Bug#16194302: SUPPORT FOR FLOATING-POINT SYSTEM VARIABLES

              USING THE PLUGIN INTERFACE.

ISSUE: No support for floating-point plugin
       system variables.

SOLUTION: Allowing plugins to define and expose floating-point
          system variables of type double. MYSQL_SYSVAR_DOUBLE
          and MYSQL_THDVAR_DOUBLE are added.

ISSUE: Fractional part of the def, min, max values of system
       variables are ignored.

SOLUTION: Adding functions that are used to store the raw
          representation of a double in the raw bits of unsigned
          longlong in a way that the binary representation
          remains the same.

include/my_getopt.h

@@ -120,6 +120,9 @@ double getopt_double_limit_value(double num, const struct my_option *optp,
                                  my_bool *fix);
 my_bool getopt_compare_strings(const char *s, const char *t, uint length);
 
+ulonglong getopt_double2ulonglong(double);
+double getopt_ulonglong2double(ulonglong);
+
 C_MODE_END
 
 #endif /* _my_getopt_h */

include/mysql/plugin.h

@@ -163,6 +163,7 @@ typedef int (*mysql_show_var_func)(MYSQL_THD, struct st_mysql_show_var*, char *)
 #define PLUGIN_VAR_STR          0x0005
 #define PLUGIN_VAR_ENUM         0x0006
 #define PLUGIN_VAR_SET          0x0007
+#define PLUGIN_VAR_DOUBLE       0x0008
 #define PLUGIN_VAR_UNSIGNED     0x0080
 #define PLUGIN_VAR_THDLOCAL     0x0100 /* Variable is per-connection */
 #define PLUGIN_VAR_READONLY     0x0200 /* Server variable is read only */
@@ -345,6 +346,11 @@ DECLARE_MYSQL_SYSVAR_TYPELIB(name, unsigned long long) = { \
   PLUGIN_VAR_SET | ((opt) & PLUGIN_VAR_MASK), \
   #name, comment, check, update, &varname, def, typelib }
 
+#define MYSQL_SYSVAR_DOUBLE(name, varname, opt, comment, check, update, def, min, max, blk) \
+DECLARE_MYSQL_SYSVAR_SIMPLE(name, double) = { \
+  PLUGIN_VAR_DOUBLE | ((opt) & PLUGIN_VAR_MASK), \
+  #name, comment, check, update, &varname, def, min, max, blk }
+
 #define MYSQL_THDVAR_BOOL(name, opt, comment, check, update, def) \
 DECLARE_MYSQL_THDVAR_BASIC(name, char) = { \
   PLUGIN_VAR_BOOL | PLUGIN_VAR_THDLOCAL | ((opt) & PLUGIN_VAR_MASK), \
@@ -395,6 +401,11 @@ DECLARE_MYSQL_THDVAR_TYPELIB(name, unsigned long long) = { \
   PLUGIN_VAR_SET | PLUGIN_VAR_THDLOCAL | ((opt) & PLUGIN_VAR_MASK), \
   #name, comment, check, update, -1, def, NULL, typelib }
 
+#define MYSQL_THDVAR_DOUBLE(name, opt, comment, check, update, def, min, max, blk) \
+DECLARE_MYSQL_THDVAR_SIMPLE(name, double) = { \
+  PLUGIN_VAR_DOUBLE | PLUGIN_VAR_THDLOCAL | ((opt) & PLUGIN_VAR_MASK), \
+  #name, comment, check, update, -1, def, min, max, blk, NULL }
+
 /* accessor macros */
 
