Merge bk-internal.mysql.com:/home/bk/mysql-5.1-runtime

into  vajra.(none):/opt/local/work/mysql-5.1-c1

1 files changed, 530 insertions, 426 deletions

diff --git a/sql/events.cc b/sql/events.cc
index 46111bcaa91..7c44116af55 100644
--- a/sql/events.cc
+++ b/sql/events.cc
@@ -19,7 +19,6 @@
 #include "event_db_repository.h"
 #include "event_queue.h"
 #include "event_scheduler.h"
-#include "sp_head.h"
 
 /*
  TODO list :
@@ -66,7 +65,7 @@
 static const char *opt_event_scheduler_state_names[]=
     { "OFF", "ON", "0", "1", "DISABLED", NullS };
 
-TYPELIB Events::opt_typelib=
+const TYPELIB Events::opt_typelib=
 {
   array_elements(opt_event_scheduler_state_names)-1,
   "",
@@ -82,7 +81,7 @@ TYPELIB Events::opt_typelib=
 */
 static const char *var_event_scheduler_state_names[]= { "OFF", "ON", NullS };
 
-TYPELIB Events::var_typelib=
+const TYPELIB Events::var_typelib=
 {
   array_elements(var_event_scheduler_state_names)-1,
   "",
@@ -90,20 +89,13 @@ TYPELIB Events::var_typelib=
   NULL
 };
 
-
-static
-Event_queue events_event_queue;
-
-static
-Event_scheduler events_event_scheduler;
-
-
-Event_db_repository events_event_db_repository;
-
-Events Events::singleton;
-
-enum Events::enum_opt_event_scheduler Events::opt_event_scheduler=
-     Events::EVENTS_OFF;
+Event_queue *Events::event_queue;
+Event_scheduler *Events::scheduler;
+Event_db_repository *Events::db_repository;
+enum Events::enum_opt_event_scheduler
+Events::opt_event_scheduler= Events::EVENTS_OFF;
+pthread_mutex_t Events::LOCK_event_metadata;
+bool Events::check_system_tables_error= FALSE;
 
 
 /*
@@ -128,25 +120,89 @@ int sortcmp_lex_string(LEX_STRING s, LEX_STRING t, CHARSET_INFO *cs)
 }
 
 
-/*
-  Accessor for the singleton instance.
+/**
+  @brief Initialize the start up option of the Events scheduler.
 
-  SYNOPSIS
-    Events::get_instance()
+  Do not initialize the scheduler subsystem yet - the initialization
+  is split into steps as it has to fit into the common MySQL
+  initialization framework.
+  No locking as this is called only at start up.
 
-  RETURN VALUE
-    address
+  @param[in,out]  argument  The value of the argument. If this value
+                            is found in the typelib, the argument is
+                            updated.
+
+  @retval TRUE  unknown option value
+  @retval FALSE success
 */
 
-Events *
-Events::get_instance()
+bool
+Events::set_opt_event_scheduler(char *argument)
 {
-  DBUG_ENTER("Events::get_instance");
-  DBUG_RETURN(&singleton);
+  if (argument == NULL)
+    opt_event_scheduler= Events::EVENTS_DISABLED;
+  else
+  {
+    int type;
+    /*
+      type=   1   2      3   4      5
+           (OFF | ON) - (0 | 1) (DISABLE )
+    */
+    const static enum enum_opt_event_scheduler type2state[]=
+    { EVENTS_OFF, EVENTS_ON, EVENTS_OFF, EVENTS_ON, EVENTS_DISABLED };
+
+    type= find_type(argument, &opt_typelib, 1);
+
+    DBUG_ASSERT(type >= 0 && type <= 5); /* guaranteed by find_type */
+
+    if (type == 0)
+    {
+      fprintf(stderr, "Unknown option to event-scheduler: %s\n", argument);
+      return TRUE;
+    }
+    opt_event_scheduler= type2state[type-1];
+  }
+  return FALSE;
 }
 
 
-/*
+/**
+  Return a string representation of the current scheduler mode.
+*/
+
+const char *
+Events::get_opt_event_scheduler_str()
+{
+  const char *str;
+
+  pthread_mutex_lock(&LOCK_event_metadata);
+  str= opt_typelib.type_names[(int) opt_event_scheduler];
+  pthread_mutex_unlock(&LOCK_event_metadata);
+
+  return str;
+}
+
+
+/**
+  Push an error into the error stack if the system tables are
+  not up to date.
+*/
+
+bool Events::check_if_system_tables_error()
+{
+  DBUG_ENTER("Events::check_if_system_tables_error");
+
+  if (check_system_tables_error)
+  {
+    my_error(ER_EVENTS_DB_ERROR, MYF(0));
+    DBUG_RETURN(TRUE);
+  }
+
+  DBUG_RETURN(FALSE);
+}
+
+
+/**
   Reconstructs interval expression from interval type and expression
   value that is in form of a value of the smalles entity:
   For
@@ -278,52 +334,65 @@ common_1_lev_code:
   return 0;
 }
 
-/*
-  Constructor of Events class. It's called when events.o
-  is loaded. Assigning addressed of static variables in this
-  object file.
 
