MDEV-4011 Added per thread memory counting and usage

Base code and idea from a patch from by plinux at Taobao.

The idea is that we mark all memory that are thread specific with MY_THREAD_SPECIFIC.
Memory counting is done per thread in the my_malloc_size_cb_func callback function from my_malloc().
There are plenty of new asserts to ensure that for a debug server the counting is correct.

Information_schema.processlist gets two new columns: MEMORY_USED and EXAMINED_ROWS.
- The later is there mainly to show how query is progressing.

The following changes in interfaces was needed to get this to work:
- init_alloc_root() amd init_sql_alloc() has extra option so that one can mark memory with MY_THREAD_SPECIFIC
- One now have to use alloc_root_set_min_malloc() to set min memory to be allocated by alloc_root()
- my_init_dynamic_array()  has extra option so that one can mark memory with MY_THREAD_SPECIFIC
- my_net_init() has extra option so that one can mark memory with MY_THREAD_SPECIFIC
- Added flag for hash_init() so that one can mark hash table to be thread specific.
- Added flags to init_tree() so that one can mark tree to be thread specific.
- Removed with_delete option to init_tree(). Now one should instead use MY_TREE_WITH_DELETE_FLAG.
- Added flag to Warning_info::Warning_info() if the structure should be fully initialized.
- String elements can now be marked as thread specific.
- Internal HEAP tables are now marking it's memory as MY_THREAD_SPECIFIC.
- Changed type of myf from int to ulong, as this is always a set of bit flags.

Other things:
- Removed calls to net_end() and thd->cleanup() as these are now done in ~THD()
- We now also show EXAMINED_ROWS in SHOW PROCESSLIST
- Added new variable 'memory_used'
- Fixed bug where kill_threads_for_user() was using the wrong mem_root to allocate memory.
- Removed calls to the obsoleted function init_dynamic_array()
- Use set_current_thd() instead of my_pthread_setspecific_ptr(THR_THD,...)


client/completion_hash.cc:
  Updated call to init_alloc_root()
client/mysql.cc:
  Updated call to init_alloc_root()
client/mysqlbinlog.cc:
  init_dynamic_array() -> my_init_dynamic_array()
  Updated call to init_alloc_root()
client/mysqlcheck.c:
  Updated call to my_init_dynamic_array()
client/mysqldump.c:
  Updated call to init_alloc_root()
client/mysqltest.cc:
  Updated call to init_alloc_root()
  Updated call to my_init_dynamic_array()
  Fixed compiler warnings
extra/comp_err.c:
  Updated call to my_init_dynamic_array()
extra/resolve_stack_dump.c:
  Updated call to my_init_dynamic_array()
include/hash.h:
  Added HASH_THREAD_SPECIFIC
include/heap.h:
  Added flag is internal temporary table.
include/my_dir.h:
  Safety fix: Ensure that MY_DONT_SORT and MY_WANT_STAT don't interfer with other mysys flags
include/my_global.h:
  Changed type of myf from int to ulong, as this is always a set of bit flags.
include/my_sys.h:
  Added MY_THREAD_SPECIFIC and MY_THREAD_MOVE
  Added malloc_flags to DYNAMIC_ARRAY
  Added extra mysys flag argument to my_init_dynamic_array()
  Removed deprecated functions init_dynamic_array() and my_init_dynamic_array.._ci
  Updated paramaters for init_alloc_root()
include/my_tree.h:
  Added my_flags to allow one to use MY_THREAD_SPECIFIC with hash tables.
  Removed with_delete. One should now instead use MY_TREE_WITH_DELETE_FLAG
  Updated parameters to init_tree()
include/myisamchk.h:
  Added malloc_flags to allow one to use MY_THREAD_SPECIFIC for checks.
include/mysql.h:
  Added MYSQL_THREAD_SPECIFIC_MALLOC
  Used 'unused1' to mark memory as thread specific.
include/mysql.h.pp:
  Updated file
include/mysql_com.h:
  Used 'unused1' to mark memory as thread specific.
