL
-  flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL; //can't be NULL
+  base_flags&= ~item_base_t::MAYBE_NULL; //can't be NULL
   value= 0;
   DBUG_VOID_RETURN;
 }
@@ -1538,7 +1538,7 @@ Item_in_subselect::Item_in_subselect(THD *thd, Item * left_exp,
   func= &eq_creator;
   init(select_lex, new (thd->mem_root) select_exists_subselect(thd, this));
   max_columns= UINT_MAX;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   reset();
   //if test_limit will fail then error will be reported to client
   test_limit(select_lex->master_unit());
@@ -3441,7 +3441,7 @@ bool Item_in_subselect::fix_fields(THD *thd_arg, Item **ref)
   else
   if (Item_subselect::fix_fields(thd_arg, ref))
     goto err;
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   thd->where= save_where;
   DBUG_RETURN(FALSE);
 
diff --git a/sql/item_sum.cc b/sql/item_sum.cc
index 1c52611e280..64106e4e516 100644
--- a/sql/item_sum.cc
+++ b/sql/item_sum.cc
@@ -407,7 +407,7 @@ bool Item_sum::register_sum_func(THD *thd, Item **ref)
     for (sl= thd->lex->current_select; 
          sl && sl != aggr_sel && sl->master_unit()->item;
          sl= sl->master_unit()->outer_select() )
-      sl->master_unit()->item->flags|= ITEM_FLAG_WITH_SUM_FUNC;
+      sl->master_unit()->item->with_flags|= item_with_t::SUM_FUNC;
   }
   thd->lex->current_select->mark_as_dependent(thd, aggr_sel, NULL);
 
@@ -488,7 +488,7 @@ void Item_sum::mark_as_sum_func()
   cur_select->n_sum_items++;
   cur_select->with_sum_func= 1;
   const_item_cache= false;
-  flags= (flags | ITEM_FLAG_WITH_SUM_FUNC) & ~ITEM_FLAG_WITH_FIELD;
+  with_flags= (with_flags | item_with_t::SUM_FUNC) & ~item_with_t::FIELD;
   window_func_sum_expr_flag= false;
 }
 
@@ -892,7 +892,7 @@ bool Aggregator_distinct::setup(THD *thd)
     */
 
     item_sum->null_value= 1;
-    item_sum->flags|= ITEM_FLAG_MAYBE_NULL;
+    item_sum->set_maybe_null();
     item_sum->quick_group= 0;
 
     DBUG_ASSERT(item_sum->get_arg(0)->fixed());
@@ -1125,9 +1125,8 @@ Item_sum_num::fix_fields(THD *thd, Item **ref)
     if (args[i]->fix_fields_if_needed_for_scalar(thd, &args[i]))
       return TRUE;
     set_if_bigger(decimals, args[i]->decimals);
-    flags|= (args[i]->flags & (ITEM_FLAG_WITH_SUBQUERY |
-                               ITEM_FLAG_WITH_PARAM |
-                               ITEM_FLAG_WITH_WINDOW_FUNC));
+    /* We should ignore FIELD's in arguments to sum functions */
+    with_flags|= (args[i]->with_flags & ~item_with_t::FIELD);
   }
   result_field=0;
   max_length=float_length(decimals);
@@ -1138,7 +1137,7 @@ Item_sum_num::fix_fields(THD *thd, Item **ref)
 
   if (arg_count)
     memcpy (orig_args, args, sizeof (Item *) * arg_count);
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
@@ -1156,10 +1155,8 @@ Item_sum_min_max::fix_fields(THD *thd, Item **ref)
   if (args[0]->fix_fields_if_needed_for_scalar(thd, &args[0]))
     DBUG_RETURN(TRUE);
 
-  flags|= (args[0]->flags & (ITEM_FLAG_WITH_SUBQUERY |
-                             ITEM_FLAG_WITH_PARAM |
-                             ITEM_FLAG_WITH_WINDOW_FUNC));
-
+  /* We should ignore FIELD's in arguments to sum functions */
+  with_flags|= (args[0]->with_flags & ~item_with_t::FIELD);
   if (fix_length_and_dec())
     DBUG_RETURN(TRUE);
 
@@ -1171,7 +1168,7 @@ Item_sum_min_max::fix_fields(THD *thd, Item **ref)
     DBUG_RETURN(TRUE);
 
   orig_args[0]= args[0];
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   DBUG_RETURN(FALSE);
 }
 
@@ -1241,7 +1238,7 @@ bool Item_sum_min_max::fix_length_and_dec()
   DBUG_ASSERT(args[0]->field_type() == args[0]->real_item()->field_type());
   DBUG_ASSERT(args[0]->result_type() == args[0]->real_item()->result_type());
   /* MIN/MAX can return NULL for empty set indepedent of the used column */
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   null_value= true;
   return args[0]->type_handler()->Item_sum_hybrid_fix_length_and_dec(this);
 }
@@ -1313,7 +1310,7 @@ Item_sum_sp::Item_sum_sp(THD *thd, Name_resolution_context *context_arg,
                            sp_name *name_arg, sp_head *sp, List<Item> &list)
   :Item_sum(thd, list), Item_sp(thd, context_arg, name_arg)
 {
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   quick_group= 0;
   m_sp= sp;
 }
@@ -1322,7 +1319,7 @@ Item_sum_sp::Item_sum_sp(THD *thd, Name_resolution_context *context_arg,
                            sp_name *name_arg, sp_head *sp)
   :Item_sum(thd), Item_sp(thd, context_arg, name_arg)
 {
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   quick_group= 0;
   m_sp= sp;
 }
@@ -1330,7 +1327,7 @@ Item_sum_sp::Item_sum_sp(THD *thd, Name_resolution_context *context_arg,
 Item_sum_sp::Item_sum_sp(THD *thd, Item_sum_sp *item):
              Item_sum(thd, item), Item_sp(thd, item)
 {
-  flags|= (item->flags & ITEM_FLAG_MAYBE_NULL);
+  base_flags|= (item->base_flags & item_base_t::MAYBE_NULL);
   quick_group= item->quick_group;
 }
 
