Bug#49534: multitable IGNORE update with sql_safe_updates

error causes debug assertion

The IGNORE option of the multiple-table UPDATE command was
not intended to suppress errors caused by the
sql_safe_updates mode. This flag will raise an error if the
execution of UPDATE does not use a key for row retrieval,
and should continue do so regardless of the IGNORE option.

However the implementation of IGNORE does not support
exceptions to the rule; it always converts errors to
warnings and cannot be extended. The Internal_error_handler
interface offers the infrastructure to handle individual
errors, making sure that the error raised by
sql_safe_updates is not silenced.

Fixed by implementing an Internal_error_handler and using it
for UPDATE IGNORE commands.

1 files changed, 77 insertions, 10 deletions

diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index 32add8679ef..84610630d62 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -1188,6 +1188,56 @@ reopen_tables:
 }
 
 
+/**
+   Implementation of the safe update options during UPDATE IGNORE. This syntax
+   causes an UPDATE statement to ignore all errors. In safe update mode,
+   however, we must never ignore the ER_UPDATE_WITHOUT_KEY_IN_SAFE_MODE. There
+   is a special hook in my_message_sql that will otherwise delete all errors
+   when the IGNORE option is specified. 
+
+   In the future, all IGNORE handling should be used with this class and all
+   traces of the hack outlined below should be removed.
+
+   - The parser detects IGNORE option and sets thd->lex->ignore= 1
+   
+   - In JOIN::optimize, if this is set, then 
+     thd->lex->current_select->no_error gets set.
+
+   - In my_message_sql(), if the flag above is set then any error is
+     unconditionally converted to a warning.
+
+   We are moving in the direction of using Internal_error_handler subclasses
+   to do all such error tweaking, please continue this effort if new bugs
+   appear.
+ */
+class Safe_dml_handler : public Internal_error_handler {
+
+private:
+  bool m_handled_error;
+
+public:
+  explicit Safe_dml_handler() : m_handled_error(FALSE) {}
+
+  bool handle_error(uint sql_errno,
+                    const char *message,
+                    MYSQL_ERROR::enum_warning_level level,
+                    THD *thd)
+  {
+    if (level == MYSQL_ERROR::WARN_LEVEL_ERROR &&
+        sql_errno == ER_UPDATE_WITHOUT_KEY_IN_SAFE_MODE)
+        
+    {      
+      thd->main_da.set_error_status(thd, sql_errno, message);
+      m_handled_error= TRUE;
+      return TRUE;
+    }
+    return FALSE;
+  }
+
+  bool handled_error() { return m_handled_error; }
+
+};
+
 /*
   Setup multi-update handling and call SELECT to do the join
 */
@@ -1216,18 +1266,35 @@ bool mysql_multi_update(THD *thd,
                                MODE_STRICT_ALL_TABLES));
 
   List<Item> total_list;
+
+  Safe_dml_handler handler;
+  bool using_handler= thd->options & OPTION_SAFE_UPDATES;
+  if (using_handler)
+    thd->push_internal_handler(&handler);
+
   res= mysql_select(thd, &select_lex->ref_pointer_array,
-                      table_list, select_lex->with_wild,
-                      total_list,
-                      conds, 0, (ORDER *) NULL, (ORDER *)NULL, (Item *) NULL,
-                      (ORDER *)NULL,
-                      options | SELECT_NO_JOIN_CACHE | SELECT_NO_UNLOCK |
-                      OPTION_SETUP_TABLES_DONE,
-                      result, unit, select_lex);
-  DBUG_PRINT("info",("res: %d  report_error: %d", res,
-                     (int) thd->is_error()));
+                    table_list, select_lex->with_wild,
+                    total_list,
+                    conds, 0, (ORDER *) NULL, (ORDER *)NULL, (Item *) NULL,
+                    (ORDER *)NULL,
+                    options | SELECT_NO_JOIN_CACHE | SELECT_NO_UNLOCK |
+                    OPTION_SETUP_TABLES_DONE,
+                    result, unit, select_lex);
+
+  if (using_handler)
+  {
+    Internal_error_handler *top_handler= thd->pop_internal_handler();
+    DBUG_ASSERT(&handler == top_handler);
+  }
+
+  DBUG_PRINT("info",("res: %d  report_error: %d", res, (int) thd->is_error()));
   res|= thd->is_error();
-  if (unlikely(res))
+  /*
+    Todo: remove below code and make Safe_dml_handler do error processing
+    instead. That way we can return the actual error instead of
+    ER_UNKNOWN_ERROR.
+  */
+  if (unlikely(res) && (!using_handler || !handler.handled_error()))
   {
     /* If we had a another error reported earlier then this will be ignored */
     result->send_error(ER_UNKNOWN_ERROR, ER(ER_UNKNOWN_ERROR));