mariadb/sql/tztime.h
unknown 0ea47f3ed4 BUG#9953: CONVERT_TZ requires mysql.time_zone_name to be locked
The problem was that some facilities (like CONVERT_TZ() function or
server HELP statement) may require implicit access to some tables in
'mysql' database.  This access was done by ordinary means of adding
such tables to the list of tables the query is going to open.
However, if we issued LOCK TABLES before that, we would get "table
was not locked" error trying to open such implicit tables.

The solution is to treat certain tables as MySQL system tables, like
we already do for mysql.proc.  Such tables may be opened for reading
at any moment regardless of any locks in effect.  The cost of this is
that system table may be locked for writing only together with other
system tables, it is disallowed to lock system tables for writing and
have any other lock on any other table.

After this patch the following tables are treated as MySQL system
tables:
  mysql.help_category
  mysql.help_keyword
  mysql.help_relation
  mysql.help_topic
  mysql.proc (it already was)
  mysql.time_zone
  mysql.time_zone_leap_second
  mysql.time_zone_name
  mysql.time_zone_transition
  mysql.time_zone_transition_type

These tables are now opened with open_system_tables_for_read() and
closed with close_system_tables(), or one table may be opened with
open_system_table_for_update() and closed with close_thread_tables()
(the latter is used for mysql.proc table, which is updated as part of
normal MySQL server operation).  These functions may be used when
some tables were opened and locked already.

NOTE: online update of time zone tables is not possible during
replication, because there's no time zone cache flush neither on LOCK
TABLES, nor on FLUSH TABLES, so the master may serve stale time zone
data from cache, while on slave updated data will be loaded from the
time zone tables.


mysql-test/r/help.result:
  Update result.
mysql-test/r/lock.result:
  Update result.
mysql-test/r/sp-error.result:
  Update result.
mysql-test/r/timezone2.result:
  Add result for bug#9953: CONVERT_TZ requires mysql.time_zone_name
  to be locked.
mysql-test/r/view.result:
  Update result: use table t3 rather than utilize MySQL system table.
mysql-test/t/help.test:
  Test that we can use HELP even under LOCK TABLES.
mysql-test/t/lock.test:
  Test LOCK TABLE on system tables.
mysql-test/t/timezone2.test:
  Add test case for bug#9953: CONVERT_TZ requires mysql.time_zone_name
  to be locked.
mysql-test/t/view.test:
  Update test: use table t3 rather that utilize MySQL system table.
sql/handler.h:
  Fix comment for 'count' parameter of check_if_locking_is_allowed().
  Add 'current' and 'system_count' parameters.
sql/item_create.cc:
  We no longer have LEX::add_time_zone_tables_to_query_tables().
sql/item_timefunc.cc:
  We no longer have LEX::time_zone_tables_used, so
  Item_func_convert_tz::fix_fields() became the same as base
  Item_date_func::fix_fields().
  
  my_tz_find() no longer takes table list, but takes THD pointer now.
sql/item_timefunc.h:
  Remove dead field and method.
sql/lock.cc:
  Pass values for 'current' and 'system_count' to
  check_if_locking_is_allowed().
sql/log_event.cc:
  We no longer have my_tz_find_with_opening_tz_tables(), its functions is
  performed by my_tz_find().
sql/mysql_priv.h:
  Add functions to work with MySQL system tables.
sql/set_var.cc:
  my_tz_find() no longer takes table list, but takes THD pointer now.
sql/sp.cc:
  Remove close_proc_table().  Use close_system_tables() instead.
  
  Use open_system_tables_for_read() and open_system_table_for_update().
sql/sp.h:
  Remove close_proc_table() declaration.
sql/sql_base.cc:
  Add implementation of open_system_tables_for_read(),
  close_system_tables(), open_system_table_for_update().
sql/sql_help.cc:
  Operate on MySQL system tables mysql.help_* with
  open_system_tables_for_read() and close_system_tables() to allow the
  usage of HELP statement under LOCK TABLES.
sql/sql_lex.cc:
  Remove LEX::time_zone_tables_used and
  LEX::add_time_zone_tables_to_query_tables() which are no longer used.
sql/sql_lex.h:
  Remove LEX::time_zone_tables_used and
  LEX::add_time_zone_tables_to_query_tables() which are no longer used.
sql/sql_parse.cc:
  Remove references to LEX::time_zone_tables_used and
  my_tz_check_n_skip_implicit_tables() which are no longer used.
sql/sql_show.cc:
  Use close_system_tables() instead of removed close_proc_table().
sql/sql_view.cc:
  LEX::time_zone_tables_used is no longer there.
sql/sql_yacc.yy:
  LEX::add_time_zone_tables_to_query_tables() is no longer there.
sql/table.cc:
  Add more tables that should be treated as MySQL system tables.
sql/share/errmsg.txt:
  Change the error message, as now we allow write-locking of several
  system tables if not mixed with ordinary tables.
sql/tztime.cc:
  Do not add time zone tables to the list of query tables in
  tz_init_table_list().
  