@@ -1359,8 +1356,8 @@ Item_sum_sp::fix_fields(THD *thd, Item **ref)
     if (args[i]->fix_fields_if_needed_for_scalar(thd, &args[i]))
       return TRUE;
     set_if_bigger(decimals, args[i]->decimals);
-    flags|= (args[i]->flags & (ITEM_FLAG_WITH_SUBQUERY |
-                              ITEM_FLAG_WITH_WINDOW_FUNC));
+  /* We should ignore FIELD's in arguments to sum functions */
+    with_flags|= (args[i]->with_flags & ~item_with_t::FIELD);
   }
   result_field= NULL;
   max_length= float_length(decimals);
@@ -1373,7 +1370,7 @@ Item_sum_sp::fix_fields(THD *thd, Item **ref)
 
   if (arg_count)
     memcpy(orig_args, args, sizeof(Item *) * arg_count);
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
@@ -1557,7 +1554,7 @@ void Item_sum_sum::fix_length_and_dec_decimal()
 bool Item_sum_sum::fix_length_and_dec()
 {
   DBUG_ENTER("Item_sum_sum::fix_length_and_dec");
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   null_value=1;
   if (args[0]->cast_to_int_type_handler()->
       Item_sum_sum_fix_length_and_dec(this))
@@ -1980,7 +1977,7 @@ bool Item_sum_avg::fix_length_and_dec()
 {
   DBUG_ENTER("Item_sum_avg::fix_length_and_dec");
   prec_increment= current_thd->variables.div_precincrement;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   null_value=1;
   if (args[0]->cast_to_int_type_handler()->
       Item_sum_avg_fix_length_and_dec(this))
@@ -2211,7 +2208,7 @@ void Item_sum_variance::fix_length_and_dec_decimal()
 bool Item_sum_variance::fix_length_and_dec()
 {
   DBUG_ENTER("Item_sum_variance::fix_length_and_dec");
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   null_value= 1;
   prec_increment= current_thd->variables.div_precincrement;
 
@@ -4224,7 +4221,7 @@ Item_func_group_concat::fix_fields(THD *thd, Item **ref)
   if (init_sum_func_check(thd))
     return TRUE;
 
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
 
   /*
     Fix fields for select list and ORDER clause
@@ -4234,9 +4231,8 @@ Item_func_group_concat::fix_fields(THD *thd, Item **ref)
   {
     if (args[i]->fix_fields_if_needed_for_scalar(thd, &args[i]))
       return TRUE;
-    flags|= (args[i]->flags & (ITEM_FLAG_WITH_SUBQUERY |
-                               ITEM_FLAG_WITH_PARAM |
-                               ITEM_FLAG_WITH_WINDOW_FUNC));
+    /* We should ignore FIELD's in arguments to sum functions */
+    with_flags|= (args[i]->with_flags & ~item_with_t::FIELD);
   }
 
   /* skip charset aggregation for order columns */
@@ -4275,7 +4271,7 @@ Item_func_group_concat::fix_fields(THD *thd, Item **ref)
   if (check_sum_func(thd, ref))
     return TRUE;
 
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
diff --git a/sql/item_sum.h b/sql/item_sum.h
index 02da520048b..14672af6ef6 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -463,7 +463,7 @@ public:
   virtual void update_field()=0;
   virtual bool fix_length_and_dec()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     null_value=1;
     return FALSE;
   }
@@ -786,7 +786,7 @@ public:
   {
     decimals=0;
     max_length=21;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     null_value=0;
     return FALSE; }
 };
@@ -1219,7 +1219,7 @@ public:
     if (args[0]->check_type_can_return_int(func_name()))
       return true;
     decimals= 0; max_length=21; unsigned_flag= 1;
-    flags&= (item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    base_flags&= ~item_base_t::MAYBE_NULL;
     null_value= 0;
     return FALSE;
   }
@@ -1470,7 +1470,7 @@ public:
     :Item(thd), field(item->result_field)
   {
     name= item->name;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     decimals= item->decimals;
     max_length= item->max_length;
     unsigned_flag= item->unsigned_flag;
@@ -1614,7 +1614,7 @@ public:
     if (init_sum_func_check(thd))
       return TRUE;
 
