Bug#28234 - global/session scope - documentation vs implementation

Several system variables did not behave like system variables should do.
When trying to SET them or use them in SELECT, they were reported as
"unknown system variable". But they appeared in SHOW VARIABLES.

This has been fixed by removing the "fixed_vars" array of variables
and integrating the variables into the normal system variables chain.
All of these variables do now behave as read-only global-only
variables. Trying to SET them tells they are read-only, trying to
SELECT the session value tells they are global only. Selecting the
global value works. It delivers the same value as SHOW VARIABLES.

mysql-test/r/variables-notembedded.result

@@ -15,3 +15,95 @@ slave_skip_errors	3,100,137,643,1752
 ---- Clean Up ----
 set global slave_net_timeout=default;
 set global sql_slave_skip_counter= 0;
+
+#
+SHOW VARIABLES like 'log_slave_updates';
+Variable_name	Value
+log_slave_updates	OFF
+SELECT @@session.log_slave_updates;
+ERROR HY000: Variable 'log_slave_updates' is a GLOBAL variable
+SELECT @@global.log_slave_updates;
+@@global.log_slave_updates
+0
+SET @@session.log_slave_updates= true;
+ERROR HY000: Variable 'log_slave_updates' is a read only variable
+SET @@global.log_slave_updates= true;
+ERROR HY000: Variable 'log_slave_updates' is a read only variable
+#
+SHOW VARIABLES like 'relay_log';
+Variable_name	Value
+relay_log	
+SELECT @@session.relay_log;
+ERROR HY000: Variable 'relay_log' is a GLOBAL variable
+SELECT @@global.relay_log;
+@@global.relay_log
+NULL
+SET @@session.relay_log= 'x';
+ERROR HY000: Variable 'relay_log' is a read only variable
+SET @@global.relay_log= 'x';
+ERROR HY000: Variable 'relay_log' is a read only variable
+#
+SHOW VARIABLES like 'relay_log_index';
+Variable_name	Value
+relay_log_index	
+SELECT @@session.relay_log_index;
+ERROR HY000: Variable 'relay_log_index' is a GLOBAL variable
+SELECT @@global.relay_log_index;
+@@global.relay_log_index
+NULL
+SET @@session.relay_log_index= 'x';
+ERROR HY000: Variable 'relay_log_index' is a read only variable
+SET @@global.relay_log_index= 'x';
+ERROR HY000: Variable 'relay_log_index' is a read only variable
+#
+SHOW VARIABLES like 'relay_log_info_file';
+Variable_name	Value
+relay_log_info_file	relay-log.info
+SELECT @@session.relay_log_info_file;
+ERROR HY000: Variable 'relay_log_info_file' is a GLOBAL variable
+SELECT @@global.relay_log_info_file;
+@@global.relay_log_info_file
+relay-log.info
+SET @@session.relay_log_info_file= 'x';
+ERROR HY000: Variable 'relay_log_info_file' is a read only variable
+SET @@global.relay_log_info_file= 'x';
+ERROR HY000: Variable 'relay_log_info_file' is a read only variable
+#
+SHOW VARIABLES like 'relay_log_space_limit';
+Variable_name	Value
+relay_log_space_limit	0
+SELECT @@session.relay_log_space_limit;
+ERROR HY000: Variable 'relay_log_space_limit' is a GLOBAL variable
+SELECT @@global.relay_log_space_limit;
+@@global.relay_log_space_limit
+0
+SET @@session.relay_log_space_limit= 7;
+ERROR HY000: Variable 'relay_log_space_limit' is a read only variable
+SET @@global.relay_log_space_limit= 7;
+ERROR HY000: Variable 'relay_log_space_limit' is a read only variable
+#
+SHOW VARIABLES like 'slave_load_tmpdir';
+Variable_name	Value
+slave_load_tmpdir	#
+SELECT @@session.slave_load_tmpdir;
+ERROR HY000: Variable 'slave_load_tmpdir' is a GLOBAL variable
+SELECT @@global.slave_load_tmpdir;
+@@global.slave_load_tmpdir
+#
+SET @@session.slave_load_tmpdir= 'x';
+ERROR HY000: Variable 'slave_load_tmpdir' is a read only variable
+SET @@global.slave_load_tmpdir= 'x';
+ERROR HY000: Variable 'slave_load_tmpdir' is a read only variable
+#
+SHOW VARIABLES like 'slave_skip_errors';
+Variable_name	Value
+slave_skip_errors	3,100,137,643,1752
+SELECT @@session.slave_skip_errors;
+ERROR HY000: Variable 'slave_skip_errors' is a GLOBAL variable
+SELECT @@global.slave_skip_errors;
+@@global.slave_skip_errors
+3,100,137,643,1752
+SET @@session.slave_skip_errors= 7;
+ERROR HY000: Variable 'slave_skip_errors' is a read only variable
+SET @@global.slave_skip_errors= 7;
+ERROR HY000: Variable 'slave_skip_errors' is a read only variable

