Merge bk-internal.mysql.com:/home/bk/mysql-5.0

into  mysql.com:/home/dlenev/src/mysql-5.0-mysqlproc


mysql-test/r/sp-error.result:
  Auto merged
mysql-test/t/sp-error.test:
  Auto merged
sql/mysql_priv.h:
  Auto merged
sql/sp.h:
  Auto merged
sql/sql_base.cc:
  Auto merged
sql/sql_lex.cc:
  Auto merged
sql/sql_lex.h:
  Auto merged
sql/share/errmsg.txt:
  Manual merge.
sql/sp.cc:
  Manual merge.

mysql-test/r/sp-error.result

@@ -286,6 +286,19 @@ ERROR 42000: OUT or INOUT argument 2 for routine test.p is not a variable
 call p(42, @tmp_y, 43)|
 ERROR 42000: OUT or INOUT argument 3 for routine test.p is not a variable
 drop procedure p|
+create procedure p() begin end|
+lock table t1 read|
+call p()|
+unlock tables|
+drop procedure p|
+lock tables t1 read, mysql.proc write|
+ERROR HY000: You can't combine write-locking of system 'mysql.proc' table with other tables
+lock tables mysql.proc write, mysql.user write|
+ERROR HY000: You can't combine write-locking of system 'mysql.proc' table with other tables
+lock tables t1 read, mysql.proc read|
+unlock tables|
+lock tables mysql.proc write|
+unlock tables|
 create procedure bug1965()
 begin
 declare c cursor for select val from t1 order by valname;
@@ -477,7 +490,7 @@ begin
 select * from t1;
 end|
 lock table t1 read|
-call bug9566()|
+alter procedure bug9566 comment 'Some comment'|
 ERROR HY000: Table 'proc' was not locked with LOCK TABLES
 unlock tables|
 drop procedure bug9566|

mysql-test/r/sp-threads.result

@@ -55,3 +55,12 @@ call bug11158();
 unlock tables;
 drop procedure bug11158;
 drop table t1, t2;
+drop function if exists bug11554;
+drop view if exists v1;
+create table t1 (i int);
+create function bug11554 () returns int return 1;
+create view v1 as select bug11554() as f;
+insert into t1 (select f from v1);
+drop function bug11554;
+drop table t1;
+drop view v1;

mysql-test/t/sp-error.test

@@ -386,6 +386,29 @@ call p(42, @tmp_y, 43)|
 drop procedure p|
 
 
+#
+# Let us test that we can access mysql.proc table for routines
+# definitions lookup without locking it explicitly.
+#
+create procedure p() begin end|
+lock table t1 read|
+# This should succeed
+call p()|
+unlock tables|
+drop procedure p|
+# Let us check restrictions which this ability puts on mysql.proc locking.
+--error ER_WRONG_LOCK_OF_SYSTEM_TABLE
+lock tables t1 read, mysql.proc write|
+--error ER_WRONG_LOCK_OF_SYSTEM_TABLE
+lock tables mysql.proc write, mysql.user write|
+# Locking for read should be OK
+lock tables t1 read, mysql.proc read|
+unlock tables|
+# You also should be able lock only mysql.proc for write
+lock tables mysql.proc write|
+unlock tables|
+
+
 #
 # BUG#1965
 #
@@ -676,9 +699,7 @@ create procedure bug6600()
 # BUG#9566: explicit LOCK TABLE and store procedures result in illegal state
 #
 # We should not think that mysql.proc table does not exist if we are unable
-# to open it under LOCK TABLE or in prelocked mode. Probably this test
-# should be removed when Monty will allow access to mysql.proc without
-# locking it.
+# to open it under LOCK TABLE or in prelocked mode.
 #
 --disable_warnings
 drop procedure if exists bug9566|
@@ -688,9 +709,11 @@ begin
   select * from t1;
 end|
 lock table t1 read|
-# This should fail because we forgot to lock mysql.proc table explicitly
+# This should fail since we forgot to lock mysql.proc for writing
+# explicitly, and we can't open mysql.proc for _writing_ if there
+# are locked tables.
 --error 1100
-call bug9566()|
+alter procedure bug9566 comment 'Some comment'|
 unlock tables|
 # This should succeed
 drop procedure bug9566|

mysql-test/t/sp-threads.test

@@ -111,6 +111,25 @@ connection con1root;
 drop procedure bug11158;
 drop table t1, t2;
 