 #define SYSVAR(name) \

mysql-test/r/plugin.result

@@ -16,9 +16,11 @@ set global example_ulong_var=500;
 set global example_enum_var= e1;
 show status like 'example%';
 Variable_name	Value
-example_func_example	enum_var is 0, ulong_var is 500, really
+example_func_example	enum_var is 0, ulong_var is 500, double_var is 8.500000, really
 show variables like 'example%';
 Variable_name	Value
+example_double_thdvar	8.500000
+example_double_var	8.500000
 example_enum_var	e1
 example_ulong_var	500
 UNINSTALL PLUGIN example;
@@ -63,3 +65,81 @@ set session sql_mode=@old_sql_mode;
 set session old=bla;
 ERROR HY000: Variable 'old' is a read only variable
 UNINSTALL PLUGIN example;
+#
+# Bug #16194302  SUPPORT FOR FLOATING-POINT SYSTEM
+#                VARIABLES USING THE PLUGIN INTERFACE.
+#
+INSTALL PLUGIN example SONAME 'ha_example.so';
+SET GLOBAL example_double_var = -0.1;
+Warnings:
+Warning	1292	Truncated incorrect example_double_var value: '-0.1'
+SELECT @@GLOBAL.example_double_var;
+@@GLOBAL.example_double_var
+0.500000
+SET GLOBAL example_double_var = 0.000001;
+Warnings:
+Warning	1292	Truncated incorrect example_double_var value: '0.000001'
+SELECT @@GLOBAL.example_double_var;
+@@GLOBAL.example_double_var
+0.500000
+SET GLOBAL example_double_var = 0.4;
+Warnings:
+Warning	1292	Truncated incorrect example_double_var value: '0.4'
+SELECT @@GLOBAL.example_double_var;
+@@GLOBAL.example_double_var
+0.500000
+SET GLOBAL example_double_var = 123.456789;
+SELECT @@GLOBAL.example_double_var;
+@@GLOBAL.example_double_var
+123.456789
+SET GLOBAL example_double_var = 500;
+SELECT @@GLOBAL.example_double_var;
+@@GLOBAL.example_double_var
+500.000000
+SET GLOBAL example_double_var = 999.999999;
+SELECT @@GLOBAL.example_double_var;
+@@GLOBAL.example_double_var
+999.999999
+SET GLOBAL example_double_var = 1000.51;
+Warnings:
+Warning	1292	Truncated incorrect example_double_var value: '1000.51'
+SELECT @@GLOBAL.example_double_var;
+@@GLOBAL.example_double_var
+1000.500000
+SET SESSION example_double_thdvar = -0.1;
+Warnings:
+Warning	1292	Truncated incorrect example_double_thdvar value: '-0.1'
+SELECT @@SESSION.example_double_thdvar;
+@@SESSION.example_double_thdvar
+0.500000
+SET SESSION example_double_thdvar = 0.000001;
+Warnings:
+Warning	1292	Truncated incorrect example_double_thdvar value: '0.000001'
+SELECT @@SESSION.example_double_thdvar;
+@@SESSION.example_double_thdvar
+0.500000
+SET SESSION example_double_thdvar = 0.4;
+Warnings:
+Warning	1292	Truncated incorrect example_double_thdvar value: '0.4'
+SELECT @@SESSION.example_double_thdvar;
+@@SESSION.example_double_thdvar
+0.500000
+SET SESSION example_double_thdvar = 123.456789;
+SELECT @@SESSION.example_double_thdvar;
+@@SESSION.example_double_thdvar
+123.456789
+SET SESSION example_double_thdvar = 500;
+SELECT @@SESSION.example_double_thdvar;
+@@SESSION.example_double_thdvar
+500.000000
+SET SESSION example_double_thdvar = 999.999999;
+SELECT @@SESSION.example_double_thdvar;
+@@SESSION.example_double_thdvar
+999.999999
+SET SESSION example_double_thdvar = 1000.51;
+Warnings:
+Warning	1292	Truncated incorrect example_double_thdvar value: '1000.51'
+SELECT @@SESSION.example_double_thdvar;
+@@SESSION.example_double_thdvar
+1000.500000
+UNINSTALL PLUGIN example;

mysql-test/t/plugin.test

@@ -85,3 +85,55 @@ set session sql_mode=@old_sql_mode;
 set session old=bla;
 
