bzr commit into mysql-5.1 branch (Dmitry.Shulga:3622) Bug#12546938

[Dmitry Shulga]

#At file:///Users/shulga/projects/mysql/mysql-5.1-bug12546938/ based on revid:vinay.fisrekar@stripped

 3622 Dmitry Shulga	2011-05-23
      Fixed bug#12546938 (formerly known as 61005) - CREATE IF NOT EXIST EVENT will create
      multiple running events.
      
      A CREATE IF NOT EXIST on an event that currently exists and is enabled will 
      cause multiple instances of the event to run. Disabling the event does not 
      help. If the event is dropped, the event stops running, but when created 
      again, multile instances of the event are still running. The only way to get 
      out of this situation is to restart the server. 
      
      The probles was that Event_db_repository::create_event() didn' return information
      that permits discriminate between situation when event wasn't exist and when made
      attempt to create existed event with keyword IF NOT EXIST. In last case the call to
      method Event_db_repository::create_event() returned OK and information about event
      inserted to queue for executions. So after statement's execution is finished 
      there is two event objects corresponding the event that waiting for exectuion.
      
      The solutuon is to add flag into Event_db_repository::create_event() definition
      that signals that event isn't created because event already exist and
      IF NOT EXISTS clause is specified.
     @ sql/event_db_repository.cc
        Event_db_repository::create_event was modified: set new added argument
        event_already_exists in true value if event wasn't created because event
        already exist and IF NOT EXIST clause was set.
     @ sql/event_db_repository.h
        Added OUT argument 'event_already_exists' into create_event() method.
     @ sql/events.cc
        Events::create_event was modified: insert new element into
        event queue only if event was actually created.

    modified:
      sql/event_db_repository.cc
      sql/event_db_repository.h
      sql/events.cc
=== modified file 'sql/event_db_repository.cc'
--- a/sql/event_db_repository.cc	2011-05-04 12:59:24 +0000
+++ b/sql/event_db_repository.cc	2011-05-23 15:16:04 +0000
@@ -615,7 +615,8 @@ Event_db_repository::open_event_table(TH
 
 bool
 Event_db_repository::create_event(THD *thd, Event_parse_data *parse_data,
-                                  my_bool create_if_not)
+                                  bool create_if_not,
+                                  bool *event_already_exists)
 {
   int ret= 1;
   TABLE *table= NULL;
@@ -648,8 +649,11 @@ Event_db_repository::create_event(THD *t
     }
     else
       my_error(ER_EVENT_ALREADY_EXISTS, MYF(0), parse_data->name.str);
+
+    *event_already_exists= true;
     goto end;
-  }
+  } else
+    *event_already_exists= false;
 
   DBUG_PRINT("info", ("non-existent, go forward"));
 

=== modified file 'sql/event_db_repository.h'
--- a/sql/event_db_repository.h	2007-08-15 15:08:44 +0000
+++ b/sql/event_db_repository.h	2011-05-23 15:16:04 +0000
@@ -73,7 +73,8 @@ public:
   Event_db_repository(){}
 
   bool
-  create_event(THD *thd, Event_parse_data *parse_data, my_bool create_if_not);
+  create_event(THD *thd, Event_parse_data *parse_data, bool create_if_not,
+               bool *event_already_exists);
 
   bool
   update_event(THD *thd, Event_parse_data *parse_data, LEX_STRING *new_dbname,

=== modified file 'sql/events.cc'
--- a/sql/events.cc	2010-03-28 08:37:47 +0000
+++ b/sql/events.cc	2011-05-23 15:16:04 +0000
@@ -370,6 +370,7 @@ create_query_string(THD *thd, String *bu
   return 0;
 }
 
+
 /**
   Create a new event.
 
@@ -391,7 +392,7 @@ Events::create_event(THD *thd, Event_par
                      bool if_not_exists)
 {
   int ret;
-  bool save_binlog_row_based;
+  bool save_binlog_row_based, event_already_exists;
   DBUG_ENTER("Events::create_event");
 
   /*
@@ -440,7 +441,8 @@ Events::create_event(THD *thd, Event_par
   pthread_mutex_lock(&LOCK_event_metadata);
 
   /* On error conditions my_error() is called so no need to handle here */
-  if (!(ret= db_repository->create_event(thd, parse_data, if_not_exists)))
+  if (!(ret= db_repository->create_event(thd, parse_data, if_not_exists,
+                                         &event_already_exists)))
   {
     Event_queue_element *new_element;
     bool dropped= 0;
@@ -460,8 +462,12 @@ Events::create_event(THD *thd, Event_par
     {
       /* TODO: do not ignore the out parameter and a possible OOM error! */
       bool created;
-      if (event_queue)
+
+      if (event_queue && !event_already_exists ||
+          (event_already_exists && !if_not_exists))
         event_queue->create_event(thd, new_element, &created);
+      else
+        delete new_element;
     }
     /*
       binlog the create event unless it's been successfully dropped
@@ -472,16 +478,14 @@ Events::create_event(THD *thd, Event_par
       DBUG_ASSERT(thd->query() && thd->query_length());
       String log_query;
       if (create_query_string(thd, &log_query))
-      {
         sql_print_error("Event Error: An error occurred while creating query string, "
                         "before writing it into binary log.");
-        /* Restore the state of binlog format */
-        thd->current_stmt_binlog_row_based= save_binlog_row_based;
-        DBUG_RETURN(TRUE);
-      }
-      /* If the definer is not set or set to CURRENT_USER, the value of CURRENT_USER 
-         will be written into the binary log as the definer for the SQL thread. */
-      ret= write_bin_log(thd, TRUE, log_query.c_ptr(), log_query.length());
+      else
+        /*
+          If the definer is not set or set to CURRENT_USER, the value of CURRENT_USER
+          will be written into the binary log as the definer for the SQL thread.
+        */
+        ret= write_bin_log(thd, TRUE, log_query.c_ptr(), log_query.length());
     }
   }
   pthread_mutex_unlock(&LOCK_event_metadata);


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