+#
+# BUG#11554: Server crashes on statement indirectly using non-cached function
+#
+--disable_warnings
+drop function if exists bug11554;
+drop view if exists v1;
+--enable_warnings
+create table t1 (i int);
+create function bug11554 () returns int return 1;
+create view v1 as select bug11554() as f;
+connection con2root;
+# This should not crash server
+insert into t1 (select f from v1);
+# Clean-up
+connection con1root;
+drop function bug11554;
+drop table t1;
+drop view v1;
+
 #
 # BUG#NNNN: New bug synopsis
 #

sql/lock.cc

@@ -425,6 +425,19 @@ static MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count,
       tables+=table_ptr[i]->file->lock_count();
       lock_count++;
     }
+    /*
+      To be able to open and lock for reading system tables like 'mysql.proc',
+      when we already have some tables opened and locked, and avoid deadlocks
+      we have to disallow write-locking of these tables with any other tables.
+    */
+    if (table_ptr[i]->s->system_table &&
+        table_ptr[i]->reginfo.lock_type >= TL_WRITE_ALLOW_WRITE &&
+        count != 1)
+    {
+      my_error(ER_WRONG_LOCK_OF_SYSTEM_TABLE, MYF(0), table_ptr[i]->s->db,
+               table_ptr[i]->s->table_name);
+      return 0;
+    }
   }
 
   if (!(sql_lock= (MYSQL_LOCK*)

sql/mysql_priv.h

@@ -735,7 +735,7 @@ bool mysql_truncate(THD *thd, TABLE_LIST *table_list, bool dont_send_ok);
 bool mysql_create_or_drop_trigger(THD *thd, TABLE_LIST *tables, bool create);
 TABLE *open_ltable(THD *thd, TABLE_LIST *table_list, thr_lock_type update);
 TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT* mem,
-		  bool *refresh);
+		  bool *refresh, uint flags);
 TABLE *reopen_name_locked_table(THD* thd, TABLE_LIST* table);
 TABLE *find_locked_table(THD *thd, const char *db,const char *table_name);
 bool reopen_table(TABLE *table,bool locked);

sql/share/errmsg.txt

@@ -5368,3 +5368,5 @@ ER_TOO_BIG_PRECISION 42000 S1009
         eng "Too big precision %d specified for column '%-.64s'. Maximum is %d."
 ER_SCALE_BIGGER_THAN_PRECISION 42000 S1009
         eng "Scale may not be larger than the precision (column '%-.64s')."
+ER_WRONG_LOCK_OF_SYSTEM_TABLE
+        eng "You can't combine write-locking of system '%-.64s.%-.64s' table with other tables"

sql/sp.h

@@ -74,9 +74,6 @@ sp_show_create_function(THD *thd, sp_name *name);
 int
 sp_show_status_function(THD *thd, const char *wild);
 
-bool
-sp_function_exists(THD *thd, sp_name *name);
-
 
 /*
   Procedures for pre-caching of stored routines and building table list

sql/sql_base.cc

@@ -542,10 +542,9 @@ void close_thread_tables(THD *thd, bool lock_in_use, bool skip_derived,
 
 bool close_thread_table(THD *thd, TABLE **table_ptr)
 {
-  DBUG_ENTER("close_thread_table");
-
   bool found_old_table= 0;
   TABLE *table= *table_ptr;
+  DBUG_ENTER("close_thread_table");
   DBUG_ASSERT(table->key_read == 0);
   DBUG_ASSERT(table->file->inited == handler::NONE);
 
@@ -972,18 +971,34 @@ TABLE *reopen_name_locked_table(THD* thd, TABLE_LIST* table_list)
 }
 
