Fix for bug #4508 "CONVERT_TZ() function with new time zone as param crashes server".

Instead of trying to open time zone tables during calculation of CONVERT_TZ() function
or setting of @@time_zone variable we should open and lock them with the rest of 
statement's table (so we should add them to global table list) and after that use such 
pre-opened tables for loading info about time zones.

mysql-test/r/timezone2.result

@@ -244,3 +244,10 @@ NULL
 select convert_tz( NULL, 'MET', 'UTC');
 convert_tz( NULL, 'MET', 'UTC')
 NULL
+create table t1 (ts timestamp);
+set timestamp=1000000000;
+insert into t1 (ts) values (now());
+select convert_tz(ts, @@time_zone, 'Japan') from t1;
+convert_tz(ts, @@time_zone, 'Japan')
+2001-09-09 10:46:40
+drop table t1;

mysql-test/t/timezone2.test

@@ -187,3 +187,15 @@ select convert_tz('2003-12-31 04:00:00', 'SomeNotExistingTimeZone', 'UTC');
 select convert_tz('2003-12-31 04:00:00', 'MET', 'SomeNotExistingTimeZone');
 select convert_tz('2003-12-31 04:00:00', 'MET', NULL);
 select convert_tz( NULL, 'MET', 'UTC');
+
+#
+# Test for bug #4508 "CONVERT_TZ() function with new time zone as param
+# crashes server." (Was caused by improperly worked mechanism of time zone
+# dynamical loading).
+#
+create table t1 (ts timestamp);
+set timestamp=1000000000;
+insert into t1 (ts) values (now());
+select convert_tz(ts, @@time_zone, 'Japan') from t1;
+drop table t1;
+

scripts/mysql_create_system_tables.sh

@@ -307,7 +307,8 @@ then
   then
     i_tzn="$i_tzn INSERT INTO time_zone_name (Name, Time_Zone_id) VALUES"
     i_tzn="$i_tzn   ('MET', 1), ('UTC', 2), ('Universal', 2), "
-    i_tzn="$i_tzn   ('Europe/Moscow',3), ('leap/Europe/Moscow',4);"
+    i_tzn="$i_tzn   ('Europe/Moscow',3), ('leap/Europe/Moscow',4), "
+    i_tzn="$i_tzn   ('Japan', 5);"
   fi
 fi
 
@@ -327,7 +328,7 @@ then
   if test "$1" = "test" 
   then
     i_tz="$i_tz INSERT INTO time_zone (Time_zone_id, Use_leap_seconds)" 
-    i_tz="$i_tz   VALUES (1,'N'), (2,'N'), (3,'N'), (4,'Y');"
+    i_tz="$i_tz   VALUES (1,'N'), (2,'N'), (3,'N'), (4,'Y'), (5,'N');"
   fi
 fi
 
@@ -546,7 +547,8 @@ then
     i_tzt="$i_tzt  ,(4, 2045689222, 8) ,(4, 2058390022, 9)"
     i_tzt="$i_tzt  ,(4, 2077138822, 8) ,(4, 2090444422, 9)"
     i_tzt="$i_tzt  ,(4, 2108588422, 8) ,(4, 2121894022, 9)"
-    i_tzt="$i_tzt  ,(4, 2140038022, 8);"
+    i_tzt="$i_tzt  ,(4, 2140038022, 8)"
+    i_tzt="$i_tzt  ,(5, -1009875600, 1);"
   fi
 fi
 
@@ -584,7 +586,8 @@ then
     i_tztt="$i_tztt  ,(4, 4, 10800, 0, 'MSK') ,(4, 5, 14400, 1, 'MSD')"
     i_tztt="$i_tztt  ,(4, 6, 18000, 1, 'MSD') ,(4, 7, 7200, 0, 'EET')"
     i_tztt="$i_tztt  ,(4, 8, 10800, 0, 'MSK') ,(4, 9, 14400, 1, 'MSD')"
-    i_tztt="$i_tztt  ,(4, 10, 10800, 1, 'EEST') ,(4, 11, 7200, 0, 'EET');"
+    i_tztt="$i_tztt  ,(4, 10, 10800, 1, 'EEST') ,(4, 11, 7200, 0, 'EET')"
+    i_tztt="$i_tztt  ,(5, 0, 32400, 0, 'CJT') ,(5, 1, 32400, 0, 'JST');"
   fi
 fi
 

sql/item_create.cc

@@ -89,11 +89,6 @@ Item *create_func_conv(Item* a, Item *b, Item *c)
   return new Item_func_conv(a,b,c);
 }
 
