1 files changed, 62 insertions, 29 deletions

diff --git a/sql/item.h b/sql/item.h
index 486ca098dda..07a3d476699 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -772,8 +772,8 @@ enum class item_base_t : item_flags_t
   FIXED=                 (1<<2),   // Was fixed with fix_fields().
   IS_EXPLICIT_NAME=      (1<<3),   // The name of this Item was set by the user
                                    // (or was auto generated otherwise)
-  IS_IN_WITH_CYCLE=      (1<<4)    // This item is in CYCLE clause
-                                   // of WITH.
+  IS_IN_WITH_CYCLE=      (1<<4),   // This item is in CYCLE clause of WITH.
+  AT_TOP_LEVEL=          (1<<5)    // At top (AND) level of item tree
 };
 
 
@@ -1327,6 +1327,25 @@ public:
   {
     set_maybe_null(maybe_null_arg);
   }
+  /*
+    Mark the item that it is a top level item, or part of a top level AND item,
+    for WHERE and ON clauses:
+    Example:   ... WHERE a=5 AND b=6;   Both a=5 and b=6 are top level items
+
+    This is used to indicate that there is no distinction between if the
+    value of the item is FALSE or NULL..
+    This enables Item_cond_and and subquery related items to do special
+    "top level" optimizations.
+  */
+  virtual void top_level_item()
+  {
+    base_flags|= item_base_t::AT_TOP_LEVEL;
+  }
+  /*
+    Return TRUE if this item of top WHERE level (AND/OR)
+  */
+  bool is_top_level_item() const
+  { return (bool) (base_flags & item_base_t::AT_TOP_LEVEL); }
 
   void set_typelib(const TYPELIB *typelib) override
   {
@@ -1833,6 +1852,16 @@ public:
   */
   virtual bool is_evaluable_expression() const { return true; }
 
+  virtual bool check_assignability_to(const Field *to, bool ignore) const
+  {
+    /*
+      "this" must be neither DEFAULT/IGNORE,
+      nor Item_param bound to DEFAULT/IGNORE.
+    */
+    DBUG_ASSERT(is_evaluable_expression());
+    return to->check_assignability_from(type_handler(), ignore);
+  }
+
   /**
    * Check whether the item is a parameter  ('?') of stored routine.
    * Default implementation returns false. Method is overridden in the class
@@ -2049,25 +2078,6 @@ public:
   {
     return type_handler()->Item_update_null_value(this);
   }
-
-  /*
-    Inform the item that there will be no distinction between its result
-    being FALSE or NULL.
-
-    NOTE
-      This function will be called for eg. Items that are top-level AND-parts
-      of the WHERE clause. Items implementing this function (currently
-      Item_cond_and and subquery-related item) enable special optimizations
-      when they are "top level".
-  */
-  virtual void top_level_item() {}
-  /*
-    Return TRUE if it is item of top WHERE level (AND/OR)  and it is
-    important, return FALSE if it not important (we can not use to simplify
-    calculations) or not top level
-  */
-  virtual bool is_top_level_item() const
-  { return FALSE; /* not important */}
   /*
     return IN/ALL/ANY subquery or NULL
   */
@@ -2677,18 +2687,27 @@ public:
   void register_in(THD *thd);	 
   
   bool depends_only_on(table_map view_map) 
-  { return marker & MARKER_FULL_EXTRACTION; }
-  int get_extraction_flag()
-  { return marker & MARKER_EXTRACTION_MASK; }
+  { return get_extraction_flag() & MARKER_FULL_EXTRACTION; }
+   int get_extraction_flag() const
+  {
+    if (basic_const_item())
+      return MARKER_FULL_EXTRACTION;
+    else
+      return marker & MARKER_EXTRACTION_MASK;
+  }
   void set_extraction_flag(int16 flags)
   {
-    marker &= ~MARKER_EXTRACTION_MASK;
-    marker|= flags;
+    if (!basic_const_item())
+    {
+      marker= marker & ~MARKER_EXTRACTION_MASK;
+      marker|= flags;
+    }
   }
   void clear_extraction_flag()
   {
-    marker &= ~MARKER_EXTRACTION_MASK;
-  }
+    if (!basic_const_item())
+      marker= marker & ~MARKER_EXTRACTION_MASK;
+   }
   void check_pushable_cond(Pushdown_checker excl_dep_func, uchar *arg);
   bool pushable_cond_checker_for_derived(uchar *arg)
   {
@@ -4124,6 +4143,7 @@ class Item_param :public Item_basic_value,
   const String *value_query_val_str(THD *thd, String* str) const;
   Item *value_clone_item(THD *thd);
   bool is_evaluable_expression() const override;
+  bool check_assignability_to(const Field *field, bool ignore) const override;
   bool can_return_value() const;
 
 public:
@@ -4470,11 +4490,16 @@ public:
   Item_bool_static(const char *str_arg, longlong i):
     Item_bool(str_arg, i) {};
 
+  /* Don't mark static items as top level item */
+  virtual void top_level_item() override {}
   void set_join_tab_idx(uint8 join_tab_idx_arg) override
   { DBUG_ASSERT(0); }
+
+  void cleanup() override {}
 };
 
-extern const Item_bool_static Item_false, Item_true;
+/* The following variablese are stored in a read only segment */
+extern Item_bool_static *Item_false, *Item_true;
 
 class Item_uint :public Item_int
 {
@@ -6808,6 +6833,10 @@ public:
   {
     str->append(STRING_WITH_LEN("default"));
   }
+  bool check_assignability_to(const Field *to, bool ignore) const override
+  {
+    return false;
+  }
   int save_in_field(Field *field_arg, bool) override
   {
     return field_arg->save_in_field_default_value(false);
@@ -6841,6 +6870,10 @@ public:
   {
     str->append(STRING_WITH_LEN("ignore"));
   }
+  bool check_assignability_to(const Field *to, bool ignore) const override
+  {
+    return false;
+  }
   int save_in_field(Field *field_arg, bool) override
   {
     return field_arg->save_in_field_ignore_value(false);