 
-/******************************************************************************
-** open a table
-** Uses a cache of open tables to find a table not in use.
-** If refresh is a NULL pointer, then the is no version number checking and
-** the table is not put in the thread-open-list
-** If the return value is NULL and refresh is set then one must close
-** all tables and retry the open
-******************************************************************************/
+/*
+  Open a table.
+
+  SYNOPSIS
+    open_table()
+      thd         Thread context
+      table_list  Open first table in list
+      refresh     Pointer to memory that will be set to 1 if
+                  we need to close all tables and reopen them
+                  If this is a NULL pointer, then the is no version
+                  number checking and the table is not put in the
+                  thread-open-list
+      flags       Bitmap of flags to modify how open works:
+                    MYSQL_LOCK_IGNORE_FLUSH - Open table even if someone
+                    has done a flush or namelock on it.
+
+  IMPLEMENTATION
+    Uses a cache of open tables to find a table not in use.
+
+  RETURN
+    NULL  Open failed.  If refresh is set then one should close
+          all other tables and retry the open
+    #     Success. Pointer to TABLE object for open table.
+*/
 
 
 TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
-		  bool *refresh)
+		  bool *refresh, uint flags)
 {
   reg1	TABLE *table;
   char	key[MAX_DBKEY_LENGTH];
@@ -1096,9 +1111,16 @@ TABLE *open_table(THD *thd, TABLE_LIST *table_list, MEM_ROOT *mem_root,
   {
     if (table->s->version != refresh_version)
     {
+      if (flags & MYSQL_LOCK_IGNORE_FLUSH)
+      {
+        /* Force close at once after usage */
+        thd->version= table->s->version;
+        continue;
+      }
+
       /*
-      ** There is a refresh in progress for this table
-      ** Wait until the table is freed or the thread is killed.
+        There is a refresh in progress for this table
+        Wait until the table is freed or the thread is killed.
       */
       close_old_data_files(thd,thd->open_tables,0,0);
       if (table->in_use != thd)
@@ -1681,6 +1703,15 @@ static int open_unireg_entry(THD *thd, TABLE *entry, const char *db,
   if (error == 5)
     DBUG_RETURN(0);	// we have just opened VIEW
 
+  /*
+    We can't mark all tables in 'mysql' database as system since we don't
+    allow to lock such tables for writing with any other tables (even with
+    other system tables) and some privilege tables need this.
+  */
+  if (!my_strcasecmp(system_charset_info, db, "mysql") &&
+      !my_strcasecmp(system_charset_info, name, "proc"))
+    entry->s->system_table= 1;
+
   if (Table_triggers_list::check_n_load(thd, db, name, entry))
     goto err;
 
@@ -1832,7 +1863,7 @@ int open_tables(THD *thd, TABLE_LIST **start, uint *counter)
     }
     (*counter)++;
     if (!tables->table &&
-	!(tables->table= open_table(thd, tables, &new_frm_mem, &refresh)))
+	!(tables->table= open_table(thd, tables, &new_frm_mem, &refresh, 0)))
     {
       free_root(&new_frm_mem, MYF(MY_KEEP_PREALLOC));
       if (tables->view)
@@ -2003,7 +2034,7 @@ TABLE *open_ltable(THD *thd, TABLE_LIST *table_list, thr_lock_type lock_type)
   thd->current_tablenr= 0;
   /* open_ltable can be used only for BASIC TABLEs */
   table_list->required_type= FRMTYPE_TABLE;
-  while (!(table= open_table(thd, table_list, thd->mem_root, &refresh)) &&
+  while (!(table= open_table(thd, table_list, thd->mem_root, &refresh, 0)) &&
          refresh)
     ;
 

sql/sql_class.cc

@@ -156,6 +156,14 @@ bool foreign_key_prefix(Key *a, Key *b)
 /****************************************************************************
 ** Thread specific functions
 ****************************************************************************/
+
+Open_tables_state::Open_tables_state()
+  :version(refresh_version)
+{
+  reset_open_tables_state();
+}
+
+
 /*
   Pass nominal parameters to Statement constructor only to ensure that
   the destructor works OK in case of error. The main_mem_root will be
@@ -164,6 +172,7 @@ bool foreign_key_prefix(Key *a, Key *b)
 