  Updated parameters for my_net_init()
libmysql/libmysql.c:
  Updated call to init_alloc_root() to mark memory thread specific.
libmysqld/emb_qcache.cc:
  Updated call to init_alloc_root()
libmysqld/lib_sql.cc:
  Updated call to init_alloc_root()
mysql-test/r/create.result:
  Updated results
mysql-test/r/user_var.result:
  Updated results
mysql-test/suite/funcs_1/datadict/processlist_priv.inc:
  Update to handle new format of SHOW PROCESSLIST
mysql-test/suite/funcs_1/datadict/processlist_val.inc:
  Update to handle new format of SHOW PROCESSLIST
mysql-test/suite/funcs_1/r/is_columns_is.result:
  Update to handle new format of SHOW PROCESSLIST
mysql-test/suite/funcs_1/r/processlist_priv_no_prot.result:
  Updated results
mysql-test/suite/funcs_1/r/processlist_val_no_prot.result:
  Updated results
mysql-test/t/show_explain.test:
  Fixed usage of debug variable so that one can run test with --debug
mysql-test/t/user_var.test:
  Added test of memory_usage variable.
mysys/array.c:
  Added extra my_flags option to init_dynamic_array() and init_dynamic_array2() so that one can mark memory with MY_THREAD_SPECIFIC
  All allocated memory is marked with the given my_flags.
  Removed obsolete function init_dynamic_array()
mysys/default.c:
  Updated call to init_alloc_root()
  Updated call to my_init_dynamic_array()
mysys/hash.c:
  Updated call to my_init_dynamic_array_ci().
  Allocated memory is marked with MY_THREAD_SPECIFIC if HASH_THREAD_SPECIFIC is used.
mysys/ma_dyncol.c:
  init_dynamic_array() -> my_init_dynamic_array()
  Added #if to get rid of compiler warnings
mysys/mf_tempdir.c:
  Updated call to my_init_dynamic_array()
mysys/my_alloc.c:
  Added extra parameter to init_alloc_root() so that one can mark memory with MY_THREAD_SPECIFIC
  Extend MEM_ROOT with a flag if memory is thread specific.
  This is stored in block_size, to keep the size of the MEM_ROOT object identical as before.
  Allocated memory is marked with MY_THREAD_SPECIFIC if used with init_alloc_root()
mysys/my_chmod.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_chsize.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_copy.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_create.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_delete.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_error.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_fopen.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_fstream.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_getwd.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_lib.c:
  Updated call to init_alloc_root()
  Updated call to my_init_dynamic_array()
  Updated DBUG_PRINT because of change of myf type
mysys/my_lock.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_malloc.c:
  Store at start of each allocated memory block the size of the block and if the block is thread specific.
  Call malloc_size_cb_func, if set, with the memory allocated/freed.
  Updated DBUG_PRINT because of change of myf type
mysys/my_open.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_pread.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_read.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_redel.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_rename.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_seek.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_sync.c:
  Updated DBUG_PRINT because of change of myf type
mysys/my_thr_init.c:
  Ensure that one can call my_thread_dbug_id() even if thread is not properly initialized.
mysys/my_write.c:
  Updated DBUG_PRINT because of change of myf type
mysys/mysys_priv.h:
  Updated parameters to sf_malloc and sf_realloc()
mysys/safemalloc.c:
  Added checking that for memory marked with MY_THREAD_SPECIFIC that it's the same thread that is allocation and freeing the memory.
  Added sf_malloc_dbug_id() to allow MariaDB to specify which THD is handling the memory.
  Added my_flags arguments to sf_malloc() and sf_realloc() to be able to mark memory with MY_THREAD_SPECIFIC.