 UNINSTALL PLUGIN example;
+
+--echo #
+--echo # Bug #16194302  SUPPORT FOR FLOATING-POINT SYSTEM
+--echo #                VARIABLES USING THE PLUGIN INTERFACE.
+--echo #
+
+--replace_regex /\.dll/.so/
+eval INSTALL PLUGIN example SONAME '$EXAMPLE_PLUGIN';
+
+SET GLOBAL example_double_var = -0.1;
+SELECT @@GLOBAL.example_double_var;
+
+SET GLOBAL example_double_var = 0.000001;
+SELECT @@GLOBAL.example_double_var;
+
+SET GLOBAL example_double_var = 0.4;
+SELECT @@GLOBAL.example_double_var;
+
+SET GLOBAL example_double_var = 123.456789;
+SELECT @@GLOBAL.example_double_var;
+
+SET GLOBAL example_double_var = 500;
+SELECT @@GLOBAL.example_double_var;
+
+SET GLOBAL example_double_var = 999.999999;
+SELECT @@GLOBAL.example_double_var;
+
+SET GLOBAL example_double_var = 1000.51;
+SELECT @@GLOBAL.example_double_var;
+
+SET SESSION example_double_thdvar = -0.1;
+SELECT @@SESSION.example_double_thdvar;
+
+SET SESSION example_double_thdvar = 0.000001;
+SELECT @@SESSION.example_double_thdvar;
+
+SET SESSION example_double_thdvar = 0.4;
+SELECT @@SESSION.example_double_thdvar;
+
+SET SESSION example_double_thdvar = 123.456789;
+SELECT @@SESSION.example_double_thdvar;
+
+SET SESSION example_double_thdvar = 500;
+SELECT @@SESSION.example_double_thdvar;
+
+SET SESSION example_double_thdvar = 999.999999;
+SELECT @@SESSION.example_double_thdvar;
+
+SET SESSION example_double_thdvar = 1000.51;
+SELECT @@SESSION.example_double_thdvar;
+
+UNINSTALL PLUGIN example;

mysys/my_getopt.c

@@ -90,6 +90,35 @@ void my_getopt_register_get_addr(my_getopt_value func_addr)
   getopt_get_addr= func_addr;
 }
 
+union ull_dbl
+{
+  ulonglong ull;
+  double dbl;
+};
+
+/**
+  Returns an ulonglong value containing a raw
+  representation of the given double value.
+*/
+ulonglong getopt_double2ulonglong(double v)
+{
+  union ull_dbl u;
+  u.dbl= v;
+  compile_time_assert(sizeof(ulonglong) >= sizeof(double));
+  return u.ull;
+}
+
+/**
+  Returns the double value which corresponds to
+  the given raw representation.
+*/
+double getopt_ulonglong2double(ulonglong v)
+{
+  union ull_dbl u;
+  u.ull= v;
+  return u.dbl;
+}
+
 /**
   Handle command line options.
   Sort options.
@@ -1044,14 +1073,18 @@ double getopt_double_limit_value(double num, const struct my_option *optp,
 {
   my_bool adjusted= FALSE;
   double old= num;
-  if (optp->max_value && num > (double) optp->max_value)
+  double min, max;
+
+  max= getopt_ulonglong2double(optp->max_value);
+  min= getopt_ulonglong2double(optp->min_value);
+  if (max && num > max)
   {
-    num= (double) optp->max_value;
+    num= max;
     adjusted= TRUE;
   }
-  if (num < (double) optp->min_value)
+  if (num < min)
   {
-    num= (double) optp->min_value;
+    num= min;
     adjusted= TRUE;
   }
   if (fix)
@@ -1134,7 +1167,7 @@ static void init_one_value(const struct my_option *option, void *variable,
     *((ulonglong*) variable)= (ulonglong) value;
     break;
   case GET_DOUBLE:
-    *((double*) variable)= ulonglong2double(value);
+    *((double*) variable)= getopt_ulonglong2double(value);
     break;
   case GET_STR:
     /*