-  SYNOPSIS
-    Events::Events()
+/**
+  Create a new event.
+
+  @param[in,out]  thd            THD
+  @param[in]      parse_data     Event's data from parsing stage
+  @param[in]      if_not_exists  Whether IF NOT EXISTS was
+                                 specified
+  In case there is an event with the same name (db) and
+  IF NOT EXISTS is specified, an warning is put into the stack.
+  @sa Events::drop_event for the notes about locking, pre-locking
+  and Events DDL.
+
+  @retval  FALSE  OK
+  @retval  TRUE   Error (reported)
 */
 
-Events::Events()
+bool
+Events::create_event(THD *thd, Event_parse_data *parse_data,
+                     bool if_not_exists)
 {
-  scheduler=     &events_event_scheduler;
-  event_queue=   &events_event_queue;
-  db_repository= &events_event_db_repository;
-}
+  int ret;
+  DBUG_ENTER("Events::create_event");
 
+  /*
+    Let's commit the transaction first - MySQL manual specifies
+    that a DDL issues an implicit commit, and it doesn't say "successful
+    DDL", so that an implicit commit is a property of any successfully
+    parsed DDL statement.
+  */
+  if (end_active_trans(thd))
+    DBUG_RETURN(TRUE);
 
-/*
-  The function exported to the world for creating of events.
+  if (check_if_system_tables_error())
+    DBUG_RETURN(TRUE);
 
-  SYNOPSIS
-    Events::create_event()
-      thd            [in]  THD
-      parse_data     [in]  Event's data from parsing stage
-      if_not_exists  [in]  Whether IF NOT EXISTS was specified in the DDL
+  /*
+    Perform semantic checks outside of Event_db_repository:
+    once CREATE EVENT is supported in prepared statements, the
+    checks will be moved to PREPARE phase.
+  */
+  if (parse_data->check_parse_data(thd))
+    DBUG_RETURN(TRUE);
 
-  RETURN VALUE
-    FALSE  OK
-    TRUE   Error (Reported)
+  /* At create, one of them must be set */
+  DBUG_ASSERT(parse_data->expression || parse_data->execute_at);
 
-  NOTES
-    In case there is an event with the same name (db) and
-    IF NOT EXISTS is specified, an warning is put into the stack.
-*/
+  if (check_access(thd, EVENT_ACL, parse_data->dbname.str, 0, 0, 0,
+                   is_schema_db(parse_data->dbname.str)))
+    DBUG_RETURN(TRUE);
 
-bool
-Events::create_event(THD *thd, Event_parse_data *parse_data, bool if_not_exists)
-{
-  int ret;
-  DBUG_ENTER("Events::create_event");
-  if (unlikely(check_system_tables_error))
+  if (check_db_dir_existence(parse_data->dbname.str))
   {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
+    my_error(ER_BAD_DB_ERROR, MYF(0));
     DBUG_RETURN(TRUE);
   }
 
+  if (parse_data->do_not_create)
+    DBUG_RETURN(FALSE);
   /* 
     Turn off row binlogging of this statement and use statement-based 
     so that all supporting tables are updated for CREATE EVENT command.
@@ -334,8 +403,7 @@ Events::create_event(THD *thd, Event_parse_data *parse_data, bool if_not_exists)
   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)) &&
-      !parse_data->do_not_create)
+  if (!(ret= db_repository->create_event(thd, parse_data, if_not_exists)))
   {
     Event_queue_element *new_element;
 
@@ -345,12 +413,17 @@ Events::create_event(THD *thd, Event_parse_data *parse_data, bool if_not_exists)
                                                    parse_data->name,
                                                    new_element)))
     {
-      DBUG_ASSERT(ret == OP_LOAD_ERROR);
+      db_repository->drop_event(thd, parse_data->dbname, parse_data->name,
+                                TRUE);
       delete new_element;
     }
-    else /* Binlog the create event. */
+    else
     {
-      event_queue->create_event(thd, new_element);
+      /* TODO: do not ignore the out parameter and a possible OOM error! */
+      bool created;
+      if (event_queue)
+        event_queue->create_event(thd, new_element, &created);
+      /* Binlog the create event. */
       if (mysql_bin_log.is_open() && (thd->query_length > 0))
       {
         thd->clear_error();
@@ -365,37 +438,79 @@ Events::create_event(THD *thd, Event_parse_data *parse_data, bool if_not_exists)
 }
 
 
-/*
-  The function exported to the world for alteration of events.
-
-  SYNOPSIS
-    Events::update_event()
-      thd           [in]  THD
-      parse_data    [in]  Event's data from parsing stage
-      rename_to     [in]  Set in case of RENAME TO.
-
-  RETURN VALUE
-    FALSE  OK
-    TRUE   Error
-
-  NOTES
-    et contains data about dbname and event name.
-    new_name is the new name of the event, if not null this means
-    that RENAME TO was specified in the query
+/**
+  Alter an event.
+
+  @param[in,out] thd         THD
+  @param[in]     parse_data  Event's data from parsing stage
+  @param[in]     new_dbname  A new schema name for the event. Set in the case of
+                             ALTER EVENT RENAME, otherwise is NULL.
+  @param[in]     new_name    A new name for the event. Set in the case of
+                             ALTER EVENT RENAME
+
+  Parameter 'et' contains data about dbname and event name.
+  Parameter 'new_name' is the new name of the event, if not null
+  this means that RENAME TO was specified in the query
+  @sa Events::drop_event for the locking notes.
+
+  @retval  FALSE  OK
+  @retval  TRUE   error (reported)
 */
 