-    flags|= ITEM_FLAG_FIXED;
+    base_flags|= item_base_t::FIXED;
     /*
       We set const_item_cache to false in constructors.
       It can be later changed to "true", in a Item_sum::make_const() call.
@@ -1846,7 +1846,8 @@ public:
     { DBUG_ASSERT(fixed()); null_value=1; return 0; }
   double val_real() { DBUG_ASSERT(fixed()); null_value=1; return 0.0; }
   longlong val_int() { DBUG_ASSERT(fixed()); null_value=1; return 0; }
-  bool fix_length_and_dec() { flags|= ITEM_FLAG_MAYBE_NULL; max_length=0; return FALSE; }
+  bool fix_length_and_dec() override
+  { base_flags|= item_base_t::MAYBE_NULL; max_length=0; return FALSE; }
   enum Sumfunctype sum_func () const { return UDF_SUM_FUNC; }
   void clear() {}
   bool add() { return 0; }  
diff --git a/sql/item_timefunc.cc b/sql/item_timefunc.cc
index 07bfbcddd14..89e5ead8270 100644
--- a/sql/item_timefunc.cc
+++ b/sql/item_timefunc.cc
@@ -967,7 +967,7 @@ bool Item_func_monthname::fix_length_and_dec()
   collation.set(cs, DERIVATION_COERCIBLE, locale->repertoire());
   decimals=0;
   max_length= locale->max_month_name_length * collation.collation->mbmaxlen;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -1112,7 +1112,7 @@ bool Item_func_dayname::fix_length_and_dec()
   collation.set(cs, DERIVATION_COERCIBLE, locale->repertoire());
   decimals=0;
   max_length= locale->max_day_name_length * collation.collation->mbmaxlen;
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -1761,7 +1761,7 @@ bool Item_func_date_format::fix_length_and_dec()
                    collation.collation->mbmaxlen;
     set_if_smaller(max_length,MAX_BLOB_WIDTH);
   }
-  flags|= ITEM_FLAG_MAYBE_NULL;					// If wrong date
+  set_maybe_null(); // If wrong date
   return FALSE;
 }
 
@@ -1924,7 +1924,7 @@ bool Item_func_from_unixtime::fix_length_and_dec()
     Type_temporal_attributes_not_fixed_dec(MAX_DATETIME_WIDTH,
                                            args[0]->decimals, false),
     DTCollation_numeric());
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return FALSE;
 }
 
@@ -2051,7 +2051,7 @@ bool Item_date_add_interval::fix_length_and_dec()
   {
     set_func_handler(&func_handler_date_add_interval_string);
   }
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return m_func_handler->fix_length_and_dec(this);
 }
 
@@ -2128,7 +2128,7 @@ bool Item_extract::check_arguments() const
 
 bool Item_extract::fix_length_and_dec()
 {
-  flags|= ITEM_FLAG_MAYBE_NULL;					// If wrong date
+  set_maybe_null(); // If wrong date
   uint32 daylen= args[0]->cmp_type() == TIME_RESULT ? 2 :
                  TIME_MAX_INTERVAL_DAY_CHAR_LENGTH;
   switch (int_type) {
@@ -2491,7 +2491,8 @@ Item_char_typecast::fix_length_and_dec_native_to_binary(uint32 octet_length)
 {
   collation.set(&my_charset_bin, DERIVATION_IMPLICIT);
   max_length= has_explicit_length() ? (uint32) cast_length : octet_length;
-  flags|= (current_thd->is_strict_mode() ? ITEM_FLAG_MAYBE_NULL : 0);
+  if (current_thd->is_strict_mode())
+    set_maybe_null();
 }
 
 
@@ -2536,7 +2537,8 @@ void Item_char_typecast::fix_length_and_dec_internal(CHARSET_INFO *from_cs)
                  args[0]->collation.collation->mbmaxlen));
   max_length= char_length * cast_cs->mbmaxlen;
   // Add NULL-ability in strict mode. See Item_str_func::fix_fields()
-  flags|= (current_thd->is_strict_mode() ? ITEM_FLAG_MAYBE_NULL : 0);
+  if (current_thd->is_strict_mode())
+    set_maybe_null();
 }
 
 
@@ -2660,7 +2662,7 @@ bool Item_func_add_time::fix_length_and_dec()
                                 &func_handler_add_time_string_sub);
   }
 
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   return m_func_handler->fix_length_and_dec(this);
 }
 
@@ -3046,7 +3048,7 @@ bool Item_func_str_to_date::fix_length_and_dec()
   if (collation.collation->mbminlen > 1)
     internal_charset= &my_charset_utf8mb4_general_ci;
 
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   set_func_handler(&func_handler_str_to_date_datetime_usec);
 