-Item *create_func_convert_tz(Item* a, Item *b, Item *c)
-{
-  return new Item_func_convert_tz(a,b,c);
-}
-
 Item *create_func_cos(Item* a)
 {
   return new Item_func_cos(a);

sql/item_create.h

@@ -31,7 +31,6 @@ Item *create_func_char_length(Item* a);
 Item *create_func_cast(Item *a, Cast_target cast_type, int len, CHARSET_INFO *cs);
 Item *create_func_connection_id(void);
 Item *create_func_conv(Item* a, Item *b, Item *c);
-Item *create_func_convert_tz(Item* a, Item *b, Item *c);
 Item *create_func_cos(Item* a);
 Item *create_func_cot(Item* a);
 Item *create_func_crc32(Item* a);

sql/item_timefunc.cc

@@ -1649,18 +1649,28 @@ bool Item_func_from_unixtime::get_date(TIME *ltime,
 
 void Item_func_convert_tz::fix_length_and_dec()
 {
-  String str;
-  
-  thd= current_thd;
   collation.set(&my_charset_bin);
   decimals= 0;
   max_length= MAX_DATETIME_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
+}
+
+
+bool
+Item_func_convert_tz::fix_fields(THD *thd_arg, TABLE_LIST *tables_arg, Item **ref)
+{
+  String str;
+  if (Item_date_func::fix_fields(thd_arg, tables_arg, ref))
+    return 1;
+
+  tz_tables= thd_arg->lex->time_zone_tables_used;
 
   if (args[1]->const_item())
-    from_tz= my_tz_find(thd, args[1]->val_str(&str));
+    from_tz= my_tz_find(args[1]->val_str(&str), tz_tables);
 
   if (args[2]->const_item())
-    to_tz= my_tz_find(thd, args[2]->val_str(&str));
+    to_tz= my_tz_find(args[2]->val_str(&str), tz_tables);
+
+  return 0;
 }
 
 
@@ -1701,10 +1711,10 @@ bool Item_func_convert_tz::get_date(TIME *ltime,
   String str;
   
   if (!args[1]->const_item())
-    from_tz= my_tz_find(thd, args[1]->val_str(&str));
+    from_tz= my_tz_find(args[1]->val_str(&str), tz_tables);
   
   if (!args[2]->const_item())
-    to_tz= my_tz_find(thd, args[2]->val_str(&str));
+    to_tz= my_tz_find(args[2]->val_str(&str), tz_tables);
   
   if (from_tz==0 || to_tz==0 || get_arg0_date(ltime, 0))
   {

sql/item_timefunc.h

@@ -531,9 +531,22 @@ class Item_func_from_unixtime :public Item_date_func
 */
 class Time_zone;
 
+/*
+  This class represents CONVERT_TZ() function.
+  The important fact about this function that it is handled in special way.
+  When such function is met in expression time_zone system tables are added
+  to global list of tables to open, so later those already opened and locked
+  tables can be used during this function calculation for loading time zone
+  descriptions.
+*/
 class Item_func_convert_tz :public Item_date_func
 {
-  THD *thd;
+  /* Cached pointer to list of pre-opened time zone tables. */
+  TABLE_LIST *tz_tables;
+  /*
+    If time zone parameters are constants we are caching objects that
+    represent them.
+  */
   Time_zone *from_tz, *to_tz;
  public:
   Item_func_convert_tz(Item *a, Item *b, Item *c):
@@ -542,6 +555,7 @@ class Item_func_convert_tz :public Item_date_func
   double val() { return (double) val_int(); }
   String *val_str(String *str);
   const char *func_name() const { return "convert_tz"; }
+  bool fix_fields(THD *, struct st_table_list *, Item **);
   void fix_length_and_dec();
   bool get_date(TIME *res, uint fuzzy_date);
 };

sql/lex.h

@@ -499,7 +499,7 @@ static SYMBOL sql_functions[] = {
   { "CONNECTION_ID",	F_SYM(FUNC_ARG0),0,CREATE_FUNC(create_func_connection_id)},
   { "CONTAINS",		F_SYM(FUNC_ARG2),0,CREATE_FUNC_GEOM(create_func_contains)},
   { "CONV",		F_SYM(FUNC_ARG3),0,CREATE_FUNC(create_func_conv)},
-  { "CONVERT_TZ",	F_SYM(FUNC_ARG3),0,CREATE_FUNC(create_func_convert_tz)},
+  { "CONVERT_TZ",	SYM(CONVERT_TZ_SYM)},
   { "COUNT",		SYM(COUNT_SYM)},
   { "COS",		F_SYM(FUNC_ARG1),0,CREATE_FUNC(create_func_cos)},
   { "COT",		F_SYM(FUNC_ARG1),0,CREATE_FUNC(create_func_cot)},

sql/mysql_priv.h

@@ -500,7 +500,6 @@ int mysql_select(THD *thd, Item ***rref_pointer_array,
 		 select_result *result, SELECT_LEX_UNIT *unit, 
 		 SELECT_LEX *select_lex);
 void free_underlaid_joins(THD *thd, SELECT_LEX *select);
-void fix_tables_pointers(SELECT_LEX *select_lex);
 int mysql_explain_union(THD *thd, SELECT_LEX_UNIT *unit,
 			select_result *result);
 int mysql_explain_select(THD *thd, SELECT_LEX *sl, char const *type,

sql/set_var.cc

@@ -2373,7 +2373,8 @@ bool sys_var_thd_time_zone::check(THD *thd, set_var *var)
   }
 #endif
 