 bool
-Events::update_event(THD *thd, Event_parse_data *parse_data, sp_name *rename_to)
+Events::update_event(THD *thd, Event_parse_data *parse_data,
+                     LEX_STRING *new_dbname, LEX_STRING *new_name)
 {
   int ret;
   Event_queue_element *new_element;
+
   DBUG_ENTER("Events::update_event");
-  LEX_STRING *new_dbname= rename_to ? &rename_to->m_db : NULL;
-  LEX_STRING *new_name= rename_to ? &rename_to->m_name : NULL;
-  if (unlikely(check_system_tables_error))
-  {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
+
+  /*
+    For consistency, implicit COMMIT should be the first thing in the
+    execution chain.
+  */
+  if (end_active_trans(thd))
+    DBUG_RETURN(TRUE);
+
+  if (check_if_system_tables_error())
     DBUG_RETURN(TRUE);
+
+  if (parse_data->check_parse_data(thd) || parse_data->do_not_create)
+    DBUG_RETURN(TRUE);
+
+  if (check_access(thd, EVENT_ACL, parse_data->dbname.str, 0, 0, 0,
+                   is_schema_db(parse_data->dbname.str)))
+    DBUG_RETURN(TRUE);
+
+  if (new_dbname)                               /* It's a rename */
+  {
+    /* Check that the new and the old names differ. */
+    if ( !sortcmp_lex_string(parse_data->dbname, *new_dbname,
+                             system_charset_info) &&
+         !sortcmp_lex_string(parse_data->name, *new_name,
+                             system_charset_info))
+    {
+      my_error(ER_EVENT_SAME_NAME, MYF(0), parse_data->name.str);
+      DBUG_RETURN(TRUE);
+    }
+
+    /*
+      And the user has sufficient privileges to use the target database.
+      Do it before checking whether the database exists: we don't want
+      to tell the user that a database doesn't exist if they can not
+      access it.
+    */
+    if (check_access(thd, EVENT_ACL, new_dbname->str, 0, 0, 0,
+                     is_schema_db(new_dbname->str)))
+      DBUG_RETURN(TRUE);
+
+    /* Check that the target database exists */
+    if (check_db_dir_existence(new_dbname->str))
+    {
+      my_error(ER_BAD_DB_ERROR, MYF(0));
+      DBUG_RETURN(TRUE);
+    }
   }
 
   /* 
@@ -408,7 +523,8 @@ Events::update_event(THD *thd, Event_parse_data *parse_data, sp_name *rename_to)
   pthread_mutex_lock(&LOCK_event_metadata);
 
   /* On error conditions my_error() is called so no need to handle here */
-  if (!(ret= db_repository->update_event(thd, parse_data, new_dbname, new_name)))
+  if (!(ret= db_repository->update_event(thd, parse_data,
+                                         new_dbname, new_name)))
   {
     LEX_STRING dbname= new_dbname ? *new_dbname : parse_data->dbname;
     LEX_STRING name= new_name ? *new_name : parse_data->name;
@@ -421,10 +537,18 @@ Events::update_event(THD *thd, Event_parse_data *parse_data, sp_name *rename_to)
       DBUG_ASSERT(ret == OP_LOAD_ERROR);
       delete new_element;
     }
-    else /* Binlog the alter event. */
+    else
     {
-      event_queue->update_event(thd, parse_data->dbname, parse_data->name,
-                                new_element);
+      /*
+        TODO: check if an update actually has inserted an entry
+        into the queue.
+        If not, and the element is ON COMPLETION NOT PRESERVE, delete
+        it right away.
+      */
+      if (event_queue)
+        event_queue->update_event(thd, parse_data->dbname, parse_data->name,
+                                  new_element);
+      /* Binlog the alter event. */
       if (mysql_bin_log.is_open() && (thd->query_length > 0))
       {
         thd->clear_error();
@@ -439,20 +563,28 @@ Events::update_event(THD *thd, Event_parse_data *parse_data, sp_name *rename_to)
 }
 
 
-/*
+/**
   Drops an event
 
-  SYNOPSIS
-    Events::drop_event()
-      thd             [in]  THD
-      dbname          [in]  Event's schema
-      name            [in]  Event's name
-      if_exists       [in]  When set and the event does not exist =>
-                            warning onto the stack
-
-  RETURN VALUE
-    FALSE  OK
-    TRUE   Error (reported)
+  @param[in,out]  thd        THD
+  @param[in]      dbname     Event's schema
+  @param[in]      name       Event's name
+  @param[in]      if_exists  When this is set and the event does not exist
+                             a warning is pushed into the warning stack.
+                             Otherwise the operation produces an error.
+
+  @note Similarly to DROP PROCEDURE, we do not allow DROP EVENT
+  under LOCK TABLES mode, unless table mysql.event is locked.  To
+  ensure that, we do not reset & backup the open tables state in
+  this function - if in LOCK TABLES or pre-locking mode, this will
+  lead to an error 'Table mysql.event is not locked with LOCK
+  TABLES' unless it _is_ locked. In pre-locked mode there is
+  another barrier - DROP EVENT commits the current transaction,
+  and COMMIT/ROLLBACK is not allowed in stored functions and
+  triggers.
+
+  @retval  FALSE  OK
+  @retval  TRUE   Error (reported)
 */
 
 bool
@@ -460,14 +592,30 @@ Events::drop_event(THD *thd, LEX_STRING dbname, LEX_STRING name, bool if_exists)
 {
   int ret;
   DBUG_ENTER("Events::drop_event");
-  if (unlikely(check_system_tables_error))
-  {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
+
+  /*
+    In MySQL, DDL must always commit: since mysql.* tables are
+    non-transactional, we must modify them outside a transaction
+    to not break atomicity.
+    But the second and more important reason to commit here
+    regardless whether we're actually changing mysql.event table
+    or not is replication: end_active_trans syncs the binary log,
+    and unless we run DDL in it's own transaction it may simply
+    never appear on the slave in case the outside transaction
+    rolls back.
+  */
+  if (end_active_trans(thd))
     DBUG_RETURN(TRUE);
-  }
 
