Bug #29157: UPDATE, changed rows incorrect

Sometimes the number of really updated rows (with changed
column values) cannot be determined at the server level
alone (e.g. if the storage engine does not return enough
column values to verify that). So the only dependable way
in such cases is to let the storage engine return that
information if possible.
Fixed the bug at server level by providing a way for the 
storage engine to return information about wether it 
actually updated the row or the old and the new column 
values are the same. It can do that by returning 
HA_ERR_RECORD_IS_THE_SAME in ha_update_row().
Note that each storage engine may choose not to try to
return this status code, so this behaviour remains 
storage engine specific.

include/my_base.h

@@ -396,7 +396,9 @@ enum ha_base_keytype {
 #define HA_ERR_AUTOINC_READ_FAILED 166   /* Failed to get next autoinc value */
 #define HA_ERR_AUTOINC_ERANGE    167     /* Failed to set row autoinc value */
 #define HA_ERR_GENERIC           168     /* Generic error */
-#define HA_ERR_LAST              168 /*Copy last error nr.*/
+#define HA_ERR_RECORD_IS_THE_SAME 169    /* row not actually updated : 
+                                            new values same as the old values */
+#define HA_ERR_LAST              169 /*Copy last error nr.*/
 /* Add error numbers before HA_ERR_LAST and change it accordingly. */
 #define HA_ERR_ERRORS            (HA_ERR_LAST - HA_ERR_FIRST + 1)
 

sql/log_event.cc

@@ -7171,8 +7171,10 @@ replace_record(THD *thd, TABLE *table,
     {
       error=table->file->ha_update_row(table->record[1],
                                        table->record[0]);
-      if (error)
+      if (error && error != HA_ERR_RECORD_IS_THE_SAME)
         table->file->print_error(error, MYF(0));
+      else
+        error= 0;
       DBUG_RETURN(error);
     }
     else
@@ -7856,6 +7858,8 @@ int Update_rows_log_event::do_exec_row(TABLE *table)
     database into the after image delivered from the master.
   */
   error= table->file->ha_update_row(table->record[1], table->record[0]);
+  if (error == HA_ERR_RECORD_IS_THE_SAME)
+    error= 0;
 
   return error;
 }

sql/sp.cc

@@ -715,8 +715,11 @@ sp_update_routine(THD *thd, int type, sp_name *name, st_sp_chistics *chistics)
       table->field[MYSQL_PROC_FIELD_COMMENT]->store(chistics->comment.str,
 						    chistics->comment.length,
 						    system_charset_info);
-    if ((table->file->ha_update_row(table->record[1],table->record[0])))
+    if ((ret= table->file->ha_update_row(table->record[1],table->record[0])) &&
+        ret != HA_ERR_RECORD_IS_THE_SAME)
       ret= SP_WRITE_ROW_FAILED;
+    else
+      ret= 0;
   }
 
   if (ret == SP_OK)