-  if (!(var->save_result.time_zone= my_tz_find(thd, res)))
+  if (!(var->save_result.time_zone=
+          my_tz_find(res, thd->lex->time_zone_tables_used)))
   {
     my_error(ER_UNKNOWN_TIME_ZONE, MYF(0), res ? res->c_ptr() : "NULL");
     return 1;
@@ -2418,7 +2419,8 @@ void sys_var_thd_time_zone::set_default(THD *thd, enum_var_type type)
    if (default_tz_name)
    {
      String str(default_tz_name, &my_charset_latin1);
-     global_system_variables.time_zone= my_tz_find(thd, &str);
+     global_system_variables.time_zone=
+       my_tz_find(&str, thd->lex->time_zone_tables_used);
    }
    else
      global_system_variables.time_zone= my_tz_SYSTEM;

sql/set_var.h

@@ -908,6 +908,7 @@ ulong fix_sql_mode(ulong sql_mode);
 extern sys_var_str sys_charset_system;
 extern sys_var_str sys_init_connect;
 extern sys_var_str sys_init_slave;
+extern sys_var_thd_time_zone sys_time_zone;
 CHARSET_INFO *get_old_charset_by_name(const char *old_name);
 gptr find_named(I_List<NAMED_LIST> *list, const char *name, uint length,
 		NAMED_LIST **found);

sql/sql_base.cc

@@ -1670,7 +1670,22 @@ int open_and_lock_tables(THD *thd, TABLE_LIST *tables)
   uint counter;
   if (open_tables(thd, tables, &counter) || lock_tables(thd, tables, counter))
     DBUG_RETURN(-1);				/* purecov: inspected */
-  fix_tables_pointers(thd->lex->all_selects_list);
+  /*
+    Let us propagate pointers to open tables from global table list
+    to table lists in particular selects if needed.
+  */
+  if (thd->lex->all_selects_list->next_select_in_list() ||
+      thd->lex->time_zone_tables_used)
+  {
+    for (SELECT_LEX *sl= thd->lex->all_selects_list;
+	 sl;
+	 sl= sl->next_select_in_list())
+      for (TABLE_LIST *cursor= (TABLE_LIST *) sl->table_list.first;
+           cursor;
+           cursor=cursor->next)
+        if (cursor->table_list)
+          cursor->table= cursor->table_list->table;
+  }
   DBUG_RETURN(mysql_handle_derived(thd->lex));
 }
 

sql/sql_lex.cc

@@ -22,6 +22,16 @@
 #include <m_ctype.h>
 #include <hash.h>
 
+
+/*
+  Fake table list object, pointer to which is used as special value for
+  st_lex::time_zone_tables_used indicating that we implicitly use time
+  zone tables in this statement but real table list was not yet created.
+  Pointer to it is also returned by my_tz_get_tables_list() as indication
+  of transient error;
+*/
+TABLE_LIST fake_time_zone_tables_list;
+
 /* Macros to look like lex */
 
 #define yyGet()		*(lex->ptr++)
@@ -1292,7 +1302,32 @@ bool st_select_lex_unit::create_total_list(THD *thd_arg, st_lex *lex,
 					   TABLE_LIST **result_arg)
 {
   *result_arg= 0;
-  res= create_total_list_n_last_return(thd_arg, lex, &result_arg);
+  if (!(res= create_total_list_n_last_return(thd_arg, lex, &result_arg)))
+  {
+    /*
+      If time zone tables were used implicitly in statement we should add
+      them to global table list.
+    */
+    if (lex->time_zone_tables_used)
+    {
+      /*
+        Altough we are modifying lex data, it won't raise any problem in
+        case when this lex belongs to some prepared statement or stored
+        procedure: such modification does not change any invariants imposed
+        by requirement to reuse the same lex for multiple executions.
+      */
+      if ((lex->time_zone_tables_used= my_tz_get_table_list(thd)) !=
+          &fake_time_zone_tables_list)
+      {
+        *result_arg= lex->time_zone_tables_used;
+      }
+      else
+      {
+        send_error(thd, 0);
+        res= 1;
+      }
+    }
+  }
   return res;
 }
 

sql/sql_lex.h

@@ -633,6 +633,12 @@ typedef struct st_lex
   bool prepared_stmt_code_is_varref;
   /* Names of user variables holding parameters (in EXECUTE) */
   List<LEX_STRING> prepared_stmt_params; 
+  /*
+    If points to fake_time_zone_tables_list indicates that time zone
+    tables are implicitly used by statement, also is used for holding
+    list of those tables after they are opened.
+  */
+  TABLE_LIST *time_zone_tables_used;
   st_lex() {}
   inline void uncacheable(uint8 cause)
   {
@@ -661,6 +667,7 @@ typedef struct st_lex
 				    TABLE_LIST *local_first);
 } LEX;
 
+extern TABLE_LIST fake_time_zone_tables_list;
 
 void lex_init(void);
 void lex_free(void);

sql/sql_parse.cc

@@ -1897,7 +1897,8 @@ mysql_execute_command(THD *thd)
 #endif
   }
 #endif /* !HAVE_REPLICATION */
-  if (&lex->select_lex != lex->all_selects_list &&
+  if ((&lex->select_lex != lex->all_selects_list ||
+       lex->time_zone_tables_used) &&
       lex->unit.create_total_list(thd, lex, &tables))
     DBUG_VOID_RETURN;
 