mysql-test/t/variables-notembedded.test

@@ -28,3 +28,83 @@ set global slave_net_timeout=default;
 # sql_slave_skip_counter is write-only, so we can't save previous
 # value and restore it here.  That's ok, because it's normally 0.
 set global sql_slave_skip_counter= 0;
+
+#
+# Bug#28234 - global/session scope - documentation vs implementation
+#
+--echo
+#
+# Additional variables fixed from sql_repl.cc.
+#
+--echo #
+SHOW VARIABLES like 'log_slave_updates';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.log_slave_updates;
+SELECT @@global.log_slave_updates;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.log_slave_updates= true;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.log_slave_updates= true;
+#
+--echo #
+SHOW VARIABLES like 'relay_log';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.relay_log;
+SELECT @@global.relay_log;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.relay_log= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.relay_log= 'x';
+#
+--echo #
+SHOW VARIABLES like 'relay_log_index';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.relay_log_index;
+SELECT @@global.relay_log_index;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.relay_log_index= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.relay_log_index= 'x';
+#
+--echo #
+SHOW VARIABLES like 'relay_log_info_file';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.relay_log_info_file;
+SELECT @@global.relay_log_info_file;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.relay_log_info_file= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.relay_log_info_file= 'x';
+#
+--echo #
+SHOW VARIABLES like 'relay_log_space_limit';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.relay_log_space_limit;
+SELECT @@global.relay_log_space_limit;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.relay_log_space_limit= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.relay_log_space_limit= 7;
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'slave_load_tmpdir';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.slave_load_tmpdir;
+--replace_column 1 #
+SELECT @@global.slave_load_tmpdir;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.slave_load_tmpdir= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.slave_load_tmpdir= 'x';
+#
+--echo #
+SHOW VARIABLES like 'slave_skip_errors';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.slave_skip_errors;
+SELECT @@global.slave_skip_errors;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.slave_skip_errors= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.slave_skip_errors= 7;
+#

mysql-test/t/variables.test

@@ -793,3 +793,299 @@ SET GLOBAL log_output = 0;
 --echo
 --echo # -- End of Bug#34820.
 