 THD::THD()
   :Statement(CONVENTIONAL_EXECUTION, 0, ALLOC_ROOT_MIN_BLOCK_SIZE, 0),
+   Open_tables_state(),
    user_time(0), global_read_lock(0), is_fatal_error(0),
    rand_used(0), time_zone_used(0),
    last_insert_id_used(0), insert_id_used(0), clear_next_insert_id(0),
@@ -181,10 +190,8 @@ THD::THD()
   db_length= col_access=0;
   query_error= tmp_table_used= 0;
   next_insert_id=last_insert_id=0;
-  open_tables= temporary_tables= handler_tables= derived_tables= 0;
   hash_clear(&handler_tables_hash);
   tmp_table=0;
-  lock=locked_tables=0;
   used_tables=0;
   cuted_fields= sent_row_count= 0L;
   limit_found_rows= 0;
@@ -230,7 +237,6 @@ THD::THD()
 #ifndef NO_EMBEDDED_ACCESS_CHECKS
   db_access=NO_ACCESS;
 #endif
-  version=refresh_version;			// For boot
   *scramble= '\0';
 
   init();
@@ -259,7 +265,6 @@ THD::THD()
   tablespace_op=FALSE;
   ulong tmp=sql_rnd_with_mutex();
   randominit(&rand, tmp + (ulong) &rand, tmp + (ulong) ::query_id);
-  prelocked_mode= NON_PRELOCKED;
 }
 
 
@@ -1775,3 +1780,40 @@ void THD::set_status_var_init()
 {
   bzero((char*) &status_var, sizeof(status_var));
 }
+
+/****************************************************************************
+  Handling of open and locked tables states.
+
+  This is used when we want to open/lock (and then close) some tables when
+  we already have a set of tables open and locked. We use these methods for
+  access to mysql.proc table to find definitions of stored routines.
+****************************************************************************/
+
+bool THD::push_open_tables_state()
+{
+  Open_tables_state *state;
+  DBUG_ENTER("push_open_table_state");
+  /* Currently we only push things one level */
+  DBUG_ASSERT(open_state_list.elements == 0);
+
+  if (!(state= (Open_tables_state*) alloc(sizeof(*state))))
+    DBUG_RETURN(1);                             // Fatal error is set
+  /* Store state for currently open tables */
+  state->set_open_tables_state(this);
+  if (open_state_list.push_back(state, mem_root))
+    DBUG_RETURN(1);                             // Fatal error is set
+  reset_open_tables_state();
+  DBUG_RETURN(0);
+}
+
+void THD::pop_open_tables_state()
+{
+  Open_tables_state *state;
+  DBUG_ENTER("pop_open_table_state");
+  /* Currently we only push things one level */
+  DBUG_ASSERT(open_state_list.elements == 1);
+
+  state= open_state_list.pop();
+  set_open_tables_state(state);
+  DBUG_VOID_RETURN;
+}

sql/sql_class.h

@@ -932,13 +932,94 @@ enum prelocked_mode_type {NON_PRELOCKED= 0, PRELOCKED= 1,
                           PRELOCKED_UNDER_LOCK_TABLES= 2};
 
 
+/*
+  Class that holds information about tables which were open and locked
+  by the thread. It is also used to save/restore this information in
+  push_open_tables_state()/pop_open_tables_state().
+*/
+
+class Open_tables_state
+{
+public:
+  /*
+    open_tables - list of regular tables in use by this thread
+    temporary_tables - list of temp tables in use by this thread
+    handler_tables - list of tables that were opened with HANDLER OPEN
+     and are still in use by this thread
+  */
+  TABLE *open_tables, *temporary_tables, *handler_tables, *derived_tables;
+  /*
+    During a MySQL session, one can lock tables in two modes: automatic
+    or manual. In automatic mode all necessary tables are locked just before
+    statement execution, and all acquired locks are stored in 'lock'
+    member. Unlocking takes place automatically as well, when the
+    statement ends.
+    Manual mode comes into play when a user issues a 'LOCK TABLES'
+    statement. In this mode the user can only use the locked tables.
+    Trying to use any other tables will give an error. The locked tables are
+    stored in 'locked_tables' member.  Manual locking is described in
+    the 'LOCK_TABLES' chapter of the MySQL manual.
+    See also lock_tables() for details.
+  */
+  MYSQL_LOCK *lock;
+  /*
+    Tables that were locked with explicit or implicit LOCK TABLES.
+    (Implicit LOCK TABLES happens when we are prelocking tables for
+     execution of statement which uses stored routines. See description
+     THD::prelocked_mode for more info.)
+  */
+  MYSQL_LOCK *locked_tables;
+  /*
+    prelocked_mode_type enum and prelocked_mode member are used for
+    indicating whenever "prelocked mode" is on, and what type of
+    "prelocked mode" is it.
+
+    Prelocked mode is used for execution of queries which explicitly
+    or implicitly (via views or triggers) use functions, thus may need
+    some additional tables (mentioned in query table list) for their
+    execution.
+
+    First open_tables() call for such query will analyse all functions
+    used by it and add all additional tables to table its list. It will
+    also mark this query as requiring prelocking. After that lock_tables()
+    will issue implicit LOCK TABLES for the whole table list and change
+    thd::prelocked_mode to non-0. All queries called in functions invoked
+    by the main query will use prelocked tables. Non-0 prelocked_mode
+    will also surpress mentioned analysys in those queries thus saving
+    cycles. Prelocked mode will be turned off once close_thread_tables()
+    for the main query will be called.
+
+    Note: Since not all "tables" present in table list are really locked
+    thd::prelocked_mode does not imply thd::locked_tables.
+  */
+  prelocked_mode_type prelocked_mode;
+  ulong	version;
+  uint current_tablenr;
+
+  Open_tables_state();
+
+  void set_open_tables_state(Open_tables_state *state)
+  {
+    *this= *state;
+  }
+
+  void reset_open_tables_state()
+  {
+    open_tables= temporary_tables= handler_tables= derived_tables= 0;
+    lock= locked_tables= 0;
+    prelocked_mode= NON_PRELOCKED;
+  }
+};
+
+
 /*
   For each client connection we create a separate thread with THD serving as
   a thread/connection descriptor
 */
 