@@ -3875,6 +3876,7 @@ mysql_init_query(THD *thd, uchar *buf, uint length)
   lex->lock_option= TL_READ;
   lex->found_colon= 0;
   lex->safe_to_cache_query= 1;
+  lex->time_zone_tables_used= 0;
   lex_start(thd, buf, length);
   thd->select_number= lex->select_lex.select_number= 1;
   thd->free_list= 0;

sql/sql_prepare.cc

@@ -1407,7 +1407,8 @@ static int send_prepare_results(Prepared_statement *stmt, bool text_protocol)
   DBUG_PRINT("enter",("command: %d, param_count: %ld",
                       sql_command, stmt->param_count));
 
-  if (select_lex != lex->all_selects_list &&
+  if ((&lex->select_lex != lex->all_selects_list ||
+       lex->time_zone_tables_used) &&
       lex->unit.create_total_list(thd, lex, &tables))
     DBUG_RETURN(1);
 

sql/sql_select.cc

@@ -213,39 +213,6 @@ int handle_select(THD *thd, LEX *lex, select_result *result)
 }
 
 
-void relink_tables(SELECT_LEX *select_lex)
-{
-  for (TABLE_LIST *cursor= (TABLE_LIST *) select_lex->table_list.first;
-       cursor;
-       cursor=cursor->next)
-    if (cursor->table_list)
-      cursor->table= cursor->table_list->table;
-}
-
-
-void fix_tables_pointers(SELECT_LEX *select_lex)
-{
-  if (select_lex->next_select_in_list())
-  {
-    /* Fix tables 'to-be-unioned-from' list to point at opened tables */
-    for (SELECT_LEX *sl= select_lex;
-	 sl;
-	 sl= sl->next_select_in_list())
-      relink_tables(sl);
-  }
-}
-
-void fix_tables_pointers(SELECT_LEX_UNIT *unit)
-{
-  for (SELECT_LEX *sl= unit->first_select(); sl; sl= sl->next_select())
-  {
-    relink_tables(sl);
-    for (SELECT_LEX_UNIT *un= sl->first_inner_unit(); un; un= un->next_unit())
-      fix_tables_pointers(un);
-  }
-}
-
-
 /*
   Function to setup clauses without sum functions
 */

sql/sql_yacc.yy

@@ -463,6 +463,7 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 %token	CASE_SYM
 %token	CONCAT
 %token	CONCAT_WS
+%token  CONVERT_TZ_SYM
 %token	CURDATE
 %token	CURTIME
 %token	DATABASE
@@ -2825,6 +2826,11 @@ simple_expr:
 	  { $$= new Item_func_concat(* $3); }
 	| CONCAT_WS '(' expr ',' expr_list ')'
 	  { $$= new Item_func_concat_ws($3, *$5); }
+	| CONVERT_TZ_SYM '(' expr ',' expr ',' expr ')'
+	  {
+	    Lex->time_zone_tables_used= &fake_time_zone_tables_list;
+	    $$= new Item_func_convert_tz($3, $5, $7);
+	  }
 	| CURDATE optional_braces
 	  { $$= new Item_func_curdate_local(); Lex->safe_to_cache_query=0; }
 	| CURTIME optional_braces
@@ -5308,6 +5314,12 @@ internal_variable_name:
 	  $$.var= tmp;
 	  $$.base_name.str=0;
 	  $$.base_name.length=0;
+          /*
+            If this is time_zone variable we should open time zone
+            describing tables 
+          */
+          if (tmp == &sys_time_zone)
+	    Lex->time_zone_tables_used= &fake_time_zone_tables_list;
 	}
 	| ident '.' ident
 	  {

sql/tztime.cc

@@ -1359,6 +1359,13 @@ static bool tz_inited= 0;
 static uint tz_leapcnt= 0;
 static LS_INFO *tz_lsis= 0;
 
+/*
+  Shows whenever we have found time zone tables during start-up.
+  Used for avoiding of putting those tables to global table list
+  for queries that use time zone info.
+*/
+static bool time_zone_tables_exist= 1;
+
 
 typedef struct st_tz_names_entry: public Sql_alloc
 {
@@ -1387,6 +1394,68 @@ extern "C" byte* my_offset_tzs_get_key(Time_zone_offset *entry, uint *length,
 }
 
 
+/*
+  Prepare table list with time zone related tables from preallocated array.
+
+  SYNOPSIS
+    tz_init_table_list()
+      tz_tabs - pointer to preallocated array of 4 TABLE_LIST objects.
+
+  DESCRIPTION
+    This function prepares list of TABLE_LIST objects which can be used
+    for opening of time zone tables from preallocated array.
+*/
+
+void
+tz_init_table_list(TABLE_LIST *tz_tabs)
+{
+  bzero(tz_tabs, sizeof(TABLE_LIST) * 4);
+  tz_tabs[0].alias= tz_tabs[0].real_name= (char*)"time_zone_name";
+  tz_tabs[1].alias= tz_tabs[1].real_name= (char*)"time_zone";
+  tz_tabs[2].alias= tz_tabs[2].real_name= (char*)"time_zone_transition_type";
+  tz_tabs[3].alias= tz_tabs[3].real_name= (char*)"time_zone_transition";
+  tz_tabs[0].next= tz_tabs+1;
+  tz_tabs[1].next= tz_tabs+2;
+  tz_tabs[2].next= tz_tabs+3;
+  tz_tabs[0].lock_type= tz_tabs[1].lock_type= tz_tabs[2].lock_type=
+    tz_tabs[3].lock_type= TL_READ;
+  tz_tabs[0].db= tz_tabs[1].db= tz_tabs[2].db= tz_tabs[3].db= (char *)"mysql";
+}
+
+
+/*
+  Create table list with time zone related tables.
+
+  SYNOPSIS
+    my_tz_get_table_list()
+      thd     - current thread object
+
+  DESCRIPTION
+    This function creates list of TABLE_LIST objects allocated in thd's
+    memroot, which can be used for opening of time zone tables.
+
+  RETURN VALUES
+    Returns pointer to first TABLE_LIST object, (could be 0 if time zone
+    tables don't exist) and &fake_time_zone_tables_list in case of error.
+*/
+
+TABLE_LIST *
+my_tz_get_table_list(THD *thd)
+{
+  TABLE_LIST *tz_tabs;
+
+  if (!time_zone_tables_exist)
+    return 0;
+
+  if (!(tz_tabs= (TABLE_LIST *)thd->alloc(sizeof(TABLE_LIST) * 4)))
+    return &fake_time_zone_tables_list;
+
+  tz_init_table_list(tz_tabs);
+
+  return tz_tabs;
+}
+
+
 /*
   Initialize time zone support infrastructure.
 
