sql/handler: referenced_by_foreign_key() returns bool

The method was declared to return an unsigned integer, but it is
really a boolean (and used as such by all callers).

A secondary change is the addition of "const" and "noexcept" to this
method.

In ha_mroonga.cpp, I also added "inline" to the two helper methods of
referenced_by_foreign_key().  This allows the compiler to flatten the
method.

sql/ha_partition.h

@@ -1464,7 +1464,7 @@ class ha_partition :public handler
 
     virtual int get_foreign_key_list(THD *thd,
     List<FOREIGN_KEY_INFO> *f_key_list)
-    virtual uint referenced_by_foreign_key()
+    bool referenced_by_foreign_key() const noexcept override
   */
     bool can_switch_engines() override;
   /*

sql/handler.h

@@ -4078,7 +4078,7 @@ class handler :public Sql_alloc
   virtual int
   get_parent_foreign_key_list(THD *thd, List<FOREIGN_KEY_INFO> *f_key_list)
   { return 0; }
-  virtual uint referenced_by_foreign_key() { return 0;}
+  virtual bool referenced_by_foreign_key() const noexcept { return false;}
   virtual void init_table_handle_for_HANDLER()
   { return; }       /* prepare InnoDB for HANDLER */
   virtual void free_foreign_key_create_info(char* str) {}

storage/innobase/handler/ha_innodb.cc

@@ -10052,8 +10052,8 @@ wsrep_append_key(
 static bool
 referenced_by_foreign_key2(
 /*=======================*/
-	dict_table_t* table,
-	dict_index_t* index)
+	const dict_table_t* table,
+	const dict_index_t* index) noexcept
 {
 	ut_ad(table != NULL);
 	ut_ad(index != NULL);
@@ -15451,16 +15451,12 @@ ha_innobase::can_switch_engines(void)
 	DBUG_RETURN(can_switch);
 }
 
-/*******************************************************************//**
-Checks if a table is referenced by a foreign key. The MySQL manual states that
-a REPLACE is either equivalent to an INSERT, or DELETE(s) + INSERT. Only a
+/** Checks if a table is referenced by a foreign key. The MySQL manual states
+that a REPLACE is either equivalent to an INSERT, or DELETE(s) + INSERT. Only a
 delete is then allowed internally to resolve a duplicate key conflict in
 REPLACE, not an update.
-@return > 0 if referenced by a FOREIGN KEY */
-
-uint
-ha_innobase::referenced_by_foreign_key(void)
-/*========================================*/
+@return whether the table is referenced by a FOREIGN KEY */
+bool ha_innobase::referenced_by_foreign_key() const noexcept
 {
 	if (dict_table_is_referenced_by_foreign_key(m_prebuilt->table)) {
 

storage/innobase/handler/ha_innodb.h

@@ -222,7 +222,7 @@ class ha_innobase final : public handler
 
 	bool can_switch_engines() override;
 
-	uint referenced_by_foreign_key() override;
+	bool referenced_by_foreign_key() const noexcept override;
 
 	void free_foreign_key_create_info(char* str) override;
 

storage/mroonga/ha_mroonga.cpp

@@ -16790,10 +16790,10 @@ int ha_mroonga::get_parent_foreign_key_list(THD *thd,
   DBUG_RETURN(res);
 }
 
-uint ha_mroonga::wrapper_referenced_by_foreign_key()
+inline bool ha_mroonga::wrapper_referenced_by_foreign_key() const noexcept
 {
   MRN_DBUG_ENTER_METHOD();
-  uint res;
+  bool res;
   MRN_SET_WRAP_SHARE_KEY(share, table->s);
   MRN_SET_WRAP_TABLE_KEY(this, table);
   res = wrap_handler->referenced_by_foreign_key();
@@ -16802,17 +16802,17 @@ uint ha_mroonga::wrapper_referenced_by_foreign_key()
   DBUG_RETURN(res);
 }
 
-uint ha_mroonga::storage_referenced_by_foreign_key()
+inline bool ha_mroonga::storage_referenced_by_foreign_key() const noexcept
 {
   MRN_DBUG_ENTER_METHOD();
-  uint res = handler::referenced_by_foreign_key();
+  bool res = handler::referenced_by_foreign_key();
   DBUG_RETURN(res);
 }
 
-uint ha_mroonga::referenced_by_foreign_key()
+bool ha_mroonga::referenced_by_foreign_key() const noexcept
 {
   MRN_DBUG_ENTER_METHOD();
-  uint res;
+  bool res;
   if (share->wrapper_mode)
   {
     res = wrapper_referenced_by_foreign_key();

storage/mroonga/ha_mroonga.hpp

@@ -618,7 +618,7 @@ protected:
   bool can_switch_engines() mrn_override;
   int get_foreign_key_list(THD *thd, List<FOREIGN_KEY_INFO> *f_key_list) mrn_override;
   int get_parent_foreign_key_list(THD *thd, List<FOREIGN_KEY_INFO> *f_key_list) mrn_override;
-  uint referenced_by_foreign_key() mrn_override;
+  bool referenced_by_foreign_key() const noexcept mrn_override;
   void init_table_handle_for_HANDLER() mrn_override;
   void free_foreign_key_create_info(char* str) mrn_override;
 #ifdef MRN_HAVE_HA_REBIND_PSI
@@ -1268,8 +1268,8 @@ private:
   int storage_get_foreign_key_list(THD *thd, List<FOREIGN_KEY_INFO> *f_key_list);
   int wrapper_get_parent_foreign_key_list(THD *thd, List<FOREIGN_KEY_INFO> *f_key_list);
   int storage_get_parent_foreign_key_list(THD *thd, List<FOREIGN_KEY_INFO> *f_key_list);
-  uint wrapper_referenced_by_foreign_key();
-  uint storage_referenced_by_foreign_key();
+  bool wrapper_referenced_by_foreign_key() const noexcept;
+  bool storage_referenced_by_foreign_key() const noexcept;
   void wrapper_init_table_handle_for_HANDLER();
   void storage_init_table_handle_for_HANDLER();
   void wrapper_free_foreign_key_create_info(char* str);