+#
+# Bug#28234 - global/session scope - documentation vs implementation
+#
+--echo
+--echo #
+SHOW VARIABLES like 'ft_max_word_len';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.ft_max_word_len;
+SELECT @@global.ft_max_word_len;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.ft_max_word_len= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.ft_max_word_len= 7;
+#
+--echo #
+SHOW VARIABLES like 'ft_min_word_len';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.ft_min_word_len;
+SELECT @@global.ft_min_word_len;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.ft_min_word_len= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.ft_min_word_len= 7;
+#
+--echo #
+SHOW VARIABLES like 'ft_query_expansion_limit';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.ft_query_expansion_limit;
+SELECT @@global.ft_query_expansion_limit;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.ft_query_expansion_limit= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.ft_query_expansion_limit= 7;
+#
+--echo #
+SHOW VARIABLES like 'ft_stopword_file';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.ft_stopword_file;
+SELECT @@global.ft_stopword_file;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.ft_stopword_file= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.ft_stopword_file= 'x';
+#
+# Additional variables fixed.
+#
+--echo #
+SHOW VARIABLES like 'back_log';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.back_log;
+SELECT @@global.back_log;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.back_log= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.back_log= 7;
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'large_files_support';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.large_files_support;
+--replace_column 1 #
+SELECT @@global.large_files_support;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.large_files_support= true;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.large_files_support= true;
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'character_sets_dir';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.character_sets_dir;
+--replace_column 1 #
+SELECT @@global.character_sets_dir;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.character_sets_dir= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.character_sets_dir= 'x';
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'init_file';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.init_file;
+--replace_column 1 #
+SELECT @@global.init_file;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.init_file= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.init_file= 'x';
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'language';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.language;
+--replace_column 1 #
+SELECT @@global.language;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.language= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.language= 'x';
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'large_page_size';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.large_page_size;
+--replace_column 1 #
+SELECT @@global.large_page_size;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.large_page_size= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.large_page_size= 7;
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'large_pages';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.large_pages;
+--replace_column 1 #
+SELECT @@global.large_pages;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.large_pages= true;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.large_pages= true;
+#
+--echo #
+SHOW VARIABLES like 'log_bin';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.log_bin;
+SELECT @@global.log_bin;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.log_bin= true;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.log_bin= true;
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'log_error';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.log_error;
+--replace_column 1 #
+SELECT @@global.log_error;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.log_error= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.log_error= 'x';
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'lower_case_file_system';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.lower_case_file_system;
+--replace_column 1 #
+SELECT @@global.lower_case_file_system;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.lower_case_file_system= true;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.lower_case_file_system= true;
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'lower_case_table_names';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.lower_case_table_names;
+--replace_column 1 #
+SELECT @@global.lower_case_table_names;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.lower_case_table_names= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.lower_case_table_names= 7;
+#
+--echo #
+SHOW VARIABLES like 'myisam_recover_options';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.myisam_recover_options;
+SELECT @@global.myisam_recover_options;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.myisam_recover_options= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.myisam_recover_options= 'x';
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'open_files_limit';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.open_files_limit;
+--replace_column 1 #
+SELECT @@global.open_files_limit;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.open_files_limit= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.open_files_limit= 7;
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'pid_file';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.pid_file;
+--replace_column 1 #
+SELECT @@global.pid_file;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.pid_file= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.pid_file= 'x';
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'plugin_dir';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.plugin_dir;
+--replace_column 1 #
+SELECT @@global.plugin_dir;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.plugin_dir= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.plugin_dir= 'x';
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'port';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.port;
+--replace_column 1 #
+SELECT @@global.port;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.port= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.port= 7;
+#
+--echo #
+SHOW VARIABLES like 'protocol_version';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.protocol_version;
+SELECT @@global.protocol_version;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.protocol_version= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.protocol_version= 7;
+#
+--echo #
+SHOW VARIABLES like 'skip_external_locking';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.skip_external_locking;
+SELECT @@global.skip_external_locking;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.skip_external_locking= true;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.skip_external_locking= true;
+#
+--echo #
+SHOW VARIABLES like 'skip_networking';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.skip_networking;
+SELECT @@global.skip_networking;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.skip_networking= true;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.skip_networking= true;
+#
+--echo #
+SHOW VARIABLES like 'skip_show_database';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.skip_show_database;
+SELECT @@global.skip_show_database;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.skip_show_database= true;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.skip_show_database= true;
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'socket';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.socket;
+--replace_column 1 #
+SELECT @@global.socket;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.socket= 'x';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.socket= 'x';
+#
+--echo #
+--replace_column 2 #
+SHOW VARIABLES like 'thread_stack';
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SELECT @@session.thread_stack;
+--replace_column 1 #
+SELECT @@global.thread_stack;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@session.thread_stack= 7;
+--error ER_INCORRECT_GLOBAL_LOCAL_VAR
+SET @@global.thread_stack= 7;
+#