@@ -1399,13 +1468,13 @@ extern "C" byte* my_offset_tzs_get_key(Time_zone_offset *entry, uint *length,
   DESCRIPTION
     This function will init memory structures needed for time zone support,
     it will register mandatory SYSTEM time zone in them. It will try to open
-    mysql.time_zone_leap_seconds table and and load information which further
-    will be shared among all time zones loaded. It will also try to load
-    information about default time zone. If system tables with time zone
-    descriptions don't exist it won't fail (unless default_tzname is time zone
-    from tables). If bootstrap parameter is true then this routine assumes that
-    we are in bootstrap mode and won't load time zone descriptions unless someone
-    specifies default time zone which is supposedly stored in those tables.
+    mysql.time_zone* tables and load information about default time zone and
+    information which further will be shared among all time zones loaded.
+    If system tables with time zone descriptions don't exist it won't fail
+    (unless default_tzname is time zone from tables). If bootstrap parameter
+    is true then this routine assumes that we are in bootstrap mode and won't
+    load time zone descriptions unless someone specifies default time zone
+    which is supposedly stored in those tables.
     It'll also set default time zone if it is specified.
 
   RETURN VALUES
@@ -1416,14 +1485,13 @@ my_bool
 my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap)
 {
   THD *thd;
-  TABLE_LIST tables;
+  TABLE_LIST *tables= 0;
+  TABLE_LIST tables_buff[5];
   TABLE *table;
-  TABLE *lock_ptr;
-  MYSQL_LOCK *lock;
   TZ_NAMES_ENTRY *tmp_tzname;
   my_bool return_val= 1;
   int res;
-  uint not_used;
+  uint counter;
   DBUG_ENTER("my_tz_init");
 
   /*
@@ -1468,7 +1536,7 @@ my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap)
   if (bootstrap)
   {
     /* If we are in bootstrap mode we should not load time zone tables */
-    return_val= 0;
+    return_val= time_zone_tables_exist= 0;
     goto end_with_setting_default_tz;
   }
 
@@ -1480,28 +1548,25 @@ my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap)
 
   thd->db= my_strdup("mysql",MYF(0));
   thd->db_length= 5;				// Safety
-  bzero((char*) &tables,sizeof(tables));
-  tables.alias= tables.real_name= (char*)"time_zone_leap_second";
-  tables.lock_type= TL_READ;
-  tables.db= thd->db;
-
-  if (open_tables(thd, &tables, &not_used))
-  {
-    sql_print_error("Warning: Can't open time zone table: %s "
+  bzero((char*) &tables_buff, sizeof(TABLE_LIST));
+  tables_buff[0].alias= tables_buff[0].real_name=
+    (char*)"time_zone_leap_second";
+  tables_buff[0].lock_type= TL_READ;
+  tables_buff[0].db= thd->db;
+  tables_buff[0].next= tables_buff + 1;
+  /* Fill TABLE_LIST for rest of the time zone describing tables */
+  tz_init_table_list(tables_buff + 1);
+
+  if (open_tables(thd, tables_buff, &counter) ||
+      lock_tables(thd, tables_buff, counter))
+  {
+    sql_print_error("Warning: Can't open and lock time zone table: %s "
                     "trying to live without them", thd->net.last_error);
     /* We will try emulate that everything is ok */
-    return_val= 0;
+    return_val= time_zone_tables_exist= 0;
     goto end_with_setting_default_tz;
   }
-
-  lock_ptr= tables.table;
-  if (!(lock= mysql_lock_tables(thd, &lock_ptr, 1)))
-  {
-    sql_print_error("Fatal error: Can't lock time zone table: %s",
-		    thd->net.last_error);
-    goto end_with_close;
-  }
-
+  tables= tables_buff + 1;
 
   /*
     Now we are going to load leap seconds descriptions that are shared
@@ -1514,11 +1579,16 @@ my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap)
   {
     sql_print_error("Fatal error: Out of memory while loading "
                     "mysql.time_zone_leap_second table");
-    goto end_with_unlock;
+    goto end_with_close;
   }
 