-  /* 
-    Turn off row binlogging of this statement and use statement-based so 
+  if (check_if_system_tables_error())
+    DBUG_RETURN(TRUE);
+
+  if (check_access(thd, EVENT_ACL, dbname.str, 0, 0, 0,
+                   is_schema_db(dbname.str)))
+    DBUG_RETURN(TRUE);
+
+  /*
+    Turn off row binlogging of this statement and use statement-based so
     that all supporting tables are updated for DROP EVENT command.
   */
   if (thd->current_stmt_binlog_row_based)
@@ -477,7 +625,8 @@ Events::drop_event(THD *thd, LEX_STRING dbname, LEX_STRING name, bool if_exists)
   /* On error conditions my_error() is called so no need to handle here */
   if (!(ret= db_repository->drop_event(thd, dbname, name, if_exists)))
   {
-    event_queue->drop_event(thd, dbname, name);
+    if (event_queue)
+      event_queue->drop_event(thd, dbname, name);
     /* Binlog the drop event. */
     if (mysql_bin_log.is_open() && (thd->query_length > 0))
     {
@@ -494,10 +643,12 @@ Events::drop_event(THD *thd, LEX_STRING dbname, LEX_STRING name, bool if_exists)
 /**
   Drops all events from a schema
 
-  SYNOPSIS
-    Events::drop_schema_events()
-      thd  Thread
-      db   ASCIIZ schema name
+  @note We allow to drop all events in a schema even if the
+  scheduler is disabled. This is to not produce any warnings
+  in case of DROP DATABASE and a disabled scheduler.
+
+  @param[in,out]  thd  Thread
+  @param[in]      db   ASCIIZ schema name
 */
 
 void
@@ -507,14 +658,15 @@ Events::drop_schema_events(THD *thd, char *db)
 
   DBUG_ENTER("Events::drop_schema_events");
   DBUG_PRINT("enter", ("dropping events from %s", db));
-  if (unlikely(check_system_tables_error))
-  {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
-    DBUG_VOID_RETURN;
-  }
+
+  /*
+    sic: no check if the scheduler is disabled or system tables
+    are damaged, as intended.
+  */
 
   pthread_mutex_lock(&LOCK_event_metadata);
-  event_queue->drop_schema_events(thd, db_lex);
+  if (event_queue)
+    event_queue->drop_schema_events(thd, db_lex);
   db_repository->drop_schema_events(thd, db_lex);
   pthread_mutex_unlock(&LOCK_event_metadata);
 
@@ -522,115 +674,137 @@ Events::drop_schema_events(THD *thd, char *db)
 }
 
 
-/*
-  SHOW CREATE EVENT
-
-  SYNOPSIS
-    Events::show_create_event()
-      thd   Thread context
-      spn   The name of the event (db, name)
-
-  RETURN VALUE
-    FALSE  OK
-    TRUE   Error during writing to the wire
+/**
+  A helper function to generate SHOW CREATE EVENT output from
+  a named event
 */
 
-bool
-Events::show_create_event(THD *thd, LEX_STRING dbname, LEX_STRING name)
+static bool
+send_show_create_event(THD *thd, Event_timed *et, Protocol *protocol)
 {
-  CHARSET_INFO *scs= system_charset_info;
-  int ret;
-  Event_timed *et= new Event_timed();
+  char show_str_buf[10 * STRING_BUFFER_USUAL_SIZE];
+  String show_str(show_str_buf, sizeof(show_str_buf), system_charset_info);
+  List<Item> field_list;
+  LEX_STRING sql_mode;
+  const String *tz_name;
 
-  DBUG_ENTER("Events::show_create_event");
-  DBUG_PRINT("enter", ("name: %s@%s", dbname.str, name.str));
-  if (unlikely(check_system_tables_error))
-  {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
+  DBUG_ENTER("send_show_create_event");
+
+  show_str.length(0);
+  if (et->get_create_event(thd, &show_str))
     DBUG_RETURN(TRUE);
-  }
 
-  ret= db_repository->load_named_event(thd, dbname, name, et);
+  field_list.push_back(new Item_empty_string("Event", NAME_LEN));
 
-  if (!ret)
-  {
-    Protocol *protocol= thd->protocol;
-    char show_str_buf[10 * STRING_BUFFER_USUAL_SIZE];
-    String show_str(show_str_buf, sizeof(show_str_buf), scs);
-    List<Item> field_list;
-    byte *sql_mode_str;
-    ulong sql_mode_len=0;
+  if (sys_var_thd_sql_mode::symbolic_mode_representation(thd, et->sql_mode,
+                                                         &sql_mode))
+    DBUG_RETURN(TRUE);
 
-    show_str.length(0);
-    show_str.set_charset(system_charset_info);
+  field_list.push_back(new Item_empty_string("sql_mode", sql_mode.length));
 
-    if (et->get_create_event(thd, &show_str))
-      goto err;
+  tz_name= et->time_zone->get_name();
 
-    field_list.push_back(new Item_empty_string("Event", NAME_LEN));
+  field_list.push_back(new Item_empty_string("time_zone",
+                                             tz_name->length()));
 
-    sql_mode_str=
-      sys_var_thd_sql_mode::symbolic_mode_representation(thd, et->sql_mode,
-                                                         &sql_mode_len);
+  field_list.push_back(new Item_empty_string("Create Event",
+                                             show_str.length()));
 