   if ((const_item= args[1]->const_item()))
diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index 26501dbd077..c717a7bde98 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -97,7 +97,7 @@ public:
   {
     decimals=0; 
     max_length=6*MY_CHARSET_BIN_MB_MAXLEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   enum_monotonicity_info get_monotonicity_info() const;
@@ -125,7 +125,7 @@ public:
   {
     decimals=0; 
     fix_char_length(12);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   enum_monotonicity_info get_monotonicity_info() const;
@@ -152,7 +152,7 @@ public:
   {
     decimals=0; 
     max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -177,7 +177,7 @@ public:
   {
     decimals= 0;
     fix_char_length(2);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -223,7 +223,7 @@ public:
   {
     decimals= 0;
     fix_char_length(3);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -247,7 +247,7 @@ public:
   {
     decimals=0;
     max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -271,7 +271,7 @@ public:
   {
     decimals=0;
     max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -295,7 +295,7 @@ public:
   {
      decimals=0;
      max_length=1*MY_CHARSET_BIN_MB_MAXLEN;
-     flags|= ITEM_FLAG_MAYBE_NULL;
+     set_maybe_null();
      return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -319,7 +319,7 @@ public:
   {
     decimals=0;
     max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -349,7 +349,7 @@ public:
   {
     decimals=0;
     max_length=2*MY_CHARSET_BIN_MB_MAXLEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_vcol_func_processor(void *arg)
@@ -382,7 +382,7 @@ public:
   {
     decimals=0;
     max_length=6*MY_CHARSET_BIN_MB_MAXLEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -408,7 +408,7 @@ public:
   {
     decimals=0;
     max_length=4*MY_CHARSET_BIN_MB_MAXLEN;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -441,7 +441,7 @@ public:
   {
     decimals= 0;
     fix_char_length(1);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool check_partition_func_processor(void *int_arg) {return FALSE;}
@@ -487,7 +487,7 @@ public:
     DBUG_ASSERT(dec <= TIME_SECOND_PART_DIGITS);
     decimals= dec;
     max_length=17 + (decimals ? decimals + 1 : 0);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     if (decimals)
       set_handler(&type_handler_newdecimal);
     else
@@ -906,7 +906,7 @@ class Item_func_convert_tz :public Item_datetimefunc
   bool fix_length_and_dec()
   {
     fix_attributes_datetime(args[0]->datetime_precision(current_thd));
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool get_date(THD *thd, MYSQL_TIME *res, date_mode_t fuzzydate);
@@ -926,7 +926,7 @@ public:
   bool fix_length_and_dec()
   {
     fix_attributes_time(args[0]->decimals);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   const char *func_name() const { return "sec_to_time"; }
@@ -1214,7 +1214,7 @@ public:
     uint dec0= args[0]->datetime_precision(thd);
     uint dec1= Interval_DDhhmmssff::fsp(thd, args[1]);
     fix_attributes_datetime(MY_MAX(dec0, dec1));
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return false;
   }
   bool get_date(THD *thd, MYSQL_TIME *ltime, date_mode_t fuzzydate)
@@ -1274,7 +1274,7 @@ public:
     uint dec= MY_MAX(args[0]->time_precision(thd),
                      args[1]->time_precision(thd));
     fix_attributes_time(dec);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   bool get_date(THD *thd, MYSQL_TIME *ltime, date_mode_t fuzzydate);
@@ -1296,7 +1296,7 @@ public:
   bool fix_length_and_dec()
   {
     fix_attributes_time(args[2]->decimals);
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   const char *func_name() const { return "maketime"; }
@@ -1315,7 +1315,7 @@ public:
   bool fix_length_and_dec()
   {
     decimals=0;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     fix_char_length(6);
     return FALSE;
   }
@@ -1346,7 +1346,7 @@ public:
   bool fix_length_and_dec()
   {
     decimals=0;
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     return FALSE;
   }
   virtual void print(String *str, enum_query_type query_type);
@@ -1371,7 +1371,7 @@ public:
   const char *func_name() const { return "get_format"; }
   bool fix_length_and_dec()
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
     decimals=0;
     fix_length_and_charset(17, default_charset());
     return FALSE;
diff --git a/sql/item_windowfunc.cc b/sql/item_windowfunc.cc
index cdf8ebf9879..262481d019b 100644
--- a/sql/item_windowfunc.cc
+++ b/sql/item_windowfunc.cc
@@ -120,7 +120,7 @@ Item_window_func::fix_fields(THD *thd, Item **ref)
 
   const_item_cache= false;
 
-  flags= (flags & ~ITEM_FLAG_WITH_SUM_FUNC) | ITEM_FLAG_WITH_WINDOW_FUNC;
+  with_flags= (with_flags & ~item_with_t::SUM_FUNC) | item_with_t::WINDOW_FUNC;
 
   if (fix_length_and_dec())
     return TRUE;
@@ -128,7 +128,7 @@ Item_window_func::fix_fields(THD *thd, Item **ref)
   max_length= window_func()->max_length;
   set_maybe_null(window_func()->maybe_null());
 
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   set_phase_to_initial();
   return false;
 }
@@ -344,8 +344,7 @@ bool Item_sum_hybrid_simple::fix_fields(THD *thd, Item **ref)
   {
     if (args[i]->fix_fields_if_needed_for_scalar(thd, &args[i]))
       return TRUE;
-    flags|= (args[i]->flags & (ITEM_FLAG_WITH_WINDOW_FUNC |
-                               ITEM_FLAG_WITH_SUBQUERY));
+    with_flags|= args[i]->with_flags;
   }
 
   if (fix_length_and_dec())
@@ -359,14 +358,14 @@ bool Item_sum_hybrid_simple::fix_fields(THD *thd, Item **ref)
   for (uint i= 0; i < arg_count; i++)
     orig_args[i]= args[i];
 