-  table= tables.table;
-  table->file->ha_index_init(0);
+  table= tables_buff[0].table;
+  /*
+    It is OK to ignore ha_index_init()/ha_index_end() return values since
+    mysql.time_zone* tables are MyISAM and these operations always succeed
+    for MyISAM.
+  */
+  (void)table->file->ha_index_init(0);
   tz_leapcnt= 0;
 
   res= table->file->index_first(table->record[0]);
@@ -1530,7 +1600,7 @@ my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap)
       sql_print_error("Fatal error: While loading mysql.time_zone_leap_second"
                       " table: too much leaps");
       table->file->ha_index_end();
-      goto end_with_unlock;
+      goto end_with_close;
     }
 
     tz_lsis[tz_leapcnt].ls_trans= (my_time_t)table->field[0]->val_int();
@@ -1546,13 +1616,13 @@ my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap)
     res= table->file->index_next(table->record[0]);
   }
 
-  table->file->ha_index_end();
+  (void)table->file->ha_index_end();
 
   if (res != HA_ERR_END_OF_FILE)
   {
     sql_print_error("Fatal error: Error while loading "
                     "mysql.time_zone_leap_second table");
-    goto end_with_unlock;
+    goto end_with_close;
   }
 
   /*
@@ -1562,19 +1632,12 @@ my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap)
   return_val= 0;
 
 
-end_with_unlock:
-  mysql_unlock_tables(thd, lock);
-
-end_with_close:
-  close_thread_tables(thd);
-  thd->version--; /* Force close to free memory */
-
 end_with_setting_default_tz:
-  /* If not an error and have default time zone try to load it */
-  if (!return_val && default_tzname)
+  /* If we have default time zone try to load it */
+  if (default_tzname)
   {
     String tzname(default_tzname, &my_charset_latin1);
-    if (!(global_system_variables.time_zone= my_tz_find(thd, &tzname)))
+    if (!(global_system_variables.time_zone= my_tz_find(&tzname, tables)))
     {
       sql_print_error("Fatal error: Illegal or unknown default time zone '%s'",
                       default_tzname);
@@ -1582,6 +1645,10 @@ end_with_setting_default_tz:
     }
   }
 
+end_with_close:
+  thd->version--; /* Force close to free memory */
+  close_thread_tables(thd);
+
 end_with_cleanup:
 
   /* if there were error free time zone describing structs */
@@ -1625,29 +1692,27 @@ void my_tz_free()
   Load time zone description from system tables.
 
   SYNOPSIS
-    tz_load_from_db()
-      thd            - current thread object
+    tz_load_from_open_tables()
       tz_name   - name of time zone that should be loaded.
+      tz_tables - list of tables from which time zone description
+                  should be loaded
 
   DESCRIPTION
-    This function will try to open system tables describing time zones
-    and to load information about time zone specified. It will also update
-    information in hash used for time zones lookup.
+    This function will try to load information about time zone specified
+    from the list of the already opened and locked tables (first table in
+    tz_tables should be time_zone_name, next time_zone, then
+    time_zone_transition_type and time_zone_transition should be last).
+    It will also update information in hash used for time zones lookup.
 
   RETURN VALUES
     Returns pointer to newly created Time_zone object or 0 in case of error.
 
 */
+
 static Time_zone*
-tz_load_from_db(THD *thd, const String *tz_name)
+tz_load_from_open_tables(const String *tz_name, TABLE_LIST *tz_tables)
 {
-  TABLE_LIST tables[4];
   TABLE *table= 0;
-  TABLE *lock_ptr[4];
-  MYSQL_LOCK *lock;
-  char system_db_name[]= "mysql";
-  char *db_save;
-  uint db_length_save;
   TIME_ZONE_INFO *tz_info;
   TZ_NAMES_ENTRY *tmp_tzname;
   Time_zone *return_val= 0;
@@ -1667,9 +1732,8 @@ tz_load_from_db(THD *thd, const String *tz_name)
 #ifdef ABBR_ARE_USED
   char chars[max(TZ_MAX_CHARS + 1, (2 * (MY_TZNAME_MAX + 1)))];
 #endif
-  uint not_used;
 
-  DBUG_ENTER("tz_load_from_db");
+  DBUG_ENTER("tz_load_from_open_tables");
 
 
   /* Prepare tz_info for loading also let us make copy of time zone name */
@@ -1689,77 +1753,46 @@ tz_load_from_db(THD *thd, const String *tz_name)
   */
   strmake(tz_name_buff, tz_name->ptr(), tz_name->length());
 