-    field_list.push_back(new Item_empty_string("sql_mode", sql_mode_len));
+  if (protocol->send_fields(&field_list,
+                            Protocol::SEND_NUM_ROWS | Protocol::SEND_EOF))
+    DBUG_RETURN(TRUE);
 
-    const String *tz_name= et->time_zone->get_name();
-    field_list.push_back(new Item_empty_string("time_zone",
-                                               tz_name->length()));
+  protocol->prepare_for_resend();
 
-    field_list.push_back(new Item_empty_string("Create Event",
-                                               show_str.length()));
+  protocol->store(et->name.str, et->name.length, system_charset_info);
+  protocol->store(sql_mode.str, sql_mode.length, system_charset_info);
+  protocol->store(tz_name->ptr(), tz_name->length(), system_charset_info);
+  protocol->store(show_str.c_ptr(), show_str.length(), system_charset_info);
 
-    if (protocol->send_fields(&field_list, Protocol::SEND_NUM_ROWS |
-                                           Protocol::SEND_EOF))
-      goto err;
+  if (protocol->write())
+    DBUG_RETURN(TRUE);
 
-    protocol->prepare_for_resend();
-    protocol->store(et->name.str, et->name.length, scs);
+  send_eof(thd);
 
-    protocol->store((char*) sql_mode_str, sql_mode_len, scs);
+  DBUG_RETURN(FALSE);
+}
 
-    protocol->store((char*) tz_name->ptr(), tz_name->length(), scs);
 
-    protocol->store(show_str.c_ptr(), show_str.length(), scs);
-    ret= protocol->write();
-    send_eof(thd);
-  }
-  delete et;
+/**
+  Implement SHOW CREATE EVENT statement
+
+      thd   Thread context
+      spn   The name of the event (db, name)
+
+  @retval  FALSE  OK
+  @retval  TRUE   error (reported)
+*/
+
+bool
+Events::show_create_event(THD *thd, LEX_STRING dbname, LEX_STRING name)
+{
+  Open_tables_state open_tables_backup;
+  Event_timed et;
+  bool ret;
+
+  DBUG_ENTER("Events::show_create_event");
+  DBUG_PRINT("enter", ("name: %s@%s", dbname.str, name.str));
+
+  if (check_if_system_tables_error())
+    DBUG_RETURN(TRUE);
+
+  if (check_access(thd, EVENT_ACL, dbname.str, 0, 0, 0,
+                   is_schema_db(dbname.str)))
+    DBUG_RETURN(TRUE);
+
+  /*
+    We would like to allow SHOW CREATE EVENT under LOCK TABLES and
+    in pre-locked mode. mysql.event table is marked as a system table.
+    This flag reduces the set of its participation scenarios in LOCK TABLES
+    operation, and therefore an out-of-bound open of this table
+    for reading like the one below (sic, only for reading) is
+    more or less deadlock-free. For additional information about when a
+    deadlock can occur please refer to the description of 'system table'
+    flag.
+  */
+  thd->reset_n_backup_open_tables_state(&open_tables_backup);
+  ret= db_repository->load_named_event(thd, dbname, name, &et);
+  thd->restore_backup_open_tables_state(&open_tables_backup);
+
+  if (!ret)
+    ret= send_show_create_event(thd, &et, thd->protocol);
+
   DBUG_RETURN(ret);
-err:
-  delete et;
-  DBUG_RETURN(TRUE);
 }
 
 
-/*
-  Proxy for Event_db_repository::fill_schema_events.
-  Callback for I_S from sql_show.cc
+/**
+  Check access rights and fill INFORMATION_SCHEMA.events table.
 
-  SYNOPSIS
-    Events::fill_schema_events()
-      thd     Thread context
-      tables  The schema table
+  @param[in,out]  thd     Thread context
+  @param[in]      table   The temporary table to fill.
       cond    Unused
 
-  RETURN VALUE
-    0  OK
-    !0 Error
+  In MySQL INFORMATION_SCHEMA tables are temporary tables that are
+  created and filled on demand. In this function, we fill
+  INFORMATION_SCHEMA.events. It is a callback for I_S module, invoked from
+  sql_show.cc
+
+  @return Has to be integer, as such is the requirement of the I_S API
+  @retval  0  success
+  @retval  1  an error, pushed into the error stack
 */
 
 int
 Events::fill_schema_events(THD *thd, TABLE_LIST *tables, COND * /* cond */)
 {
   char *db= NULL;
+  int ret;
+  Open_tables_state open_tables_backup;
   DBUG_ENTER("Events::fill_schema_events");
-  Events *myself= get_instance();
-  if (unlikely(myself->check_system_tables_error))
-  {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
-    DBUG_RETURN(TRUE);
-  }
+
+  if (check_if_system_tables_error())
+    DBUG_RETURN(1);
 
   /*
     If it's SHOW EVENTS then thd->lex->select_lex.db is guaranteed not to
@@ -644,7 +818,17 @@ Events::fill_schema_events(THD *thd, TABLE_LIST *tables, COND * /* cond */)
       DBUG_RETURN(1);
     db= thd->lex->select_lex.db;
   }
-  DBUG_RETURN(myself->db_repository->fill_schema_events(thd, tables, db));
+  /*
+    Reset and backup of the currently open tables in this thread
+    is a way to allow SELECTs from INFORMATION_SCHEMA.events under
+    LOCK TABLES and in pre-locked mode. See also
+    Events::show_create_event for additional comments.
+  */
+  thd->reset_n_backup_open_tables_state(&open_tables_backup);
+  ret= db_repository->fill_schema_events(thd, tables, db);
+  thd->restore_backup_open_tables_state(&open_tables_backup);
+
+  DBUG_RETURN(ret);
 }
 