sql/item_func.cc

@@ -4855,6 +4855,7 @@ void Item_func_get_system_var::fix_length_and_dec()
       max_length= MAX_BLOB_WIDTH;
       decimals=NOT_FIXED_DEC;
       break;
+    case SHOW_BOOL:
     case SHOW_MY_BOOL:
       unsigned_flag= FALSE;
       max_length= 1;
@@ -4882,6 +4883,7 @@ enum Item_result Item_func_get_system_var::result_type() const
 {
   switch (var->show_type())
   {
+    case SHOW_BOOL:
     case SHOW_MY_BOOL:
     case SHOW_INT:
     case SHOW_LONG:
@@ -4904,6 +4906,7 @@ enum_field_types Item_func_get_system_var::field_type() const
 {
   switch (var->show_type())
   {
+    case SHOW_BOOL:
     case SHOW_MY_BOOL:
     case SHOW_INT:
     case SHOW_LONG:
@@ -4922,6 +4925,10 @@ enum_field_types Item_func_get_system_var::field_type() const
 }
 
 
+/*
+  Uses var, var_type, component, cache_present, used_query_id, thd,
+  cached_llval, null_value, cached_null_value
+*/
 #define get_sys_var_safe(type) \
 do { \
   type value; \
@@ -4975,6 +4982,7 @@ longlong Item_func_get_system_var::val_int()
     case SHOW_LONG:     get_sys_var_safe (ulong);
     case SHOW_LONGLONG: get_sys_var_safe (longlong);
     case SHOW_HA_ROWS:  get_sys_var_safe (ha_rows);
+    case SHOW_BOOL:     get_sys_var_safe (bool);
     case SHOW_MY_BOOL:  get_sys_var_safe (my_bool);
     case SHOW_DOUBLE:
       {
@@ -5072,6 +5080,7 @@ String* Item_func_get_system_var::val_str(String* str)
     case SHOW_LONG:
     case SHOW_LONGLONG:
     case SHOW_HA_ROWS:
+    case SHOW_BOOL:
     case SHOW_MY_BOOL:
       str->set (val_int(), collation.collation);
       break;
@@ -5164,6 +5173,7 @@ double Item_func_get_system_var::val_real()
     case SHOW_LONG:
     case SHOW_LONGLONG:
     case SHOW_HA_ROWS:
+    case SHOW_BOOL:
     case SHOW_MY_BOOL:
         cached_dval= (double) val_int();
         cache_present|= GET_SYS_VAR_CACHE_DOUBLE;

sql/set_var.h

@@ -929,6 +929,34 @@ class sys_var_readonly: public sys_var
 };
 
 
+/**
+  Global-only, read-only variable. E.g. command line option.
+*/
+
+class sys_var_const: public sys_var
+{
+public:
+  enum_var_type var_type;
+  SHOW_TYPE show_type_value;
+  uchar *ptr;
+  sys_var_const(sys_var_chain *chain, const char *name_arg, enum_var_type type,
+                SHOW_TYPE show_type_arg, uchar *ptr_arg)
+    :sys_var(name_arg), var_type(type),
+    show_type_value(show_type_arg), ptr(ptr_arg)
+  { chain_sys_var(chain); }
+  bool update(THD *thd, set_var *var) { return 1; }
+  bool check_default(enum_var_type type) { return 1; }
+  bool check_type(enum_var_type type) { return type != var_type; }
+  bool check_update_type(Item_result type) { return 1; }
+  uchar *value_ptr(THD *thd, enum_var_type type, LEX_STRING *base)
+  {
+    return ptr;
+  }
+  SHOW_TYPE show_type() { return show_type_value; }
+  bool is_readonly() const { return 1; }
+};
+
+
 class sys_var_have_option: public sys_var
 {
 protected:
@@ -1317,7 +1345,6 @@ struct sys_var_with_base
 
 int set_var_init();
 void set_var_free();
-int mysql_append_static_vars(const SHOW_VAR *show_vars, uint count);
 SHOW_VAR* enumerate_sys_vars(THD *thd, bool sorted);
 int mysql_add_sys_var_chain(sys_var *chain, struct my_option *long_options);
 int mysql_del_sys_var_chain(sys_var *chain);

sql/slave.cc

@@ -49,6 +49,7 @@
 #define MAX_SLAVE_RETRY_PAUSE 5
 bool use_slave_mask = 0;
 MY_BITMAP slave_error_mask;
+char slave_skip_error_names[SHOW_VAR_FUNC_BUFF_SIZE];
 
 typedef bool (*CHECK_KILLED_FUNC)(THD*,void*);
 