  Added sf_report_leaked_memory() to get list of memory not freed by a thread.
mysys/tree.c:
  Added flags to init_tree() so that one can mark tree to be thread specific.
  Removed with_delete option to init_tree(). Now one should instead use MY_TREE_WITH_DELETE_FLAG.
  Updated call to init_alloc_root()
  All allocated memory is marked with the given malloc flags
mysys/waiting_threads.c:
  Updated call to my_init_dynamic_array()
sql-common/client.c:
  Updated call to init_alloc_root() and my_net_init() to mark memory thread specific.
  Updated call to my_init_dynamic_array().
  Added MYSQL_THREAD_SPECIFIC_MALLOC so that client can mark memory as MY_THREAD_SPECIFIC.
sql-common/client_plugin.c:
  Updated call to init_alloc_root()
sql/debug_sync.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/event_scheduler.cc:
  Removed calls to net_end() as this is now done in ~THD()
  Call set_current_thd() to ensure that memory is assigned to right thread.
sql/events.cc:
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/filesort.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/filesort_utils.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/ha_ndbcluster.cc:
  Updated call to init_alloc_root()
  Updated call to my_net_init()
  Removed calls to net_end() and thd->cleanup() as these are now done in ~THD()
sql/ha_ndbcluster_binlog.cc:
  Updated call to my_net_init()
  Updated call to init_sql_alloc()
  Removed calls to net_end() and thd->cleanup() as these are now done in ~THD()
sql/ha_partition.cc:
  Updated call to init_alloc_root()
sql/handler.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
  Added missing call to my_dir_end()
sql/item_func.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/item_subselect.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/item_sum.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/log.cc:
  More DBUG
  Updated call to init_alloc_root()
sql/mdl.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/mysqld.cc:
  Added total_memory_used
  Updated call to init_alloc_root()
  Move mysql_cond_broadcast() before my_thread_end()
  Added mariadb_dbug_id() to count memory per THD instead of per thread.
  Added my_malloc_size_cb_func() callback function for my_malloc() to count memory.
  Move initialization of mysqld_server_started and mysqld_server_initialized earlier.
  Updated call to my_init_dynamic_array().
  Updated call to my_net_init().
  Call my_pthread_setspecific_ptr(THR_THD,...) to ensure that memory is assigned to right thread.
  Added status variable 'memory_used'.
  Updated call to init_alloc_root()
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/mysqld.h:
  Added set_current_thd()
sql/net_serv.cc:
  Added new parameter to my_net_init() so that one can mark memory with MY_THREAD_SPECIFIC.
  Store in net->thread_specific_malloc if memory is thread specific.
  Mark memory to be thread specific if requested.
sql/opt_range.cc:
  Updated call to my_init_dynamic_array()
  Updated call to init_sql_alloc()
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/opt_subselect.cc:
  Updated call to init_sql_alloc() to mark memory thread specific.
sql/protocol.cc:
  Fixed compiler warning
sql/records.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/rpl_filter.cc:
  Updated call to my_init_dynamic_array()
sql/rpl_handler.cc:
  Updated call to my_init_dynamic_array2()
sql/rpl_handler.h:
  Updated call to init_sql_alloc()
sql/rpl_mi.cc:
  Updated call to my_init_dynamic_array()
sql/rpl_tblmap.cc:
  Updated call to init_alloc_root()
sql/rpl_utility.cc:
  Updated call to my_init_dynamic_array()
sql/slave.cc:
  Initialize things properly before calling functions that allocate memory.