sql/sql_plugin.cc

@@ -2059,6 +2059,7 @@ typedef DECLARE_MYSQL_SYSVAR_SIMPLE(sysvar_longlong_t, longlong);
 typedef DECLARE_MYSQL_SYSVAR_SIMPLE(sysvar_uint_t, uint);
 typedef DECLARE_MYSQL_SYSVAR_SIMPLE(sysvar_ulong_t, ulong);
 typedef DECLARE_MYSQL_SYSVAR_SIMPLE(sysvar_ulonglong_t, ulonglong);
+typedef DECLARE_MYSQL_SYSVAR_SIMPLE(sysvar_double_t, double);
 
 typedef DECLARE_MYSQL_THDVAR_SIMPLE(thdvar_int_t, int);
 typedef DECLARE_MYSQL_THDVAR_SIMPLE(thdvar_long_t, long);
@@ -2066,6 +2067,7 @@ typedef DECLARE_MYSQL_THDVAR_SIMPLE(thdvar_longlong_t, longlong);
 typedef DECLARE_MYSQL_THDVAR_SIMPLE(thdvar_uint_t, uint);
 typedef DECLARE_MYSQL_THDVAR_SIMPLE(thdvar_ulong_t, ulong);
 typedef DECLARE_MYSQL_THDVAR_SIMPLE(thdvar_ulonglong_t, ulonglong);
+typedef DECLARE_MYSQL_THDVAR_SIMPLE(thdvar_double_t, double);
 
 
 /****************************************************************************
@@ -2281,6 +2283,20 @@ err:
   return 1;
 }
 
+static int check_func_double(THD *thd, struct st_mysql_sys_var *var,
+                             void *save, st_mysql_value *value)
+{
+  double v;
+  my_bool fixed;
+  struct my_option option;
+
+  value->val_real(value, &v);
+  plugin_opt_set_limits(&option, var);
+  *(double *) save= getopt_double_limit_value(v, &option, &fixed);
+
+  return throw_bounds_warning(thd, var->name, fixed, v);
+}
+
 
 static void update_func_bool(THD *thd, struct st_mysql_sys_var *var,
                              void *tgt, const void *save)
@@ -2316,6 +2332,11 @@ static void update_func_str(THD *thd, struct st_mysql_sys_var *var,
   *(char **) tgt= *(char **) save;
 }
 
+static void update_func_double(THD *thd, struct st_mysql_sys_var *var,
+                               void *tgt, const void *save)
+{
+  *(double *) tgt= *(double *) save;
+}
 
 /****************************************************************************
   System Variables support
@@ -2430,6 +2451,9 @@ static st_bookmark *register_var(const char *plugin, const char *name,
   case PLUGIN_VAR_STR:
     size= sizeof(char*);
     break;
+  case PLUGIN_VAR_DOUBLE:
+    size= sizeof(double);
+    break;
   default:
     DBUG_ASSERT(0);
     return NULL;
@@ -2641,6 +2665,11 @@ static char **mysql_sys_var_str(THD* thd, int offset)
   return (char **) intern_sys_var_ptr(thd, offset, true);
 }
 