@@ -275,6 +276,64 @@ int init_slave()
 }
 
 
+/**
+  Convert slave skip errors bitmap into a printable string.
+*/
+
+static void print_slave_skip_errors(void)
+{
+  /*
+    To be safe, we want 10 characters of room in the buffer for a number
+    plus terminators. Also, we need some space for constant strings.
+    10 characters must be sufficient for a number plus {',' | '...'}
+    plus a NUL terminator. That is a max 6 digit number.
+  */
+  const int MIN_ROOM= 10;
+  DBUG_ENTER("print_slave_skip_errors");
+  DBUG_ASSERT(sizeof(slave_skip_error_names) > MIN_ROOM);
+  DBUG_ASSERT(MAX_SLAVE_ERROR <= 999999); // 6 digits
+
+  if (!use_slave_mask || bitmap_is_clear_all(&slave_error_mask))
+  {
+    /* purecov: begin tested */
+    memcpy(slave_skip_error_names, STRING_WITH_LEN("OFF"));
+    /* purecov: end */
+  }
+  else if (bitmap_is_set_all(&slave_error_mask))
+  {
+    /* purecov: begin tested */
+    memcpy(slave_skip_error_names, STRING_WITH_LEN("ALL"));
+    /* purecov: end */
+  }
+  else
+  {
+    char *buff= slave_skip_error_names;
+    char *bend= buff + sizeof(slave_skip_error_names);
+    int  errnum;
+
+    for (errnum= 1; errnum < MAX_SLAVE_ERROR; errnum++)
+    {
+      if (bitmap_is_set(&slave_error_mask, errnum))
+      {
+        if (buff + MIN_ROOM >= bend)
+          break; /* purecov: tested */
+        buff= int10_to_str(errnum, buff, 10);
+        *buff++= ',';
+      }
+    }
+    if (buff != slave_skip_error_names)
+      buff--; // Remove last ','
+    if (errnum < MAX_SLAVE_ERROR)
+    {
+      /* Couldn't show all errors */
+      buff= strmov(buff, "..."); /* purecov: tested */
+    }
+    *buff=0;
+  }
+  DBUG_PRINT("init", ("error_names: '%s'", slave_skip_error_names));
+  DBUG_VOID_RETURN;
+}
+
 /*
   Init function to set up array for errors that should be skipped for slave
 
@@ -314,6 +373,8 @@ void init_slave_skip_errors(const char* arg)
     while (!my_isdigit(system_charset_info,*p) && *p)
       p++;
   }
+  /* Convert slave skip errors bitmap into a printable string. */
+  print_slave_skip_errors();
   DBUG_VOID_RETURN;
 }
 

sql/slave.h

@@ -98,6 +98,7 @@ class Master_info;
 
 extern ulong master_retry_count;
 extern MY_BITMAP slave_error_mask;
+extern char slave_skip_error_names[];
 extern bool use_slave_mask;
 extern char *slave_load_tmpdir;
 extern char *master_info_file, *relay_log_info_file;

sql/sql_repl.cc

@@ -1660,64 +1660,38 @@ class sys_var_sync_binlog_period :public sys_var_long_ptr
 
 static sys_var_chain vars = { NULL, NULL };
 