  Removed calls to net_end() as this is now done in ~THD()
sql/sp_head.cc:
  Updated call to init_sql_alloc()
  Updated call to my_init_dynamic_array()
  Added parameter to warning_info() that it should be fully initialized.
sql/sp_pcontext.cc:
  Updated call to my_init_dynamic_array()
sql/sql_acl.cc:
  Updated call to init_sql_alloc()
  Updated call to my_init_dynamic_array()
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/sql_admin.cc:
  Added parameter to warning_info() that it should be fully initialized.
sql/sql_analyse.h:
  Updated call to init_tree() to mark memory thread specific.
sql/sql_array.h:
  Updated call to my_init_dynamic_array() to mark memory thread specific.
sql/sql_audit.cc:
  Updated call to my_init_dynamic_array()
sql/sql_base.cc:
  Updated call to init_sql_alloc()
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/sql_cache.cc:
  Updated comment
sql/sql_class.cc:
  Added parameter to warning_info() that not initialize it until THD is fully created.
  Updated call to init_sql_alloc()
  Mark THD::user_vars has to be thread specific.
  Updated call to my_init_dynamic_array()
  Ensure that memory allocated by THD is assigned to the THD.
  More DBUG
  Always acll net_end() in ~THD()
  Assert that all memory signed to this THD is really deleted at ~THD.
  Fixed set_status_var_init() to not reset memory_used.
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/sql_class.h:
  Added MY_THREAD_SPECIFIC to allocated memory.
  Added malloc_size to THD to record allocated memory per THD.
sql/sql_delete.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/sql_error.cc:
  Added 'initialize' parameter to Warning_info() to say if should allocate memory for it's structures.
  This is used by THD::THD() to not allocate memory until THD is ready.
  Added Warning_info::free_memory()
sql/sql_error.h:
  Updated Warning_info() class.
sql/sql_handler.cc:
  Updated call to init_alloc_root() to mark memory thread specific.
sql/sql_insert.cc:
  More DBUG
sql/sql_join_cache.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/sql_lex.cc:
  Updated call to my_init_dynamic_array()
sql/sql_lex.h:
  Updated call to my_init_dynamic_array()
sql/sql_load.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/sql_parse.cc:
  Removed calls to net_end() and thd->cleanup() as these are now done in ~THD()
  Ensure that examined_row_count() is reset before query.
  Fixed bug where kill_threads_for_user() was using the wrong mem_root to allocate memory.
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
  Don't restore thd->status_var.memory_used when restoring thd->status_var
sql/sql_plugin.cc:
  Updated call to init_alloc_root()
  Updated call to my_init_dynamic_array()
  Don't allocate THD on the stack, as this causes problems with valgrind when doing thd memory counting.
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/sql_prepare.cc:
  Added parameter to warning_info() that it should be fully initialized.
  Updated call to init_sql_alloc() to mark memory thread specific.
sql/sql_reload.cc:
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/sql_select.cc:
  Updated call to my_init_dynamic_array() and init_sql_alloc() to mark memory thread specific.
  Added MY_THREAD_SPECIFIC to allocated memory.
  More DBUG
sql/sql_servers.cc:
  Updated call to init_sql_alloc() to mark memory some memory thread specific.
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/sql_show.cc:
  Updated call to my_init_dynamic_array()
  Mark my_dir() memory thread specific.
  Use my_pthread_setspecific_ptr(THR_THD,...) to mark that allocated memory should be allocated to calling thread.
  More DBUG.
  Added malloc_size and examined_row_count to SHOW PROCESSLIST.
  Added MY_THREAD_SPECIFIC to allocated memory.
  Updated call to init_sql_alloc()
  Added parameter to warning_info() that it should be fully initialized.
sql/sql_statistics.cc:
  Fixed compiler warning
sql/sql_string.cc:
  String elements can now be marked as thread specific.
sql/sql_string.h:
  String elements can now be marked as thread specific.
sql/sql_table.cc:
  Updated call to init_sql_alloc() and my_malloc() to mark memory thread specific
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
  Fixed compiler warning
sql/sql_test.cc:
  Updated call to my_init_dynamic_array() to mark memory thread specific.
sql/sql_trigger.cc:
  Updated call to init_sql_alloc()
sql/sql_udf.cc:
  Updated call to init_sql_alloc()
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/sql_update.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
sql/table.cc:
  Updated call to init_sql_alloc().