 class THD :public ilink,
-           public Statement
+           public Statement,
+           public Open_tables_state
 {
 public:
 #ifdef EMBEDDED_LIBRARY
@@ -1006,34 +1087,6 @@ class THD :public ilink,
   ulong master_access;			/* Global privileges from mysql.user */
   ulong db_access;			/* Privileges for current db */
 
-  /*
-    open_tables - list of regular tables in use by this thread
-    temporary_tables - list of temp tables in use by this thread
-    handler_tables - list of tables that were opened with HANDLER OPEN
-     and are still in use by this thread
-  */
-  TABLE   *open_tables,*temporary_tables, *handler_tables, *derived_tables;
-  /*
-    During a MySQL session, one can lock tables in two modes: automatic
-    or manual. In automatic mode all necessary tables are locked just before
-    statement execution, and all acquired locks are stored in 'lock'
-    member. Unlocking takes place automatically as well, when the
-    statement ends.
-    Manual mode comes into play when a user issues a 'LOCK TABLES'
-    statement. In this mode the user can only use the locked tables.
-    Trying to use any other tables will give an error. The locked tables are
-    stored in 'locked_tables' member.  Manual locking is described in
-    the 'LOCK_TABLES' chapter of the MySQL manual.
-    See also lock_tables() for details.
-  */
-  MYSQL_LOCK	*lock;				/* Current locks */
-  /*
-    Tables that were locked with explicit or implicit LOCK TABLES.
-    (Implicit LOCK TABLES happens when we are prelocking tables for
-     execution of statement which uses stored routines. See description
-     THD::prelocked_mode for more info.)
-  */
-  MYSQL_LOCK	*locked_tables;
   HASH		handler_tables_hash;
   /*
     One thread can hold up to one named user-level lock. This variable
@@ -1150,6 +1203,7 @@ class THD :public ilink,
   List	     <MYSQL_ERROR> warn_list;
   uint	     warn_count[(uint) MYSQL_ERROR::WARN_LEVEL_END];
   uint	     total_warn_count;
+  List	     <Open_tables_state> open_state_list;
   /*
     Id of current query. Statement can be reused to execute several queries
     query_id is global in context of the whole MySQL server.
@@ -1159,7 +1213,7 @@ class THD :public ilink,
     update auto-updatable fields (like auto_increment and timestamp).
   */
   query_id_t query_id, warn_id;
-  ulong	     version, options, thread_id, col_access;
+  ulong	     options, thread_id, col_access;
 
   /* Statement id is thread-wide. This counter is used to generate ids */
   ulong      statement_id_counter;
@@ -1167,7 +1221,7 @@ class THD :public ilink,
   ulong      row_count;  // Row counter, mainly for errors and warnings
   long	     dbug_thread_id;
   pthread_t  real_id;
-  uint	     current_tablenr,tmp_table,global_read_lock;
+  uint	     tmp_table, global_read_lock;
   uint	     server_status,open_options,system_thread;
   uint32     db_length;
   uint       select_number;             //number of select (used for EXPLAIN)
@@ -1218,31 +1272,6 @@ class THD :public ilink,
     long    long_value;
   } sys_var_tmp;
 