  Remove fake_time_zone_tables_list and my_tz_get_tables_list().
  
  In my_tz_init(), open mysql.time_zone_leap_second with
  simple_open_n_lock_tables(), but pass time zone name to my_tz_find(),
  which will open and close time zone tables as necessary.
  
  In tz_load_from_open_tables() do not call table->use_all_columns(), as
  this was already done in open_system_tables_for_read().
  
  my_tz_find() takes THD pointer instead of table list, and calls
  open_system_tables_for_read() and close_system_tables() as necessary.
  
  Remove my_tz_find_with_opening_tz_tables().
sql/tztime.h:
  Remove declarations of my_tz_get_table_list(),
  my_tz_find_with_opening_tz_tables(), fake_time_zone_tables_list,
  definition of my_tz_check_n_skip_implicit_tables().
  Update prototype for my_tz_find().
storage/csv/ha_tina.cc:
  Add new parameters to check_if_locking_is_allowed().
storage/csv/ha_tina.h:
  Add new parameters to check_if_locking_is_allowed().
storage/myisam/ha_myisam.cc:
  Add new parameters to check_if_locking_is_allowed().  In this
  function we count system tables.  If there are system tables, but
  there are also non-system tables, we report an error.
storage/myisam/ha_myisam.h:
  Add new parameters to check_if_locking_is_allowed().
2007-03-09 13:12:31 +03:00

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/* Copyright (C) 2004 MySQL AB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#ifdef USE_PRAGMA_INTERFACE
#pragma interface /* gcc class interface */
#endif
#if !defined(TESTTIME) && !defined(TZINFO2SQL)
/*
This class represents abstract time zone and provides
basic interface for TIME <-> my_time_t conversion.
Actual time zones which are specified by DB, or via offset
or use system functions are its descendants.
*/
class Time_zone: public Sql_alloc
{
public:
Time_zone() {} /* Remove gcc warning */
/*
Converts local time in broken down TIME representation to
my_time_t (UTC seconds since Epoch) represenation.
Returns 0 in case of error. Sets in_dst_time_gap to true if date provided
falls into spring time-gap (or lefts it untouched otherwise).
*/
virtual my_time_t TIME_to_gmt_sec(const TIME *t,
my_bool *in_dst_time_gap) const = 0;
/*
Converts time in my_time_t representation to local time in
broken down TIME representation.
*/
virtual void gmt_sec_to_TIME(TIME *tmp, my_time_t t) const = 0;
/*
Because of constness of String returned by get_name() time zone name
have to be already zeroended to be able to use String::ptr() instead
of c_ptr().
*/
virtual const String * get_name() const = 0;
/*
We need this only for surpressing warnings, objects of this type are
allocated on MEM_ROOT and should not require destruction.
*/
virtual ~Time_zone() {};
};
extern Time_zone * my_tz_UTC;
extern Time_zone * my_tz_SYSTEM;
extern Time_zone * my_tz_find(THD *thd, const String *name);
extern my_bool my_tz_init(THD *org_thd, const char *default_tzname, my_bool bootstrap);
extern void my_tz_free();
extern my_time_t sec_since_epoch_TIME(TIME *t);
/*
Number of elements in table list produced by my_tz_get_table_list()
(this table list contains tables which are needed for dynamical loading
of time zone descriptions). Actually it is imlementation detail that
should not be used anywhere outside of tztime.h and tztime.cc.
*/
static const int MY_TZ_TABLES_COUNT= 4;
#endif /* !defined(TESTTIME) && !defined(TZINFO2SQL) */