+static double *mysql_sys_var_double(THD* thd, int offset)
+{
+  return (double *) intern_sys_var_ptr(thd, offset, true);
+}
+
 void plugin_thdvar_init(THD *thd)
 {
   plugin_ref old_table_plugin= thd->variables.table_plugin;
@@ -2773,6 +2802,8 @@ static SHOW_TYPE pluginvar_show_type(st_mysql_sys_var *plugin_var)
   case PLUGIN_VAR_ENUM:
   case PLUGIN_VAR_SET:
     return SHOW_CHAR;
+  case PLUGIN_VAR_DOUBLE:
+    return SHOW_DOUBLE;
   default:
     DBUG_ASSERT(0);
     return SHOW_UNDEF;
@@ -2923,6 +2954,8 @@ bool sys_var_pluginvar::check_update_type(Item_result type)
   case PLUGIN_VAR_BOOL:
   case PLUGIN_VAR_SET:
     return type != STRING_RESULT && type != INT_RESULT;
+  case PLUGIN_VAR_DOUBLE:
+    return type != INT_RESULT && type != REAL_RESULT && type != DECIMAL_RESULT;
   default:
     return true;
   }
@@ -3048,6 +3081,9 @@ bool sys_var_pluginvar::global_update(THD *thd, set_var *var)
     case PLUGIN_VAR_STR:
       src= &((sysvar_str_t*) plugin_var)->def_val;
       break;
+    case PLUGIN_VAR_DOUBLE:
+      src= &((sysvar_double_t*) plugin_var)->def_val;
+      break;
     case PLUGIN_VAR_INT | PLUGIN_VAR_THDLOCAL:
       src= &((thdvar_uint_t*) plugin_var)->def_val;
       break;
@@ -3069,6 +3105,9 @@ bool sys_var_pluginvar::global_update(THD *thd, set_var *var)
     case PLUGIN_VAR_STR | PLUGIN_VAR_THDLOCAL:
       src= &((thdvar_str_t*) plugin_var)->def_val;
       break;
+    case PLUGIN_VAR_DOUBLE | PLUGIN_VAR_THDLOCAL:
+      src= &((thdvar_double_t*) plugin_var)->def_val;
+      break;
     default:
       DBUG_ASSERT(0);
     }
@@ -3092,6 +3131,13 @@ bool sys_var_pluginvar::global_update(THD *thd, set_var *var)
   options->max_value= (opt)->max_val; \
   options->block_size= (long) (opt)->blk_sz
 
+#define OPTION_SET_LIMITS_DOUBLE(options, opt) \
+  options->var_type= GET_DOUBLE; \
+  options->def_value= (longlong) getopt_double2ulonglong((opt)->def_val); \
+  options->min_value= (longlong) getopt_double2ulonglong((opt)->min_val); \
+  options->max_value= getopt_double2ulonglong((opt)->max_val); \
+  options->block_size= (long) (opt)->blk_sz;
+
 
 static void plugin_opt_set_limits(struct my_option *options,
                                   const struct st_mysql_sys_var *opt)
@@ -3142,6 +3188,9 @@ static void plugin_opt_set_limits(struct my_option *options,
                         GET_STR_ALLOC : GET_STR);
     options->def_value= (intptr) ((sysvar_str_t*) opt)->def_val;
     break;
+  case PLUGIN_VAR_DOUBLE:
+    OPTION_SET_LIMITS_DOUBLE(options, (sysvar_double_t*) opt);
+    break;
   /* threadlocal variables */
   case PLUGIN_VAR_INT | PLUGIN_VAR_THDLOCAL:
     OPTION_SET_LIMITS(GET_INT, options, (thdvar_int_t*) opt);
@@ -3161,6 +3210,9 @@ static void plugin_opt_set_limits(struct my_option *options,
   case PLUGIN_VAR_LONGLONG | PLUGIN_VAR_UNSIGNED | PLUGIN_VAR_THDLOCAL:
     OPTION_SET_LIMITS(GET_ULL, options, (thdvar_ulonglong_t*) opt);
     break;
+  case PLUGIN_VAR_DOUBLE | PLUGIN_VAR_THDLOCAL:
+    OPTION_SET_LIMITS_DOUBLE(options, (thdvar_double_t*) opt);
+    break;
   case PLUGIN_VAR_ENUM | PLUGIN_VAR_THDLOCAL:
     options->var_type= GET_ENUM;
     options->typelib= ((thdvar_enum_t*) opt)->typelib;
@@ -3323,6 +3375,9 @@ static int construct_options(MEM_ROOT *mem_root, struct st_plugin_int *tmp,
     case PLUGIN_VAR_SET:
       ((thdvar_set_t *) opt)->resolve= mysql_sys_var_ulonglong;
       break;
+    case PLUGIN_VAR_DOUBLE:
+      ((thdvar_double_t *) opt)->resolve= mysql_sys_var_double;
+      break;
     default:
       sql_print_error("Unknown variable type code 0x%x in plugin '%s'.",
                       opt->flags, plugin_name);
@@ -3386,6 +3441,12 @@ static int construct_options(MEM_ROOT *mem_root, struct st_plugin_int *tmp,
       if (!opt->update)
         opt->update= update_func_longlong;
       break;
+    case PLUGIN_VAR_DOUBLE:
+      if (!opt->check)
+        opt->check= check_func_double;
+      if (!opt->update)
+        opt->update= update_func_double;
+      break;
     default:
       sql_print_error("Unknown variable type code 0x%x in plugin '%s'.",
                       opt->flags, plugin_name);