-  /*
-    prelocked_mode_type enum and prelocked_mode member are used for
-    indicating whenever "prelocked mode" is on, and what type of
-    "prelocked mode" is it.
-
-    Prelocked mode is used for execution of queries which explicitly
-    or implicitly (via views or triggers) use functions, thus may need
-    some additional tables (mentioned in query table list) for their
-    execution.
-
-    First open_tables() call for such query will analyse all functions
-    used by it and add all additional tables to table its list. It will
-    also mark this query as requiring prelocking. After that lock_tables()
-    will issue implicit LOCK TABLES for the whole table list and change
-    thd::prelocked_mode to non-0. All queries called in functions invoked
-    by the main query will use prelocked tables. Non-0 prelocked_mode
-    will also surpress mentioned analysys in those queries thus saving
-    cycles. Prelocked mode will be turned off once close_thread_tables()
-    for the main query will be called.
-
-    Note: Since not all "tables" present in table list are really locked
-    thd::relocked_mode does not imply thd::locked_tables.
-  */
-  prelocked_mode_type prelocked_mode;
-
   THD();
   ~THD();
 
@@ -1428,8 +1457,11 @@ class THD :public ilink,
              (variables.sql_mode & MODE_STRICT_ALL_TABLES)));
   }
   void set_status_var_init();
+  bool push_open_tables_state();
+  void pop_open_tables_state();
 };
 
+
 #define tmp_disable_binlog(A)       \
   {ulong tmp_disable_binlog__save_options= (A)->options; \
   (A)->options&= ~OPTION_BIN_LOG

sql/sql_lex.cc

@@ -145,7 +145,7 @@ void lex_start(THD *thd, uchar *buf,uint length)
   lex->found_semicolon= 0;
   lex->safe_to_cache_query= 1;
   lex->time_zone_tables_used= 0;
-  lex->leaf_tables_insert= lex->proc_table= lex->query_tables= 0;
+  lex->leaf_tables_insert= lex->query_tables= 0;
   lex->query_tables_last= &lex->query_tables;
   lex->variables_used= 0;
   lex->select_lex.parent_lex= lex;

sql/sql_lex.h

@@ -719,7 +719,6 @@ typedef struct st_lex
     function)
   */
   TABLE_LIST **query_tables_last;
-  TABLE_LIST *proc_table; /* refer to mysql.proc if it was opened by VIEW */
   /* store original leaf_tables for INSERT SELECT and PS/SP */
   TABLE_LIST *leaf_tables_insert;
 

sql/sql_table.cc

@@ -1760,7 +1760,7 @@ TABLE *create_table_from_items(THD *thd, HA_CREATE_INFO *create_info,
                             create_info, *extra_fields, *keys, 0,
                             select_field_count))
     {
-      if (!(table= open_table(thd, create_table, thd->mem_root, (bool*) 0)))
+      if (!(table= open_table(thd, create_table, thd->mem_root, (bool*)0, 0)))
         quick_rm_table(create_info->db_type, create_table->db,
                        table_case_name(create_info, create_table->table_name));
     }
@@ -3571,7 +3571,7 @@ bool mysql_alter_table(THD *thd,char *new_db, char *new_name,
       bzero((void*) &tbl, sizeof(tbl));
       tbl.db= new_db;
       tbl.table_name= tbl.alias= tmp_name;
-      new_table= open_table(thd, &tbl, thd->mem_root, 0);
+      new_table= open_table(thd, &tbl, thd->mem_root, 0, 0);
     }
     else
     {

sql/table.h

@@ -163,6 +163,13 @@ typedef struct st_table_share
   my_bool crashed;
   my_bool is_view;
   my_bool name_lock, replace_with_name_lock;
+  /*
+    TRUE if this is a system table like 'mysql.proc', which we want to be
+    able to open and lock even when we already have some tables open and
+    locked. To avoid deadlocks we have to put certain restrictions on
+    locking of this table for writing. FALSE - otherwise.
+  */
+  my_bool system_table;
 } TABLE_SHARE;