  Mark memory used by temporary tables, that are not for slave threads, as MY_THREAD_SPECIFIC
  Updated call to init_sql_alloc()
sql/thr_malloc.cc:
  Added my_flags argument to init_sql_alloc() to be able to mark memory as MY_THREAD_SPECIFIC.
sql/thr_malloc.h:
  Updated prototype for init_sql_alloc()
sql/tztime.cc:
  Updated call to init_sql_alloc()
  Updated call to init_alloc_root() to mark memory thread specific.
  my_pthread_setspecific_ptr(THR_THD,...) -> set_current_thd()
sql/uniques.cc:
  Updated calls to init_tree(), my_init_dynamic_array() and my_malloc() to mark memory thread specific.
sql/unireg.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
storage/csv/ha_tina.cc:
  Updated call to init_alloc_root()
storage/federated/ha_federated.cc:
  Updated call to init_alloc_root()
  Updated call to my_init_dynamic_array()
  Ensure that memory allocated by fedarated is registered for the system, not for the thread.
storage/federatedx/federatedx_io_mysql.cc:
  Updated call to my_init_dynamic_array()
storage/federatedx/ha_federatedx.cc:
  Updated call to init_alloc_root()
  Updated call to my_init_dynamic_array()
storage/heap/ha_heap.cc:
  Added MY_THREAD_SPECIFIC to allocated memory.
storage/heap/heapdef.h:
  Added parameter to hp_get_new_block() to be able to do thread specific memory tagging.
storage/heap/hp_block.c:
  Added parameter to hp_get_new_block() to be able to do thread specific memory tagging.
storage/heap/hp_create.c:
  - Internal HEAP tables are now marking it's memory as MY_THREAD_SPECIFIC.
  - Use MY_TREE_WITH_DELETE instead of removed option 'with_delete'.
storage/heap/hp_open.c:
  Internal HEAP tables are now marking it's memory as MY_THREAD_SPECIFIC.
storage/heap/hp_write.c:
  Added new parameter to hp_get_new_block()
storage/maria/ma_bitmap.c:
  Updated call to my_init_dynamic_array()
storage/maria/ma_blockrec.c:
  Updated call to my_init_dynamic_array()
storage/maria/ma_check.c:
  Updated call to init_alloc_root()
storage/maria/ma_ft_boolean_search.c:
  Updated calls to init_tree() and init_alloc_root()
storage/maria/ma_ft_nlq_search.c:
  Updated call to init_tree()
storage/maria/ma_ft_parser.c:
  Updated call to init_tree()
  Updated call to init_alloc_root()
storage/maria/ma_loghandler.c:
  Updated call to my_init_dynamic_array()
storage/maria/ma_open.c:
  Updated call to my_init_dynamic_array()
storage/maria/ma_sort.c:
  Updated call to my_init_dynamic_array()
storage/maria/ma_write.c:
  Updated calls to my_init_dynamic_array() and init_tree()
storage/maria/maria_pack.c:
  Updated call to init_tree()
storage/maria/unittest/sequence_storage.c:
  Updated call to my_init_dynamic_array()
storage/myisam/ft_boolean_search.c:
  Updated call to init_tree()
  Updated call to init_alloc_root()
storage/myisam/ft_nlq_search.c:
  Updated call to init_tree()
storage/myisam/ft_parser.c:
  Updated call to init_tree()
  Updated call to init_alloc_root()
storage/myisam/ft_stopwords.c:
  Updated call to init_tree()
storage/myisam/mi_check.c:
  Updated call to init_alloc_root()
storage/myisam/mi_write.c:
  Updated call to my_init_dynamic_array()
  Updated call to init_tree()
storage/myisam/myisamlog.c:
  Updated call to init_tree()
storage/myisam/myisampack.c:
  Updated call to init_tree()
storage/myisam/sort.c:
  Updated call to my_init_dynamic_array()
storage/myisammrg/ha_myisammrg.cc:
  Updated call to init_sql_alloc()
storage/perfschema/pfs_check.cc:
  Rest current_thd
storage/perfschema/pfs_instr.cc:
  Removed DBUG_ENTER/DBUG_VOID_RETURN as at this point my_thread_var is not allocated anymore, which can cause problems.
support-files/compiler_warnings.supp:
  Disable compiler warning from offsetof macro.