-  flags|= ITEM_FLAG_FIXED;
+  base_flags|= item_base_t::FIXED;
   return FALSE;
 }
 
 
 bool Item_sum_hybrid_simple::fix_length_and_dec()
 {
-  flags|= ITEM_FLAG_MAYBE_NULL;
+  set_maybe_null();
   null_value= true;
   return args[0]->type_handler()->Item_sum_hybrid_fix_length_and_dec(this);
 }
diff --git a/sql/item_xmlfunc.h b/sql/item_xmlfunc.h
index 3369304d79c..1d2b6e70995 100644
--- a/sql/item_xmlfunc.h
+++ b/sql/item_xmlfunc.h
@@ -110,12 +110,12 @@ protected:
 public:
   Item_xml_str_func(THD *thd, Item *a, Item *b): Item_str_func(thd, a, b)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   Item_xml_str_func(THD *thd, Item *a, Item *b, Item *c):
     Item_str_func(thd, a, b, c)
   {
-    flags|= ITEM_FLAG_MAYBE_NULL;
+    set_maybe_null();
   }
   bool fix_fields(THD *thd, Item **ref);
   bool fix_length_and_dec();
diff --git a/sql/opt_subselect.cc b/sql/opt_subselect.cc
index 84741adc3fd..3a30fd93e95 100644
--- a/sql/opt_subselect.cc
+++ b/sql/opt_subselect.cc
@@ -966,7 +966,7 @@ bool make_in_exists_conversion(THD *thd, JOIN *join, Item_in_subselect *item)
     call.
   */
   item->changed= 0;
-  item->flags|= ITEM_FLAG_FIXED;
+  item->base_flags|= item_base_t::FIXED;
 
   SELECT_LEX *save_select_lex= thd->lex->current_select;
   thd->lex->current_select= item->unit->first_select();
@@ -1318,7 +1318,7 @@ bool convert_join_subqueries_to_semijoins(JOIN *join)
   {
     JOIN *child_join= in_subq->unit->first_select()->join;
     in_subq->changed= 0;
-    in_subq->flags|= ITEM_FLAG_FIXED;
+    in_subq->base_flags|= item_base_t::FIXED;
 
     SELECT_LEX *save_select_lex= thd->lex->current_select;
     thd->lex->current_select= in_subq->unit->first_select();
diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index 46a9141899e..e3b212ff3b4 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -2992,7 +2992,7 @@ sp_head::show_create_routine_get_fields(THD *thd, const Sp_handler *sph,
 
     Item_empty_string *stmt_fld=
       new (mem_root) Item_empty_string(thd, col3_caption, 1024);
-    stmt_fld->flags|= ITEM_FLAG_MAYBE_NULL;
+    stmt_fld->set_maybe_null();
 
     fields->push_back(stmt_fld, mem_root);
   }
@@ -3068,7 +3068,7 @@ sp_head::show_create_routine(THD *thd, const Sp_handler *sph)
       new (mem_root) Item_empty_string(thd, col3_caption,
                             (uint)MY_MAX(m_defstr.length, 1024));
 
-    stmt_fld->flags|= ITEM_FLAG_MAYBE_NULL;
+    stmt_fld->set_maybe_null();
 
     fields.push_back(stmt_fld, thd->mem_root);
   }
diff --git a/sql/sql_admin.cc b/sql/sql_admin.cc
index 1ee21954945..c18ca6286fa 100644
--- a/sql/sql_admin.cc
+++ b/sql/sql_admin.cc
@@ -509,18 +509,18 @@ static bool mysql_admin_table(THD* thd, TABLE_LIST* tables,
   field_list.push_back(item= new (thd->mem_root)
                        Item_empty_string(thd, "Table",
                                          NAME_CHAR_LEN * 2), thd->mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item= new (thd->mem_root)
                        Item_empty_string(thd, "Op", 10), thd->mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item= new (thd->mem_root)
                        Item_empty_string(thd, "Msg_type", 10), thd->mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item= new (thd->mem_root)
                        Item_empty_string(thd, "Msg_text",
                                          SQL_ADMIN_MSG_TEXT_SIZE),
                        thd->mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   if (protocol->send_result_set_metadata(&field_list,
                             Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
     DBUG_RETURN(TRUE);
diff --git a/sql/sql_analyse.cc b/sql/sql_analyse.cc
index 090fd724873..a6fc7c25e55 100644
--- a/sql/sql_analyse.cc
+++ b/sql/sql_analyse.cc
@@ -1165,16 +1165,16 @@ bool analyse::change_columns(THD *thd, List<Item> &field_list)
 
