cleanup: Sp_caches::sp_caches_swap()

remove the fix for MDEV-25243. It's no longer needed, because
a routine can no longer be re-parsed in the middle of a statement.

Author: vuvova

sql/sql_class.h

@@ -2468,13 +2468,6 @@ class Sp_caches
     DBUG_ASSERT(sp_package_spec_cache == NULL);
     DBUG_ASSERT(sp_package_body_cache == NULL);
   }
-  void sp_caches_swap(Sp_caches &rhs)
-  {
-    swap_variables(sp_cache*, sp_proc_cache, rhs.sp_proc_cache);
-    swap_variables(sp_cache*, sp_func_cache, rhs.sp_func_cache);
-    swap_variables(sp_cache*, sp_package_spec_cache, rhs.sp_package_spec_cache);
-    swap_variables(sp_cache*, sp_package_body_cache, rhs.sp_package_body_cache);
-  }
   void sp_caches_clear();
   /**
     Clear content of sp related caches.

sql/sql_show.cc

@@ -5285,30 +5285,6 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
   uint table_open_method= tables->table_open_method;
   bool can_deadlock;
   MEM_ROOT tmp_mem_root;
-  /*
-    We're going to open FRM files for tables.
-    In case of VIEWs that contain stored function calls,
-    these stored functions will be parsed and put to the SP cache.
-
-    Suppose we have a view containing a stored function call:
-      CREATE VIEW v1 AS SELECT f1() AS c1;
-    and now we're running:
-      SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_NAME=f1();
-    If a parallel thread invalidates the cache,
-    e.g. by creating or dropping some stored routine,
-    the SELECT query will re-parse f1() when processing "v1"
-    and replace the outdated cached version of f1() to a new one.
-    But the old version of f1() is referenced from the m_sp member
-    of the Item_func_sp instances used in the WHERE condition.
-    We cannot destroy it. To avoid such clashes, let's remember
-    all old routines into a temporary SP cache collection
-    and process tables with a new empty temporary SP cache collection.
-    Then restore to the old SP cache collection at the end.
-  */
-  Sp_caches old_sp_caches;
-
-  old_sp_caches.sp_caches_swap(*thd);
-
   bzero(&tmp_mem_root, sizeof(tmp_mem_root));
 
   /*
@@ -5481,14 +5457,6 @@ int get_all_tables(THD *thd, TABLE_LIST *tables, COND *cond)
 err:
   thd->restore_backup_open_tables_state(&open_tables_state_backup);
   free_root(&tmp_mem_root, 0);
-
-  /*
-    Now restore to the saved SP cache collection
-    and clear the temporary SP cache collection.
-  */
-  old_sp_caches.sp_caches_swap(*thd);
-  old_sp_caches.sp_caches_clear();
-
   DBUG_RETURN(error);
 }