sql/sql_acl.cc

@@ -1825,7 +1825,8 @@ static bool update_user_table(THD *thd, TABLE *table,
   }
   store_record(table,record[1]);
   table->field[2]->store(new_password, new_password_len, system_charset_info);
-  if ((error=table->file->ha_update_row(table->record[1],table->record[0])))
+  if ((error=table->file->ha_update_row(table->record[1],table->record[0])) &&
+      error != HA_ERR_RECORD_IS_THE_SAME)
   {
     table->file->print_error(error,MYF(0));	/* purecov: deadcode */
     DBUG_RETURN(1);
@@ -2041,13 +2042,19 @@ static int replace_user_table(THD *thd, TABLE *table, const LEX_USER &combo,
       We should NEVER delete from the user table, as a uses can still
       use mysqld even if he doesn't have any privileges in the user table!
     */
-    if (cmp_record(table,record[1]) &&
-	(error=table->file->ha_update_row(table->record[1],table->record[0])))
+    if (cmp_record(table,record[1]))
+    {
+      if ((error=
+           table->file->ha_update_row(table->record[1],table->record[0])) &&
+          error != HA_ERR_RECORD_IS_THE_SAME)
       {						// This should never happen
         table->file->print_error(error,MYF(0));	/* purecov: deadcode */
         error= -1;				/* purecov: deadcode */
         goto end;				/* purecov: deadcode */
       }
+      else
+        error= 0;
+    }
   }
   else if ((error=table->file->ha_write_row(table->record[0]))) // insert
   {						// This should never happen
@@ -2161,7 +2168,8 @@ static int replace_db_table(TABLE *table, const char *db,
     if (rights)
     {
       if ((error= table->file->ha_update_row(table->record[1],
-                                             table->record[0])))
+                                             table->record[0])) &&
+          error != HA_ERR_RECORD_IS_THE_SAME)
 	goto table_error;			/* purecov: deadcode */
     }
     else	/* must have been a revoke of all privileges */
@@ -2543,12 +2551,14 @@ static int replace_column_table(GRANT_TABLE *g_t,
 	error=table->file->ha_update_row(table->record[1],table->record[0]);
       else
 	error=table->file->ha_delete_row(table->record[1]);
-      if (error)
+      if (error && error != HA_ERR_RECORD_IS_THE_SAME)
       {
 	table->file->print_error(error,MYF(0)); /* purecov: inspected */
 	result= -1;				/* purecov: inspected */
 	goto end;				/* purecov: inspected */
       }
+      else
+        error= 0;
       grant_column= column_hash_search(g_t, column->column.ptr(),
                                        column->column.length());
       if (grant_column)				// Should always be true
@@ -2608,7 +2618,8 @@ static int replace_column_table(GRANT_TABLE *g_t,
 	{
 	  int tmp_error;
 	  if ((tmp_error=table->file->ha_update_row(table->record[1],
-						    table->record[0])))
+						    table->record[0])) &&
+              tmp_error != HA_ERR_RECORD_IS_THE_SAME)
 	  {					/* purecov: deadcode */
 	    table->file->print_error(tmp_error,MYF(0)); /* purecov: deadcode */
 	    result= -1;				/* purecov: deadcode */
@@ -2730,7 +2741,9 @@ static int replace_table_table(THD *thd, GRANT_TABLE *grant_table,
   {
     if (store_table_rights || store_col_rights)
     {
-      if ((error=table->file->ha_update_row(table->record[1],table->record[0])))
+      if ((error=table->file->ha_update_row(table->record[1],
+                                            table->record[0])) &&
+          error != HA_ERR_RECORD_IS_THE_SAME)
 	goto table_error;			/* purecov: deadcode */
     }
     else if ((error = table->file->ha_delete_row(table->record[1])))
@@ -2848,7 +2861,9 @@ static int replace_routine_table(THD *thd, GRANT_NAME *grant_name,
   {
     if (store_proc_rights)
     {
-      if ((error=table->file->ha_update_row(table->record[1],table->record[0])))
+      if ((error=table->file->ha_update_row(table->record[1],
+                                            table->record[0])) &&
+          error != HA_ERR_RECORD_IS_THE_SAME)
 	goto table_error;
     }
     else if ((error= table->file->ha_delete_row(table->record[1])))
@@ -4914,8 +4929,12 @@ static int modify_grant_table(TABLE *table, Field *host_field,
                       system_charset_info);
     user_field->store(user_to->user.str, user_to->user.length,
                       system_charset_info);
-    if ((error= table->file->ha_update_row(table->record[1], table->record[0])))
+    if ((error= table->file->ha_update_row(table->record[1], 
+                                           table->record[0])) &&
+        error != HA_ERR_RECORD_IS_THE_SAME)
       table->file->print_error(error, MYF(0));
+    else
+      error= 0;
   }
   else
   {

sql/sql_insert.cc

@@ -1423,7 +1423,8 @@ int write_record(THD *thd, TABLE *table,COPY_INFO *info)
             compare_record(table))
         {
           if ((error=table->file->ha_update_row(table->record[1],
-                                                table->record[0])))
+                                                table->record[0])) &&
+              error != HA_ERR_RECORD_IS_THE_SAME)
           {
             if (info->ignore &&
                 !table->file->is_fatal_error(error, HA_CHECK_DUP_KEY))
@@ -1433,7 +1434,10 @@ int write_record(THD *thd, TABLE *table,COPY_INFO *info)
             goto err;
           }
 