   func_items[0]= new (mem_root) Item_proc_string(thd, "Field_name", 255);
   func_items[1]= new (mem_root) Item_proc_string(thd, "Min_value", 255);
-  func_items[1]->flags|= ITEM_FLAG_MAYBE_NULL;
+  func_items[1]->set_maybe_null();
   func_items[2]= new (mem_root) Item_proc_string(thd, "Max_value", 255);
-  func_items[2]->flags|= ITEM_FLAG_MAYBE_NULL;
+  func_items[2]->set_maybe_null();
   func_items[3]= new (mem_root) Item_proc_int(thd, "Min_length");
   func_items[4]= new (mem_root) Item_proc_int(thd, "Max_length");
   func_items[5]= new (mem_root) Item_proc_int(thd, "Empties_or_zeros");
   func_items[6]= new (mem_root) Item_proc_int(thd, "Nulls");
   func_items[7]= new (mem_root) Item_proc_string(thd, "Avg_value_or_avg_length", 255);
   func_items[8]= new (mem_root) Item_proc_string(thd, "Std", 255);
-  func_items[8]->flags|= ITEM_FLAG_MAYBE_NULL;
+  func_items[8]->set_maybe_null();
   func_items[9]= new (mem_root) Item_proc_string(thd, "Optimal_fieldtype",
                                                   MY_MAX(64,
                                                          output_str_length));
diff --git a/sql/sql_class.cc b/sql/sql_class.cc
index 8c3bc955a5a..4a3d8cdc2b0 100644
--- a/sql/sql_class.cc
+++ b/sql/sql_class.cc
@@ -2748,45 +2748,45 @@ void THD::make_explain_field_list(List<Item> &field_list, uint8 explain_flags,
   field_list.push_back(item= new (mem_root)
                        Item_return_int(this, "id", 3,
                                        MYSQL_TYPE_LONGLONG), mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(new (mem_root)
                        Item_empty_string(this, "select_type", 19, cs),
                        mem_root);
   field_list.push_back(item= new (mem_root)
                        Item_empty_string(this, "table", NAME_CHAR_LEN, cs),
                        mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   if (explain_flags & DESCRIBE_PARTITIONS)
   {
     /* Maximum length of string that make_used_partitions_str() can produce */
     item= new (mem_root) Item_empty_string(this, "partitions",
                                            MAX_PARTITIONS * (1 + FN_LEN), cs);
     field_list.push_back(item, mem_root);
-    item->flags|= ITEM_FLAG_MAYBE_NULL;
+    item->set_maybe_null();
   }
   field_list.push_back(item= new (mem_root)
                        Item_empty_string(this, "type", 10, cs),
                        mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item= new (mem_root)
                        Item_empty_string(this, "possible_keys",
                                          NAME_CHAR_LEN*MAX_KEY, cs),
                        mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item=new (mem_root)
                        Item_empty_string(this, "key", NAME_CHAR_LEN, cs),
                        mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item=new (mem_root)
                        Item_empty_string(this, "key_len",
                                          NAME_CHAR_LEN*MAX_KEY),
                        mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item=new (mem_root)
                        Item_empty_string(this, "ref",
                                          NAME_CHAR_LEN*MAX_REF_PARTS, cs),
                        mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item=new (mem_root)
                        Item_empty_string(this, "rows", NAME_CHAR_LEN, cs),
                        mem_root);
@@ -2795,7 +2795,7 @@ void THD::make_explain_field_list(List<Item> &field_list, uint8 explain_flags,
     field_list.push_back(item= new (mem_root)
                          Item_empty_string(this, "r_rows", NAME_CHAR_LEN, cs),
                          mem_root);
-    item->flags|= ITEM_FLAG_MAYBE_NULL;
+    item->set_maybe_null();
   }
 
   if (is_analyze || (explain_flags & DESCRIBE_EXTENDED))
@@ -2803,7 +2803,7 @@ void THD::make_explain_field_list(List<Item> &field_list, uint8 explain_flags,
     field_list.push_back(item= new (mem_root)
                          Item_float(this, "filtered", 0.1234, 2, 4),
                          mem_root);
-    item->flags|= ITEM_FLAG_MAYBE_NULL;
+    item->set_maybe_null();
   }
 
   if (is_analyze)
@@ -2811,10 +2811,10 @@ void THD::make_explain_field_list(List<Item> &field_list, uint8 explain_flags,
     field_list.push_back(item= new (mem_root)
                          Item_float(this, "r_filtered", 0.1234, 2, 4),
                          mem_root);
-    item->flags|= ITEM_FLAG_MAYBE_NULL;
+    item->set_maybe_null();
   }
 
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(new (mem_root)
                        Item_empty_string(this, "Extra", 255, cs),
                        mem_root);
diff --git a/sql/sql_cte.cc b/sql/sql_cte.cc
index c262adc763d..faa2b424f12 100644
--- a/sql/sql_cte.cc
+++ b/sql/sql_cte.cc
@@ -992,7 +992,7 @@ With_element::process_columns_of_derived_unit(THD *thd,
     while ((item= it++, name= nm++))
     {
       item->set_name(thd, *name);
-      item->flags&= ~ITEM_FLAG_IS_AUTOGENERATED_NAME;
+      item->base_flags&= ~item_base_t::IS_AUTOGENERATED_NAME;
     }
 
     if (arena)
@@ -1035,7 +1035,7 @@ With_element::process_columns_of_derived_unit(THD *thd,
         my_error(ER_BAD_FIELD_ERROR, MYF(0), name->str, "CYCLE clause");
         return true;
       }
-      item->flags|= ITEM_FLAG_IS_IN_WITH_CYCLE;
+      item->base_flags|= item_base_t::IS_IN_WITH_CYCLE;
     }
   }
   unit->columns_are_renamed= true;
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 732cc0b28a9..881eaa034ee 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -18500,7 +18500,7 @@ bool Create_tmp_table::add_fields(THD *thd,
               new_field->maybe_null() is still false, it will be
               changed below. But we have to setup Item_field correctly
             */
-            arg->flags|= ITEM_FLAG_MAYBE_NULL;
+            arg->set_maybe_null();
           }
           if (current_counter == distinct)
             new_field->flags|= FIELD_PART_OF_TMP_UNIQUE;
@@ -18890,7 +18890,7 @@ bool Create_tmp_table::finalize(THD *thd,
             that the key,field and item definition match.
           */
           maybe_null= 0;
-          (*cur_group->item)->flags&= (Item::item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+          (*cur_group->item)->base_flags&= ~item_base_t::MAYBE_NULL;
         }
 