 
@@ -663,14 +847,17 @@ Events::fill_schema_events(THD *thd, TABLE_LIST *tables, COND * /* cond */)
 */
 
 bool
-Events::init()
+Events::init(my_bool opt_noacl)
 {
   THD *thd;
   bool res= FALSE;
+
   DBUG_ENTER("Events::init");
 
-  if (opt_event_scheduler == Events::EVENTS_DISABLED)
-    DBUG_RETURN(FALSE);
+  /* Disable the scheduler if running with --skip-grant-tables */
+  if (opt_noacl)
+    opt_event_scheduler= EVENTS_DISABLED;
+
 
   /* We need a temporary THD during boot */
   if (!(thd= new THD()))
@@ -686,30 +873,67 @@ Events::init()
   thd->thread_stack= (char*) &thd;
   thd->store_globals();
 
-  if (check_system_tables(thd))
+  /*
+    We will need Event_db_repository anyway, even if the scheduler is
+    disabled - to perform events DDL.
+  */
+  if (!(db_repository= new Event_db_repository))
   {
-    check_system_tables_error= TRUE;
-    sql_print_error("Event Scheduler: The system tables are damaged. "
-                    "The scheduler subsystem will be unusable during this run.");
+    res= TRUE; /* fatal error: request unireg_abort */
     goto end;
   }
-  check_system_tables_error= FALSE;
 
-  if (event_queue->init_queue(thd) || load_events_from_db(thd))
+  /*
+    Since we allow event DDL even if the scheduler is disabled,
+    check the system tables, as we might need them.
+  */
+  if (Event_db_repository::check_system_tables(thd))
   {
-    sql_print_error("Event Scheduler: Error while loading from disk.");
+    sql_print_error("Event Scheduler: An error occurred when initializing "
+                    "system tables.%s",
+                    opt_event_scheduler == EVENTS_DISABLED ?
+                    "" : " Disabling the Event Scheduler.");
+
+    /* Disable the scheduler since the system tables are not up to date */
+    opt_event_scheduler= EVENTS_DISABLED;
+    check_system_tables_error= TRUE;
     goto end;
   }
 
-  scheduler->init_scheduler(event_queue);
+  /*
+    Was disabled explicitly from the command line, or because we're running
+    with --skip-grant-tables, or because we have no system tables.
+  */
+  if (opt_event_scheduler == Events::EVENTS_DISABLED)
+    goto end;
+
 
   DBUG_ASSERT(opt_event_scheduler == Events::EVENTS_ON ||
               opt_event_scheduler == Events::EVENTS_OFF);
-  if (opt_event_scheduler == Events::EVENTS_ON)
-    res= scheduler->start();
 
-  Event_worker_thread::init(this, db_repository);
+  if (!(event_queue= new Event_queue) ||
+      !(scheduler= new Event_scheduler(event_queue)))
+  {
+    res= TRUE; /* fatal error: request unireg_abort */
+    goto end;
+  }
+
+  if (event_queue->init_queue(thd) || load_events_from_db(thd) ||
+      opt_event_scheduler == EVENTS_ON && scheduler->start())
+  {
+    sql_print_error("Event Scheduler: Error while loading from disk.");
+    res= TRUE; /* fatal error: request unireg_abort */
+    goto end;
+  }
+  Event_worker_thread::init(db_repository);
+
 end:
+  if (res)
+  {
+    delete db_repository;
+    delete event_queue;
+    delete scheduler;
+  }
   delete thd;
   /* Remember that we don't have a THD */
   my_pthread_setspecific_ptr(THR_THD,  NULL);
@@ -732,14 +956,18 @@ void
 Events::deinit()
 {
   DBUG_ENTER("Events::deinit");
-  if (likely(!check_system_tables_error))
-  {
-    scheduler->stop();
-    scheduler->deinit_scheduler();
 
-    event_queue->deinit_queue();
+  if (opt_event_scheduler != EVENTS_DISABLED)
+  {
+    delete scheduler;
+    scheduler= NULL;                            /* safety */
+    delete event_queue;
+    event_queue= NULL;                          /* safety */
   }
 
+  delete db_repository;
+  db_repository= NULL;                          /* safety */
+
   DBUG_VOID_RETURN;
 }
 
@@ -756,8 +984,6 @@ void
 Events::init_mutexes()
 {
   pthread_mutex_init(&LOCK_event_metadata, MY_MUTEX_INIT_FAST);
-  event_queue->init_mutexes();
-  scheduler->init_mutexes();
 }
 
 
@@ -771,8 +997,6 @@ Events::init_mutexes()
 void
 Events::destroy_mutexes()
 {
-  event_queue->deinit_mutexes();
-  scheduler->deinit_mutexes();
   pthread_mutex_destroy(&LOCK_event_metadata);
 }
 
@@ -795,283 +1019,163 @@ Events::dump_internal_status()
   puts("LLA = Last Locked At  LUA = Last Unlocked At");
   puts("WOC = Waiting On Condition  DL = Data Locked");
 
-  scheduler->dump_internal_status();
-  event_queue->dump_internal_status();
+  pthread_mutex_lock(&LOCK_event_metadata);
+  if (opt_event_scheduler == EVENTS_DISABLED)
+    puts("The Event Scheduler is disabled");
+  else
+  {
+    scheduler->dump_internal_status();
+    event_queue->dump_internal_status();
+  }
 
+  pthread_mutex_unlock(&LOCK_event_metadata);
   DBUG_VOID_RETURN;
 }
 
 
 /**
-  Starts execution of events by the scheduler
+  Starts or stops the event scheduler thread.
 