-  /*
-     Open and lock time zone description tables
-  */
-  db_save= thd->db;
-  db_length_save= thd->db_length;
-  thd->db= system_db_name;
-  thd->db_length= 5;
-
-  bzero((char*) &tables,sizeof(tables));
-  tables[0].alias= tables[0].real_name= (char*)"time_zone_name";
-  tables[1].alias= tables[1].real_name= (char*)"time_zone";
-  tables[2].alias= tables[2].real_name= (char*)"time_zone_transition";
-  tables[3].alias= tables[3].real_name= (char*)"time_zone_transition_type";
-  tables[0].next= tables+1;
-  tables[1].next= tables+2;
-  tables[2].next= tables+3;
-  tables[0].lock_type= tables[1].lock_type= tables[2].lock_type=
-                       tables[3].lock_type= TL_READ;
-  tables[0].db= tables[1].db= tables[2].db= tables[3].db= thd->db;
-  if (open_tables(thd, tables, &not_used))
-  {
-    sql_print_error("Error: Can't open time zone tables: %s",
-                    thd->net.last_error);
-    goto end;
-  }
-
-  lock_ptr[0]= tables[0].table;
-  lock_ptr[1]= tables[1].table;
-  lock_ptr[2]= tables[2].table;
-  lock_ptr[3]= tables[3].table;
-  if (!(lock= mysql_lock_tables(thd, lock_ptr, 4)))
-  {
-    sql_print_error("Error: Can't lock time zone tables: %s",
-                    thd->net.last_error);
-    goto end_with_close;
-  }
-
   /*
     Let us find out time zone id by its name (there is only one index
     and it is specifically for this purpose).
   */
-  table= tables[0].table;
-
+  table= tz_tables->table; 
+  tz_tables= tz_tables->next;
   table->field[0]->store(tz_name->ptr(), tz_name->length(), &my_charset_latin1);
-  table->file->ha_index_init(0);
+  /*
+    It is OK to ignore ha_index_init()/ha_index_end() return values since
+    mysql.time_zone* tables are MyISAM and these operations always succeed
+    for MyISAM.
+  */
+  (void)table->file->ha_index_init(0);
 
   if (table->file->index_read(table->record[0], (byte*)table->field[0]->ptr,
                               0, HA_READ_KEY_EXACT))
   {
     sql_print_error("Error: Can't find description of time zone.");
-    goto end_with_unlock;
+    goto end;
   }
 
   tzid= (uint)table->field[1]->val_int();
 
-  table->file->ha_index_end();
+  (void)table->file->ha_index_end();
 
   /*
     Now we need to lookup record in mysql.time_zone table in order to
     understand whenever this timezone uses leap seconds (again we are
     using the only index in this table).
   */
-  table= tables[1].table;
+  table= tz_tables->table; 
+  tz_tables= tz_tables->next;
   table->field[0]->store((longlong)tzid);
-  table->file->ha_index_init(0);
+  (void)table->file->ha_index_init(0);
 
   if (table->file->index_read(table->record[0], (byte*)table->field[0]->ptr,
                               0, HA_READ_KEY_EXACT))
   {
     sql_print_error("Error: Can't find description of time zone.");
-    goto end_with_unlock;
+    goto end;
   }
 
   /* If Uses_leap_seconds == 'Y' */
@@ -1769,7 +1802,7 @@ tz_load_from_db(THD *thd, const String *tz_name)
     tz_info->lsis= tz_lsis;
   }
 
-  table->file->ha_index_end();
+  (void)table->file->ha_index_end();
 
   /*
     Now we will iterate through records for out time zone in
@@ -1777,9 +1810,10 @@ tz_load_from_db(THD *thd, const String *tz_name)
     only for our time zone guess what are we doing?
     Right - using special index.
   */
-  table= tables[3].table;
+  table= tz_tables->table; 
+  tz_tables= tz_tables->next;
   table->field[0]->store((longlong)tzid);
-  table->file->ha_index_init(0);
+  (void)table->file->ha_index_init(0);
 
   // FIXME Is there any better approach than explicitly specifying 4 ???
   res= table->file->index_read(table->record[0], (byte*)table->field[0]->ptr,
@@ -1793,7 +1827,7 @@ tz_load_from_db(THD *thd, const String *tz_name)
       sql_print_error("Error while loading time zone description from "
                       "mysql.time_zone_transition_type table: too big "
                       "transition type id");
-      goto end_with_unlock;
+      goto end;
     }
 
     ttis[ttid].tt_gmtoff= (long)table->field[2]->val_int();
@@ -1807,7 +1841,7 @@ tz_load_from_db(THD *thd, const String *tz_name)
       sql_print_error("Error while loading time zone description from "
                       "mysql.time_zone_transition_type table: not enough "
                       "room for abbreviations");
-      goto end_with_unlock;
+      goto end;
     }
     ttis[ttid].tt_abbrind= tz_info->charcnt;
     memcpy(chars + tz_info->charcnt, abbr.ptr(), abbr.length());
@@ -1838,10 +1872,10 @@ tz_load_from_db(THD *thd, const String *tz_name)
   {
     sql_print_error("Error while loading time zone description from "
                     "mysql.time_zone_transition_type table");
-    goto end_with_unlock;
+    goto end;
   }
 
-  table->file->ha_index_end();
+  (void)table->file->ha_index_end();
 
 
   /*
@@ -1849,9 +1883,9 @@ tz_load_from_db(THD *thd, const String *tz_name)
     mysql.time_zone_transition table. Here we additionaly need records
     in ascending order by index scan also satisfies us.
   */
-  table= tables[2].table;
+  table= tz_tables->table; 
   table->field[0]->store((longlong)tzid);
-  table->file->ha_index_init(0);
+  (void)table->file->ha_index_init(0);
 
