Speedup:

- Don't call update_virtual_fields() if table->vfield is not set
- Don't prealloc memory for in open_tables() as this is very seldom used.


sql/records.cc:
  Don't call update_virtual_fields() if table->vfield is not set
sql/sql_base.cc:
  Don't prealloc memory for in open_tables() as this is very seldom used.
  Don't call update_virtual_fields() if table->vfield is not set
sql/sql_delete.cc:
  Don't call update_virtual_fields() if table->vfield is not set
sql/sql_handler.cc:
  Don't call update_virtual_fields() if table->vfield is not set
sql/sql_join_cache.cc:
  Don't call update_virtual_fields() if table->vfield is not set
  Move some frequent values to local variables
sql/sql_table.cc:
  Don't call update_virtual_fields() if table->vfield is not set
sql/sql_update.cc:
  Don't call update_virtual_fields() if table->vfield is not set
sql/table.cc:
  Assert if update_virtual_fields is called with wrong parameters

sql/records.cc

@@ -401,7 +401,7 @@ int rr_sequential(READ_RECORD *info)
       break;
     }
   }
-  if (!tmp)
+  if (!tmp && info->table->vfield)
     update_virtual_fields(info->thd, info->table);
   return tmp;
 }

sql/sql_base.cc

@@ -4706,7 +4706,7 @@ int open_tables(THD *thd, TABLE_LIST **start, uint *counter, uint flags)
     temporary mem_root for new .frm parsing.
     TODO: variables for size
   */
-  init_sql_alloc(&new_frm_mem, 8024, 8024);
+  init_sql_alloc(&new_frm_mem, 8024, 0);
 
   thd->current_tablenr= 0;
  restart:
@@ -8648,14 +8648,9 @@ fill_record(THD * thd, List<Item> &fields, List<Item> &values,
   }
   /* Update virtual fields*/
   thd->abort_on_warning= FALSE;
-  if (vcol_table)
-  {
-    if (vcol_table->vfield)
-    {
-      if (update_virtual_fields(thd, vcol_table, TRUE))
+  if (vcol_table && vcol_table->vfield &&
+      update_virtual_fields(thd, vcol_table, TRUE))
     goto err;
-    }
-  }
   thd->abort_on_warning= save_abort_on_warning;
   thd->no_errors=        save_no_errors;
   DBUG_RETURN(thd->is_error());

sql/sql_delete.cc

@@ -332,6 +332,7 @@ bool mysql_delete(THD *thd, TABLE_LIST *table_list, COND *conds,
   while (!(error=info.read_record(&info)) && !thd->killed &&
 	 ! thd->is_error())
   {
+    if (table->vfield)
       update_virtual_fields(thd, table);
     thd->examined_row_count++;
     // thd->is_error() is tested to disallow delete row on error

sql/sql_handler.cc

@@ -827,6 +827,7 @@ bool mysql_ha_read(THD *thd, TABLE_LIST *tables,
       goto ok;
     }
     /* Generate values for virtual fields */
+    if (table->vfield)
       update_virtual_fields(thd, table);
     if (cond && !cond->val_int())
       continue;

sql/sql_join_cache.cc

@@ -3344,23 +3344,26 @@ int JOIN_TAB_SCAN::next()
   int skip_rc;
   READ_RECORD *info= &join_tab->read_record;
   SQL_SELECT *select= join_tab->cache_select;
+  TABLE *table= join_tab->table;
+  THD *thd= join->thd;
+
   if (is_first_record)
     is_first_record= FALSE;
   else
     err= info->read_record(info);
-  if (!err)
-    update_virtual_fields(join->thd, join_tab->table);
-  while (!err && select && (skip_rc= select->skip_record(join->thd)) <= 0)
+  if (!err && table->vfield)
+    update_virtual_fields(thd, table);
+  while (!err && select && (skip_rc= select->skip_record(thd)) <= 0)
   {
-    if (join->thd->killed || skip_rc < 0) 
+    if (thd->killed || skip_rc < 0) 
       return 1;
     /* 
       Move to the next record if the last retrieved record does not
       meet the condition pushed to the table join_tab.
     */
     err= info->read_record(info);
-    if (!err)
-      update_virtual_fields(join->thd, join_tab->table);
+    if (!err && table->vfield)
+      update_virtual_fields(thd, table);
   } 
   return err; 
 }
@@ -3874,6 +3877,7 @@ int JOIN_TAB_SCAN_MRR::next()
     */ 
     DBUG_ASSERT(cache->buff <= (uchar *) (*ptr) &&
                 (uchar *) (*ptr) <= cache->end_pos);
+    if (join_tab->table->vfield)
       update_virtual_fields(join->thd, join_tab->table);
   }
   return rc;

sql/sql_table.cc

@@ -8078,6 +8078,7 @@ copy_data_between_tables(THD *thd, TABLE *from,TABLE *to,
       error= 1;
       break;
     }
+    if (from->vfield)
       update_virtual_fields(thd, from);
     thd->row_count++;
     if (++thd->progress.counter >= time_to_report_progress)
@@ -8106,6 +8107,7 @@ copy_data_between_tables(THD *thd, TABLE *from,TABLE *to,
       copy_ptr->do_copy(copy_ptr);
     }
     prev_insert_id= to->file->next_insert_id;
+    if (to->vfield)
       update_virtual_fields(thd, to, TRUE);
     if (thd->is_error())
     {

sql/sql_update.cc

@@ -506,6 +506,7 @@ int mysql_update(THD *thd,
 
       while (!(error=info.read_record(&info)) && !thd->killed)
       {
+        if (table->vfield)
           update_virtual_fields(thd, table);
         thd->examined_row_count++;
 	if (!select || (error= select->skip_record(thd)) > 0)
@@ -621,6 +622,7 @@ int mysql_update(THD *thd,
 
   while (!(error=info.read_record(&info)) && !thd->killed)
   {
+    if (table->vfield)
       update_virtual_fields(thd, table);
     thd->examined_row_count++;
     if (!select || select->skip_record(thd) > 0)

sql/table.cc

@@ -5759,8 +5759,7 @@ int update_virtual_fields(THD *thd, TABLE *table, bool for_write)
   DBUG_ENTER("update_virtual_fields");
   Field **vfield_ptr, *vfield;
   int error __attribute__ ((unused))= 0;
-  if (!table || !table->vfield)
-    DBUG_RETURN(0);
+  DBUG_ASSERT(table && table->vfield);
 
   thd->reset_arena_for_cached_items(table->expr_arena);
   /* Iterate over virtual fields in the table */