-  SYNOPSIS
-    Events::start_execution_of_events()
-
-  RETURN VALUE
-    FALSE  OK
-    TRUE   Error
+  @retval FALSE success
+  @retval TRUE  error
 */
 
 bool
-Events::start_execution_of_events()
+Events::start_or_stop_event_scheduler(enum_opt_event_scheduler start_or_stop)
 {
-  DBUG_ENTER("Events::start_execution_of_events");
-  if (unlikely(check_system_tables_error))
-  {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
-    DBUG_RETURN(TRUE);
-  }
-  DBUG_RETURN(scheduler->start());
-}
+  bool ret= FALSE;
 
+  DBUG_ENTER("Events::start_or_stop_event_scheduler");
 
-/*
-  Stops execution of events by the scheduler.
-  Already running events will not be stopped. If the user needs
-  them stopped manual intervention is needed.
+  DBUG_ASSERT(start_or_stop == Events::EVENTS_ON ||
+              start_or_stop == Events::EVENTS_OFF);
 
-  SYNOPSIS
-    Events::stop_execution_of_events()
-
-  RETURN VALUE
-    FALSE  OK
-    TRUE   Error
-*/
-
-bool
-Events::stop_execution_of_events()
-{
-  DBUG_ENTER("Events::stop_execution_of_events");
-  if (unlikely(check_system_tables_error))
-  {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
+  /*
+    If the scheduler was disabled because there are no/bad
+    system tables, produce a more meaningful error message
+    than ER_OPTION_PREVENTS_STATEMENT
+  */
+  if (check_if_system_tables_error())
     DBUG_RETURN(TRUE);
-  }
-  DBUG_RETURN(scheduler->stop());
-}
-
-
-/*
-  Checks whether the scheduler is running or not.
-
-  SYNOPSIS
-    Events::is_started()
-
-  RETURN VALUE
-    TRUE   Yes
-    FALSE  No
-*/
-
-bool
-Events::is_execution_of_events_started()
-{
-  DBUG_ENTER("Events::is_execution_of_events_started");
-  if (unlikely(check_system_tables_error))
-  {
-    my_error(ER_EVENTS_DB_ERROR, MYF(0));
-    DBUG_RETURN(FALSE);
-  }
-  DBUG_RETURN(scheduler->is_running());
-}
 
+  pthread_mutex_lock(&LOCK_event_metadata);
 
-
-/*
-  Opens mysql.db and mysql.user and checks whether:
-    1. mysql.db has column Event_priv at column 20 (0 based);
-    2. mysql.user has column Event_priv at column 29 (0 based);
-
-  SYNOPSIS
-    Events::check_system_tables()
-      thd  Thread
-
-  RETURN VALUE
-    FALSE  OK
-    TRUE   Error
-*/
-
-bool
-Events::check_system_tables(THD *thd)
-{
-  TABLE_LIST tables;
-  Open_tables_state backup;
-  bool ret= FALSE;
-
-  DBUG_ENTER("Events::check_system_tables");
-  DBUG_PRINT("enter", ("thd: 0x%lx", (long) thd));
-
-  thd->reset_n_backup_open_tables_state(&backup);
-
-  bzero((char*) &tables, sizeof(tables));
-  tables.db= (char*) "mysql";
-  tables.table_name= tables.alias= (char*) "db";
-  tables.lock_type= TL_READ;
-
-  if ((ret= simple_open_n_lock_tables(thd, &tables)))
+  if (opt_event_scheduler == EVENTS_DISABLED)
   {
-    sql_print_error("Event Scheduler: Cannot open mysql.db");
+    my_error(ER_OPTION_PREVENTS_STATEMENT,
+             MYF(0), "--event-scheduler=DISABLED or --skip-grant-tables");
     ret= TRUE;
+    goto end;
   }
-  ret= table_check_intact(tables.table, MYSQL_DB_FIELD_COUNT,
-                          mysql_db_table_fields, &mysql_db_table_last_check,
-                          ER_CANNOT_LOAD_FROM_TABLE);
-  close_thread_tables(thd);
 
-  bzero((char*) &tables, sizeof(tables));
-  tables.db= (char*) "mysql";
-  tables.table_name= tables.alias= (char*) "user";
-  tables.lock_type= TL_READ;
-
-  if (simple_open_n_lock_tables(thd, &tables))
-  {
-    sql_print_error("Event Scheduler: Cannot open mysql.user");
-    ret= TRUE;
-  }
+  if (start_or_stop == EVENTS_ON)
+    ret= scheduler->start();
   else
+    ret= scheduler->stop();
+
+  if (ret)
   {
-    if (tables.table->s->fields < 29 ||
-        strncmp(tables.table->field[29]->field_name,
-                STRING_WITH_LEN("Event_priv")))
-    {
-      sql_print_error("mysql.user has no `Event_priv` column at position %d",
-                      29);
-      ret= TRUE;
-    }
-    close_thread_tables(thd);
+    my_error(ER_EVENT_SET_VAR_ERROR, MYF(0));
+    goto end;
   }
 
-  thd->restore_backup_open_tables_state(&backup);
+  opt_event_scheduler= start_or_stop;
 
+end:
+  pthread_mutex_unlock(&LOCK_event_metadata);
   DBUG_RETURN(ret);
 }
 
 
-/*
-  Loads all ENABLED events from mysql.event into the prioritized
-  queue. Called during scheduler main thread initialization. Compiles
-  the events. Creates Event_queue_element instances for every ENABLED event
-  from mysql.event.
+/**
+  Loads all ENABLED events from mysql.event into a prioritized
+  queue.
 