   // FIXME Is there any better approach than explicitly specifying 4 ???
   res= table->file->index_read(table->record[0], (byte*)table->field[0]->ptr,
@@ -1866,14 +1900,14 @@ tz_load_from_db(THD *thd, const String *tz_name)
       sql_print_error("Error while loading time zone description from "
                       "mysql.time_zone_transition table: "
                       "too much transitions");
-      goto end_with_unlock;
+      goto end;
     }
     if (ttid + 1 > tz_info->typecnt)
     {
       sql_print_error("Error while loading time zone description from "
                       "mysql.time_zone_transition table: "
                       "bad transition type id");
-      goto end_with_unlock;
+      goto end;
     }
 
     ats[tz_info->timecnt]= ttime;
@@ -1896,10 +1930,10 @@ tz_load_from_db(THD *thd, const String *tz_name)
   {
     sql_print_error("Error while loading time zone description from "
                     "mysql.time_zone_transition table");
-    goto end_with_unlock;
+    goto end;
   }
 
-  table->file->ha_index_end();
+  (void)table->file->ha_index_end();
   table= 0;
 
   /*
@@ -1916,7 +1950,7 @@ tz_load_from_db(THD *thd, const String *tz_name)
   {
     sql_print_error("Error: Out of memory while loading time zone "
                     "description");
-    goto end_with_unlock;
+    goto end;
   }
 
 
@@ -1941,12 +1975,12 @@ tz_load_from_db(THD *thd, const String *tz_name)
   if (tz_info->typecnt < 1)
   {
     sql_print_error("Error: loading time zone without transition types");
-    goto end_with_unlock;
+    goto end;
   }
   if (prepare_tz_info(tz_info, &tz_storage))
   {
     sql_print_error("Error: Unable to build mktime map for time zone");
-    goto end_with_unlock;
+    goto end;
   }
 
 
@@ -1958,7 +1992,7 @@ tz_load_from_db(THD *thd, const String *tz_name)
        my_hash_insert(&tz_names, (const byte *)tmp_tzname)))
   {
     sql_print_error("Error: Out of memory while loading time zone");
-    goto end_with_unlock;
+    goto end;
   }
 
   /*
@@ -1966,19 +2000,11 @@ tz_load_from_db(THD *thd, const String *tz_name)
   */
   return_val= tmp_tzname->tz;
 
-end_with_unlock:
+end:
 
   if (table)
-    table->file->ha_index_end();
-
-  mysql_unlock_tables(thd, lock);
+    (void)table->file->ha_index_end();
 
-end_with_close:
-  close_thread_tables(thd);
-
-end:
-  thd->db= db_save;
-  thd->db_length= db_length_save;
   DBUG_RETURN(return_val);
 }
 
@@ -2068,8 +2094,8 @@ str_to_offset(const char *str, uint length, long *offset)
 
   SYNOPSIS
     my_tz_find()
-      thd  - current thread
       name - time zone specification
+      tz_tables - list of opened'n'locked time zone describing tables
 
   DESCRIPTION
     This function checks if name is one of time zones described in db,
@@ -2091,7 +2117,11 @@ str_to_offset(const char *str, uint length, long *offset)
     values as parameter without additional external check and this property
     is used by @@time_zone variable handling code).
 
-    It will perform lookup in system tables (mysql.time_zone*) if needed.
+    It will perform lookup in system tables (mysql.time_zone*) if needed
+    using tz_tables as list of already opened tables (for info about this
+    list look at tz_load_from_open_tables() description). It won't perform
+    such lookup if no time zone describing tables were found during server
+    start up.
 
   RETURN VALUE
     Pointer to corresponding Time_zone object. 0 - in case of bad time zone
@@ -2099,7 +2129,7 @@ str_to_offset(const char *str, uint length, long *offset)
 
 */
 Time_zone *
-my_tz_find(THD *thd, const String * name)
+my_tz_find(const String * name, TABLE_LIST *tz_tables)
 {
   TZ_NAMES_ENTRY *tmp_tzname;
   Time_zone *result_tz= 0;
@@ -2109,6 +2139,8 @@ my_tz_find(THD *thd, const String * name)
   DBUG_PRINT("enter", ("time zone name='%s'",
                       name ? ((String *)name)->c_ptr() : "NULL"));
 
+  DBUG_ASSERT(!time_zone_tables_exist || tz_tables);
+
   if (!name)
     DBUG_RETURN(0);
 
@@ -2136,8 +2168,10 @@ my_tz_find(THD *thd, const String * name)
                                                    (const byte *)name->ptr(),
                                                    name->length())))
       result_tz= tmp_tzname->tz;
+    else if(time_zone_tables_exist)
+      result_tz= tz_load_from_open_tables(name, tz_tables);
     else
-      result_tz= tz_load_from_db(thd, name);
+      result_tz= 0;
   }
 
   VOID(pthread_mutex_unlock(&tz_LOCK));

sql/tztime.h

@@ -59,7 +59,8 @@ public:
 
 extern Time_zone * my_tz_UTC;
 extern Time_zone * my_tz_SYSTEM;
-extern Time_zone * my_tz_find(THD *thd, const String *name);
+extern TABLE_LIST * my_tz_get_table_list(THD *thd);
+extern Time_zone * my_tz_find(const String *name, TABLE_LIST *tz_tables);
 extern my_bool     my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap);
 extern void        my_tz_free();