 	if (!(cur_group->field= field->new_key_field(thd->mem_root,table,
@@ -24812,7 +24812,7 @@ count_field_types(SELECT_LEX *select_lex, TMP_TABLE_PARAM *param,
     {
       param->func_count++;
       if (reset_with_sum_func)
-	field->flags&= ~ITEM_FLAG_WITH_SUM_FUNC;
+	field->with_flags&= ~item_with_t::SUM_FUNC;
     }
   }
 }
@@ -25867,7 +25867,7 @@ static bool change_group_ref(THD *thd, Item_func *expr, ORDER *group_list,
     }
     if (arg_changed)
     {
-      expr->flags|= ITEM_FLAG_MAYBE_NULL | ITEM_FLAG_IN_ROLLUP;
+      expr->base_flags|= item_base_t::MAYBE_NULL | item_base_t::IN_ROLLUP;
       *changed= TRUE;
     }
   }
@@ -25938,7 +25938,7 @@ bool JOIN::rollup_init()
     {
       if (*group_tmp->item == item)
       {
-        item->flags|= ITEM_FLAG_MAYBE_NULL | ITEM_FLAG_IN_ROLLUP;
+        item->base_flags|= item_base_t::MAYBE_NULL | item_base_t::IN_ROLLUP;
         found_in_group= 1;
         break;
       }
@@ -25954,7 +25954,7 @@ bool JOIN::rollup_init()
         Marking the expression item as 'with_sum_func' will ensure this.
       */ 
       if (changed)
-        item->flags|= ITEM_FLAG_WITH_SUM_FUNC;
+        item->with_flags|= item_with_t::SUM_FUNC;
     }
   }
   return 0;
@@ -26124,7 +26124,8 @@ bool JOIN::rollup_make_fields(List<Item> &fields_arg, List<Item> &sel_fields,
             Item_null_result *null_item= new (thd->mem_root) Item_null_result(thd);
             if (!null_item)
               return 1;
-	    item->flags|= ITEM_FLAG_MAYBE_NULL;		// Value will be null sometimes
+            // Value will be null sometimes
+	    item->set_maybe_null();
             null_item->result_field= item->get_tmp_table_field();
             item= null_item;
 	    break;
diff --git a/sql/sql_show.cc b/sql/sql_show.cc
index df5d844e46b..978843234bc 100644
--- a/sql/sql_show.cc
+++ b/sql/sql_show.cc
@@ -2858,7 +2858,7 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
   field_list.push_back(field=new (mem_root)
                        Item_empty_string(thd, "db", NAME_CHAR_LEN),
                        mem_root);
-  field->flags|= ITEM_FLAG_MAYBE_NULL;;
+  field->set_maybe_null();;
   field_list.push_back(new (mem_root) Item_empty_string(thd, "Command", 16),
                        mem_root);
   field_list.push_back(field= new (mem_root)
@@ -2868,18 +2868,18 @@ void mysqld_list_processes(THD *thd,const char *user, bool verbose)
   field_list.push_back(field=new (mem_root)
                        Item_empty_string(thd, "State", 30),
                        mem_root);
-  field->flags|= ITEM_FLAG_MAYBE_NULL;;
+  field->set_maybe_null();;
   field_list.push_back(field=new (mem_root)
                        Item_empty_string(thd, "Info", arg.max_query_length),
                        mem_root);
-  field->flags|= ITEM_FLAG_MAYBE_NULL;;
+  field->set_maybe_null();;
   if (!thd->variables.old_mode &&
       !(thd->variables.old_behavior & OLD_MODE_NO_PROGRESS_INFO))
   {
     field_list.push_back(field= new (mem_root)
                          Item_float(thd, "Progress", 0.0, 3, 7),
                          mem_root);
-    field->flags&= (Item::item_flags_t) ~ITEM_FLAG_MAYBE_NULL;
+    field->base_flags&= ~item_base_t::MAYBE_NULL;
   }
   if (protocol->send_result_set_metadata(&field_list,
                                          Protocol::SEND_NUM_ROWS |
@@ -9723,7 +9723,7 @@ static bool show_create_trigger_impl(THD *thd, Trigger *trigger)
                                        (uint)MY_MAX(trg_sql_original_stmt.length,
                                               1024));
 