+static sys_var_const    sys_log_slave_updates(&vars, "log_slave_updates",
+                                              OPT_GLOBAL, SHOW_MY_BOOL,
+                                              (uchar*) &opt_log_slave_updates);
+static sys_var_const    sys_relay_log(&vars, "relay_log",
+                                      OPT_GLOBAL, SHOW_CHAR_PTR,
+                                      (uchar*) &opt_relay_logname);
+static sys_var_const    sys_relay_log_index(&vars, "relay_log_index",
+                                      OPT_GLOBAL, SHOW_CHAR_PTR,
+                                      (uchar*) &opt_relaylog_index_name);
+static sys_var_const    sys_relay_log_info_file(&vars, "relay_log_info_file",
+                                      OPT_GLOBAL, SHOW_CHAR_PTR,
+                                      (uchar*) &relay_log_info_file);
 static sys_var_bool_ptr	sys_relay_log_purge(&vars, "relay_log_purge",
 					    &relay_log_purge);
+static sys_var_const    sys_relay_log_space_limit(&vars,
+                                                  "relay_log_space_limit",
+                                                  OPT_GLOBAL, SHOW_LONGLONG,
+                                                  (uchar*)
+                                                  &relay_log_space_limit);
+static sys_var_const    sys_slave_load_tmpdir(&vars, "slave_load_tmpdir",
+                                              OPT_GLOBAL, SHOW_CHAR_PTR,
+                                              (uchar*) &slave_load_tmpdir);
 static sys_var_long_ptr	sys_slave_net_timeout(&vars, "slave_net_timeout",
 					      &slave_net_timeout);
+static sys_var_const    sys_slave_skip_errors(&vars, "slave_skip_errors",
+                                              OPT_GLOBAL, SHOW_CHAR,
+                                              (uchar*) slave_skip_error_names);
 static sys_var_long_ptr	sys_slave_trans_retries(&vars, "slave_transaction_retries",
 						&slave_trans_retries);
 static sys_var_sync_binlog_period sys_sync_binlog_period(&vars, "sync_binlog", &sync_binlog_period);
 static sys_var_slave_skip_counter sys_slave_skip_counter(&vars, "sql_slave_skip_counter");
 
-static int show_slave_skip_errors(THD *thd, SHOW_VAR *var, char *buff);
-
-
-static SHOW_VAR fixed_vars[]= {
-  {"log_slave_updates",       (char*) &opt_log_slave_updates,       SHOW_MY_BOOL},
-  {"relay_log" , (char*) &opt_relay_logname, SHOW_CHAR_PTR},
-  {"relay_log_index", (char*) &opt_relaylog_index_name, SHOW_CHAR_PTR},
-  {"relay_log_info_file", (char*) &relay_log_info_file, SHOW_CHAR_PTR},
-  {"relay_log_space_limit",   (char*) &relay_log_space_limit,       SHOW_LONGLONG},
-  {"slave_load_tmpdir",       (char*) &slave_load_tmpdir,           SHOW_CHAR_PTR},
-  {"slave_skip_errors",       (char*) &show_slave_skip_errors,      SHOW_FUNC},
-};
-
-static int show_slave_skip_errors(THD *thd, SHOW_VAR *var, char *buff)
-{
-  var->type=SHOW_CHAR;
-  var->value= buff;
-  if (!use_slave_mask || bitmap_is_clear_all(&slave_error_mask))
-  {
-    var->value= const_cast<char *>("OFF");
-  }
-  else if (bitmap_is_set_all(&slave_error_mask))
-  {
-    var->value= const_cast<char *>("ALL");
-  }
-  else
-  {
-    /* 10 is enough assuming errors are max 4 digits */
-    int i;
-    var->value= buff;
-    for (i= 1;
-         i < MAX_SLAVE_ERROR &&
-         (buff - var->value) < SHOW_VAR_FUNC_BUFF_SIZE;
-         i++)
-    {
-      if (bitmap_is_set(&slave_error_mask, i))
-      {
-        buff= int10_to_str(i, buff, 10);
-        *buff++= ',';
-      }
-    }
-    if (var->value != buff)
-      buff--;				// Remove last ','
-    if (i < MAX_SLAVE_ERROR)
-      buff= strmov(buff, "...");  // Couldn't show all errors
-    *buff=0;
-  }
-  return 0;
-}
 
 bool sys_var_slave_skip_counter::check(THD *thd, set_var *var)
 {
@@ -1765,8 +1739,6 @@ bool sys_var_sync_binlog_period::update(THD *thd, set_var *var)
 
 int init_replication_sys_vars()
 {
-  mysql_append_static_vars(fixed_vars, sizeof(fixed_vars) / sizeof(SHOW_VAR));
-
   if (mysql_add_sys_var_chain(vars.first, my_long_options))
   {
     /* should not happen */