sql/sys_vars.h

@@ -729,13 +729,14 @@ public:
           const char *substitute=0,
           int parse_flag= PARSE_NORMAL)
     : sys_var(&all_sys_vars, name_arg, comment, flag_args, off, getopt.id,
-              getopt.arg_type, SHOW_DOUBLE, (longlong) double2ulonglong(def_val),
+              getopt.arg_type, SHOW_DOUBLE,
+              (longlong) getopt_double2ulonglong(def_val),
               lock, binlog_status_arg, on_check_func, on_update_func,
               substitute, parse_flag)
   {
     option.var_type= GET_DOUBLE;
-    option.min_value= (longlong) double2ulonglong(min_val);
-    option.max_value= (longlong) double2ulonglong(max_val);
+    option.min_value= (longlong) getopt_double2ulonglong(min_val);
+    option.max_value= (longlong) getopt_double2ulonglong(max_val);
     global_var(double)= (double)option.def_value;
     DBUG_ASSERT(min_val < max_val);
     DBUG_ASSERT(min_val <= def_val);
@@ -767,7 +768,7 @@ public:
   void session_save_default(THD *thd, set_var *var)
   { var->save_result.double_value= global_var(double); }
   void global_save_default(THD *thd, set_var *var)
-  { var->save_result.double_value= (double)option.def_value; }
+  { var->save_result.double_value= getopt_ulonglong2double(option.def_value); }
 };
 
 /**

storage/example/ha_example.cc

@@ -1004,6 +1004,7 @@ struct st_mysql_storage_engine example_storage_engine=
 
 static ulong srv_enum_var= 0;
 static ulong srv_ulong_var= 0;
+static double srv_double_var= 0;
 
 const char *enum_var_names[]=
 {
@@ -1038,9 +1039,34 @@ static MYSQL_SYSVAR_ULONG(
   1000,
   0);
 
+static MYSQL_SYSVAR_DOUBLE(
+  double_var,
+  srv_double_var,
+  PLUGIN_VAR_RQCMDARG,
+  "0.500000..1000.500000",
+  NULL,
+  NULL,
+  8.5,
+  0.5,
+  1000.5,
+  0);                             // reserved always 0
+
+static MYSQL_THDVAR_DOUBLE(
+  double_thdvar,
+  PLUGIN_VAR_RQCMDARG,
+  "0.500000..1000.500000",
+  NULL,
+  NULL,
+  8.5,
+  0.5,
+  1000.5,
+  0);
+
 static struct st_mysql_sys_var* example_system_variables[]= {
   MYSQL_SYSVAR(enum_var),
   MYSQL_SYSVAR(ulong_var),
+  MYSQL_SYSVAR(double_var),
+  MYSQL_SYSVAR(double_thdvar),
   NULL
 };
 
@@ -1051,8 +1077,9 @@ static int show_func_example(MYSQL_THD thd, struct st_mysql_show_var *var,
   var->type= SHOW_CHAR;
   var->value= buf; // it's of SHOW_VAR_FUNC_BUFF_SIZE bytes
   my_snprintf(buf, SHOW_VAR_FUNC_BUFF_SIZE,
-              "enum_var is %lu, ulong_var is %lu, %.6b", // %b is MySQL extension
-              srv_enum_var, srv_ulong_var, "really");
+              "enum_var is %lu, ulong_var is %lu, "
+              "double_var is %f, %.6b", // %b is a MySQL extension
+              srv_enum_var, srv_ulong_var, srv_double_var, "really");
   return 0;
 }