-    stmt_fld->flags|= ITEM_FLAG_MAYBE_NULL;
+    stmt_fld->set_maybe_null();
 
     fields.push_back(stmt_fld, mem_root);
   }
diff --git a/sql/sql_table.cc b/sql/sql_table.cc
index 696982ae617..23c9f5198ca 100644
--- a/sql/sql_table.cc
+++ b/sql/sql_table.cc
@@ -11668,12 +11668,12 @@ bool mysql_checksum_table(THD *thd, TABLE_LIST *tables,
   field_list.push_back(item= new (thd->mem_root)
                        Item_empty_string(thd, "Table", NAME_LEN*2),
                        thd->mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   field_list.push_back(item= new (thd->mem_root)
                        Item_int(thd, "Checksum", (longlong) 1,
                                 MY_INT64_NUM_DECIMAL_DIGITS),
                        thd->mem_root);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   if (protocol->send_result_set_metadata(&field_list,
                             Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
     DBUG_RETURN(TRUE);
diff --git a/sql/sql_type.cc b/sql/sql_type.cc
index 7e1d4f05238..8f27dbedd89 100644
--- a/sql/sql_type.cc
+++ b/sql/sql_type.cc
@@ -4717,7 +4717,8 @@ bool Type_handler_temporal_result::
       continue; // No conversion.
     if (ha->cmp_type() != TIME_RESULT)
     {
-      func->flags|= ITEM_FLAG_MAYBE_NULL; // Conversion from non-temporal is not safe
+      // Conversion from non-temporal is not safe
+      func->set_maybe_null();
       break;
     }
     timestamp_type tf= hf->mysql_timestamp_type();
@@ -4768,7 +4769,7 @@ bool Type_handler_temporal_result::
     DBUG_ASSERT(hf->field_type() == MYSQL_TYPE_DATETIME);
     if (!(thd->variables.old_behavior & OLD_MODE_ZERO_DATE_TIME_CAST))
       continue;
-    func->flags|= ITEM_FLAG_MAYBE_NULL;
+    func->set_maybe_null();
     break;
   }
   return rc;
@@ -4792,7 +4793,7 @@ bool Type_handler_date_common::
   {
     if (items[i]->type_handler()->cmp_type() != TIME_RESULT)
     {
-      func->flags|= ITEM_FLAG_MAYBE_NULL;
+      func->set_maybe_null();
       break;
     }
   }
@@ -6674,7 +6675,7 @@ bool Type_handler::
             item->arguments()[0]->time_precision(current_thd) :
             item->decimals;
   item->fix_attributes_temporal(MIN_TIME_WIDTH, dec);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   return false;
 }
 
@@ -6683,7 +6684,7 @@ bool Type_handler::
        Item_date_typecast_fix_length_and_dec(Item_date_typecast *item) const
 {
   item->fix_attributes_temporal(MAX_DATE_WIDTH, 0);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   return false;
 }
 
@@ -6696,7 +6697,7 @@ bool Type_handler::
             item->arguments()[0]->datetime_precision(current_thd) :
             item->decimals;
   item->fix_attributes_temporal(MAX_DATETIME_WIDTH, dec);
-  item->flags|= ITEM_FLAG_MAYBE_NULL;
+  item->set_maybe_null();
   return false;
 }
 
diff --git a/sql/sql_view.cc b/sql/sql_view.cc
index 57c0c2e2ccd..dd41cfd3e84 100644
--- a/sql/sql_view.cc
+++ b/sql/sql_view.cc
@@ -137,7 +137,7 @@ bool check_duplicate_names(THD *thd, List<Item> &item_list, bool gen_unique_view
     Item *check;
     /* treat underlying fields like set by user names */
     if (item->real_item()->type() == Item::FIELD_ITEM)
-      item->flags&= ~ITEM_FLAG_IS_AUTOGENERATED_NAME;
+      item->base_flags&= ~item_base_t::IS_AUTOGENERATED_NAME;
     itc.rewind();
     while ((check= itc++) && check != item)
     {
@@ -566,7 +566,7 @@ bool mysql_create_view(THD *thd, TABLE_LIST *views,
     while ((item= it++, name= nm++))
     {
       item->set_name(thd, *name);
-      item->flags&= ~ITEM_FLAG_IS_AUTOGENERATED_NAME;
+      item->base_flags&= ~item_base_t::IS_AUTOGENERATED_NAME;
     }
   }
 
diff --git a/sql/sql_yacc.yy b/sql/sql_yacc.yy
index 499d02c0d74..d9b28610748 100644
--- a/sql/sql_yacc.yy
+++ b/sql/sql_yacc.yy
@@ -9154,7 +9154,7 @@ select_item:
               if (unlikely(Lex->sql_command == SQLCOM_CREATE_VIEW &&
                           check_column_name($4.str)))
                 my_yyabort_error((ER_WRONG_COLUMN_NAME, MYF(0), $4.str));
-              $2->flags&= ~ITEM_FLAG_IS_AUTOGENERATED_NAME;
+              $2->base_flags&= ~item_base_t::IS_AUTOGENERATED_NAME;
               $2->set_name(thd, $4);
             }
             else if (!$2->name.str || $2->name.str == item_empty_name)
@@ -10732,7 +10732,7 @@ udf_expr:
             */
             if ($4.str)
             {
-              $2->flags&= ~ITEM_FLAG_IS_AUTOGENERATED_NAME;
+              $2->base_flags&= ~item_base_t::IS_AUTOGENERATED_NAME;
               $2->set_name(thd, $4);
             }
             /* 
diff --git a/sql/table.cc b/sql/table.cc
index aae2bda2b4a..200e4830b94 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -6765,7 +6765,7 @@ Item *create_view_field(THD *thd, TABLE_LIST *view, Item **field_ref,
     views/derived tables.
   */
   if (view->table && view->table->maybe_null)
-    item->flags|= ITEM_FLAG_MAYBE_NULL;
+    item->set_maybe_null();
   /* Save item in case we will need to fall back to materialization. */
   view->used_items.push_front(item, thd->mem_root);
   /*