+          if (error != HA_ERR_RECORD_IS_THE_SAME)
             info->updated++;
+          else
+            error= 0;
           /*
             If ON DUP KEY UPDATE updates a row instead of inserting one, it's
             like a regular UPDATE statement: it should not affect the value of a
@@ -1481,9 +1485,13 @@ int write_record(THD *thd, TABLE *table,COPY_INFO *info)
             (!table->triggers || !table->triggers->has_delete_triggers()))
         {
           if ((error=table->file->ha_update_row(table->record[1],
-					        table->record[0])))
+					        table->record[0])) &&
+              error != HA_ERR_RECORD_IS_THE_SAME)
             goto err;
+          if (error != HA_ERR_RECORD_IS_THE_SAME)
             info->deleted++;
+          else
+            error= 0;
           thd->record_first_successful_insert_id_in_cur_stmt(table->file->insert_id_for_cur_row);
           /*
             Since we pretend that we have done insert we should call

sql/sql_servers.cc

@@ -872,11 +872,15 @@ update_server_record(TABLE *table, FOREIGN_SERVER *server)
     /* ok, so we can update since the record exists in the table */
     store_record(table,record[1]);
     store_server_fields(table, server);
-    if ((error=table->file->ha_update_row(table->record[1],table->record[0])))
+    if ((error=table->file->ha_update_row(table->record[1],
+                                          table->record[0])) &&
+        error != HA_ERR_RECORD_IS_THE_SAME)
     {
       DBUG_PRINT("info",("problems with ha_update_row %d", error));
       goto end;
     }
+    else
+      error= 0;
   }
 
 end:

sql/sql_update.cc

@@ -548,9 +548,12 @@ int mysql_update(THD *thd,
 	  error= table->file->ha_update_row(table->record[1],
                                             table->record[0]);
         }
-        if (!error)
+        if (!error || error == HA_ERR_RECORD_IS_THE_SAME)
 	{
+          if (error != HA_ERR_RECORD_IS_THE_SAME)
             updated++;
+          else
+            error= 0;
           thd->no_trans_update.stmt= !transactional_table;
 
           if (table->triggers &&
@@ -1524,7 +1527,8 @@ bool multi_update::send_data(List<Item> &not_used_values)
           main_table->file->extra(HA_EXTRA_PREPARE_FOR_UPDATE);
         }
         if ((error=table->file->ha_update_row(table->record[1],
-                                              table->record[0])))
+                                              table->record[0])) &&
+            error != HA_ERR_RECORD_IS_THE_SAME)
         {
           updated--;
           if (!ignore ||
@@ -1542,6 +1546,11 @@ bool multi_update::send_data(List<Item> &not_used_values)
         }
         else
         {
+          if (error == HA_ERR_RECORD_IS_THE_SAME)
+          {
+            error= 0;
+            updated--;
+          }
           /* non-transactional or transactional table got modified   */
           /* either multi_update class' flag is raised in its branch */
           if (table->file->has_transactions())
@@ -1768,13 +1777,17 @@ int multi_update::do_updates(bool from_send_error)
             goto err;
         }
 	if ((local_error=table->file->ha_update_row(table->record[1],
-						    table->record[0])))
+						    table->record[0])) &&
+            local_error != HA_ERR_RECORD_IS_THE_SAME)
 	{
 	  if (!ignore ||
               table->file->is_fatal_error(local_error, HA_CHECK_DUP_KEY))
 	    goto err;
 	}
+        if (local_error != HA_ERR_RECORD_IS_THE_SAME)
           updated++;
+        else
+          local_error= 0;
 
         if (table->triggers &&
             table->triggers->process_triggers(thd, TRG_EVENT_UPDATE,