-  SYNOPSIS
-    Events::load_events_from_db()
-      thd  Thread context. Used for memory allocation in some cases.
+  This function is called during the server start up. It reads
+  every event, computes the next execution time, and if the event
+  needs execution, adds it to a prioritized queue. Otherwise, if
+  ON COMPLETION DROP is specified, the event is automatically
+  removed from the table.
 
-  RETURN VALUE
-    0  OK
-   !0  Error (EVEX_OPEN_TABLE_FAILED, EVEX_MICROSECOND_UNSUP,
-              EVEX_COMPILE_ERROR) - in all these cases mysql.event was
-              tampered.
+  @param[in,out] thd Thread context. Used for memory allocation in some cases.
 
-  NOTES
-    Reports the error to the console
+  @retval  FALSE  success
+  @retval  TRUE   error, the load is aborted
+
+  @note Reports the error to the console
 */
 
-int
+bool
 Events::load_events_from_db(THD *thd)
 {
   TABLE *table;
   READ_RECORD read_record_info;
-  int ret= -1;
+  bool ret= TRUE;
   uint count= 0;
-  bool clean_the_queue= TRUE;
 
   DBUG_ENTER("Events::load_events_from_db");
   DBUG_PRINT("enter", ("thd: 0x%lx", (long) thd));
 
-  if ((ret= db_repository->open_event_table(thd, TL_READ, &table)))
+  if ((ret= db_repository->open_event_table(thd, TL_WRITE, &table)))
   {
-    sql_print_error("Event Scheduler: Table mysql.event is damaged. Can not open");
-    DBUG_RETURN(EVEX_OPEN_TABLE_FAILED);
+    sql_print_error("Event Scheduler: Failed to open table mysql.event");
+    DBUG_RETURN(TRUE);
   }
 
-  init_read_record(&read_record_info, thd, table ,NULL,1,0);
+  init_read_record(&read_record_info, thd, table, NULL, 0, 1);
   while (!(read_record_info.read_record(&read_record_info)))
   {
     Event_queue_element *et;
+    bool created;
+    bool drop_on_completion;
+
     if (!(et= new Event_queue_element))
-    {
-      DBUG_PRINT("info", ("Out of memory"));
-      break;
-    }
+      goto end;
+
     DBUG_PRINT("info", ("Loading event from row."));
 
-    if ((ret= et->load_from_row(thd, table)))
+    if (et->load_from_row(thd, table))
     {
       sql_print_error("Event Scheduler: "
                       "Error while reading from mysql.event. "
                       "The table is probably corrupted");
-      break;
-    }
-    if (et->status != Event_queue_element::ENABLED)
-    {
-      DBUG_PRINT("info",("%s is disabled",et->name.str));
       delete et;
-      continue;
+      goto end;
     }
+    drop_on_completion= (et->on_completion ==
+                         Event_queue_element::ON_COMPLETION_DROP);
+
 
-    /* let's find when to be executed */
-    if (et->compute_next_execution_time())
+    if (event_queue->create_event(thd, et, &created))
     {
-      sql_print_error("Event Scheduler: Error while computing execution time of %s.%s."
-                      " Skipping", et->dbname.str, et->name.str);
-      continue;
+      /* Out of memory */
+      delete et;
+      goto end;
     }
-
+    if (created)
+      count++;
+    else if (drop_on_completion)
     {
-      Event_job_data temp_job_data;
-      DBUG_PRINT("info", ("Event %s loaded from row. ", et->name.str));
-
-      temp_job_data.load_from_row(thd, table);
-
       /*
-        We load only on scheduler root just to check whether the body
-        compiles.
+        If not created, a stale event - drop if immediately if
+        ON COMPLETION NOT PRESERVE
       */
-      switch (ret= temp_job_data.compile(thd, thd->mem_root)) {
-      case EVEX_MICROSECOND_UNSUP:
-        sql_print_error("Event Scheduler: mysql.event is tampered. MICROSECOND is not "
-                        "supported but found in mysql.event");
-        break;
-      case EVEX_COMPILE_ERROR:
-        sql_print_error("Event Scheduler: Error while compiling %s.%s. Aborting load",
-                        et->dbname.str, et->name.str);
-        break;
-      default:
-        break;
+      int rc= table->file->ha_delete_row(table->record[0]);
+      if (rc)
+      {
+        table->file->print_error(rc, MYF(0));
+        goto end;
       }
-      thd->end_statement();
-      thd->cleanup_after_query();
     }
-    if (ret)
-    {
-      delete et;
-      goto end;
-    }
-
-    DBUG_PRINT("load_events_from_db", ("Adding 0x%lx to the exec list.",
-                                       (long) et));
-    event_queue->create_event(thd, et);
-    count++;
   }
-  clean_the_queue= FALSE;
+  sql_print_information("Event Scheduler: Loaded %d event%s",
+                        count, (count == 1) ? "" : "s");
+  ret= FALSE;
+
 end:
   end_read_record(&read_record_info);
 
-  if (clean_the_queue)
-  {
-    event_queue->empty_queue();
-    ret= -1;
-  }
-  else
-  {
-    ret= 0;
-    sql_print_information("Event Scheduler: Loaded %d event%s",
-                          count, (count == 1)?"":"s");
-  }
-
   close_thread_tables(thd);
 
-  DBUG_PRINT("info", ("Status code %d. Loaded %d event(s)", ret, count));
   DBUG_RETURN(ret);
 }