1 files changed, 20 insertions, 7 deletions

diff --git a/sql/sql_string.h b/sql/sql_string.h
index 2966fc2a920..58cda343dac 100644
--- a/sql/sql_string.h
+++ b/sql/sql_string.h
@@ -56,23 +56,26 @@ class String
 {
   char *Ptr;
   uint32 str_length,Alloced_length, extra_alloc;
-  bool alloced;
+  bool alloced,thread_specific;
   CHARSET_INFO *str_charset;
 public:
   String()
   { 
-    Ptr=0; str_length=Alloced_length=extra_alloc=0; alloced=0; 
+    Ptr=0; str_length=Alloced_length=extra_alloc=0;
+    alloced= thread_specific= 0; 
     str_charset= &my_charset_bin; 
   }
   String(uint32 length_arg)
   { 
-    alloced=0; Alloced_length= extra_alloc= 0; (void) real_alloc(length_arg); 
+    alloced= thread_specific= 0;
+    Alloced_length= extra_alloc= 0; (void) real_alloc(length_arg); 
     str_charset= &my_charset_bin;
   }
   String(const char *str, CHARSET_INFO *cs)
   { 
     Ptr=(char*) str; str_length= (uint32) strlen(str);
-    Alloced_length= extra_alloc= 0; alloced=0;
+    Alloced_length= extra_alloc= 0;
+    alloced= thread_specific= 0;
     str_charset=cs;
   }
   /*
@@ -82,18 +85,21 @@ public:
   */
   String(const char *str,uint32 len, CHARSET_INFO *cs)
   { 
-    Ptr=(char*) str; str_length=len; Alloced_length= extra_alloc=0; alloced=0;
+    Ptr=(char*) str; str_length=len; Alloced_length= extra_alloc=0;
+    alloced= thread_specific= 0;
     str_charset=cs;
   }
   String(char *str,uint32 len, CHARSET_INFO *cs)
   { 
-    Ptr=(char*) str; Alloced_length=str_length=len; extra_alloc= 0; alloced=0;
+    Ptr=(char*) str; Alloced_length=str_length=len; extra_alloc= 0;
+    alloced= thread_specific= 0;
     str_charset=cs;
   }
   String(const String &str)
   { 
     Ptr=str.Ptr ; str_length=str.str_length ;
-    Alloced_length=str.Alloced_length; extra_alloc= 0; alloced=0; 
+    Alloced_length=str.Alloced_length; extra_alloc= 0;
+    alloced= thread_specific= 0;
     str_charset=str.str_charset;
   }
   static void *operator new(size_t size, MEM_ROOT *mem_root) throw ()
@@ -108,6 +114,12 @@ public:
   { /* never called */ }
   ~String() { free(); }
 
+  /* Mark variable thread specific it it's not allocated already */
+  inline void set_thread_specific()
+  {
+    if (!alloced)
+      thread_specific= 1;
+  }
   inline void set_charset(CHARSET_INFO *charset_arg)
   { str_charset= charset_arg; }
   inline CHARSET_INFO *charset() const { return str_charset; }
@@ -332,6 +344,7 @@ public:
     Ptr=s.Ptr ; str_length=s.str_length ; Alloced_length=s.Alloced_length;
     extra_alloc= s.extra_alloc;
     alloced= s.alloced;
+    thread_specific= s.thread_specific;
     s.alloced= 0;
   }
   bool append(const String &s);