BUG#3190 fix (request for STDDEV_SAMP, VAR_SAMP).

This bug is also known as WL#1639.

mysql-test/r/func_group.result

@@ -804,3 +804,10 @@ select cast(min(ifl) as decimal(5,2)) from t3;
 cast(min(ifl) as decimal(5,2))
 1.00
 drop table t1, t2, t3;
+CREATE TABLE t1 (id int(11),value1 float(10,2));
+INSERT INTO t1 VALUES (1,0.00),(1,1.00), (1,2.00), (2,10.00), (2,11.00), (2,12.00), (2,13.00);
+select id, stddev_pop(value1), var_pop(value1), stddev_samp(value1), var_samp(value1) from t1 group by id;
+id	stddev_pop(value1)	var_pop(value1)	stddev_samp(value1)	var_samp(value1)
+1	0.816497	0.666667	1.000000	1.000000
+2	1.118034	1.250000	1.290994	1.666667
+DROP TABLE t1;

mysql-test/t/func_group.test

@@ -514,3 +514,13 @@ insert into t3 values(1), (2);
 select cast(min(ifl) as decimal(5,2)) from t3;
 
 drop table t1, t2, t3;
+
+
+#
+# BUG#3190, WL#1639: Standard Deviation STDDEV - 2 different calculations
+#
+
+CREATE TABLE t1 (id int(11),value1 float(10,2));
+INSERT INTO t1 VALUES (1,0.00),(1,1.00), (1,2.00), (2,10.00), (2,11.00), (2,12.00), (2,13.00);
+select id, stddev_pop(value1), var_pop(value1), stddev_samp(value1), var_samp(value1) from t1 group by id;
+DROP TABLE t1;

sql/item_sum.cc

@@ -853,7 +853,7 @@ Item *Item_sum_std::copy_or_same(THD* thd)
 
 Item_sum_variance::Item_sum_variance(THD *thd, Item_sum_variance *item):
   Item_sum_num(thd, item), hybrid_type(item->hybrid_type),
-    cur_dec(item->cur_dec), count(item->count)
+    cur_dec(item->cur_dec), count(item->count), sample(item->sample)
 {
   if (hybrid_type == DECIMAL_RESULT)
   {
@@ -1001,7 +1001,7 @@ double Item_sum_variance::val_real()
   if (hybrid_type == DECIMAL_RESULT)
     return val_real_from_decimal();
 
-  if (!count)
+  if (count <= sample)
   {
     null_value=1;
     return 0.0;
@@ -1009,30 +1009,31 @@ double Item_sum_variance::val_real()
   null_value=0;
   /* Avoid problems when the precision isn't good enough */
   double tmp=ulonglong2double(count);
-  double tmp2=(sum_sqr - sum*sum/tmp)/tmp;
+  double tmp2= (sum_sqr - sum*sum/tmp)/(tmp - (double)sample);
   return tmp2 <= 0.0 ? 0.0 : tmp2;
 }
 
 
 my_decimal *Item_sum_variance::val_decimal(my_decimal *dec_buf)
 {
-  my_decimal count_buf, sum_sqr_buf;
+  my_decimal count_buf, count1_buf, sum_sqr_buf;
   DBUG_ASSERT(fixed ==1 );
   if (hybrid_type == REAL_RESULT)
     return val_decimal_from_real(dec_buf);
 
-  if (!count)
+  if (count <= sample)
   {
     null_value= 1;
     return 0;
   }
   null_value= 0;
   int2my_decimal(E_DEC_FATAL_ERROR, count, 0, &count_buf);
+  int2my_decimal(E_DEC_FATAL_ERROR, count-sample, 0, &count1_buf);
   my_decimal_mul(E_DEC_FATAL_ERROR, &sum_sqr_buf,
                  dec_sum+cur_dec, dec_sum+cur_dec);
   my_decimal_div(E_DEC_FATAL_ERROR, dec_buf, &sum_sqr_buf, &count_buf, 2);
   my_decimal_sub(E_DEC_FATAL_ERROR, &sum_sqr_buf, dec_sqr+cur_dec, dec_buf);
-  my_decimal_div(E_DEC_FATAL_ERROR, dec_buf, &sum_sqr_buf, &count_buf, 2);
+  my_decimal_div(E_DEC_FATAL_ERROR, dec_buf, &sum_sqr_buf, &count1_buf, 2);
   return dec_buf;
 }
 
@@ -2004,6 +2005,7 @@ Item_variance_field::Item_variance_field(Item_sum_variance *item)
   max_length=item->max_length;
   field=item->result_field;
   maybe_null=1;
+  sample= item->sample;
   if ((hybrid_type= item->hybrid_type) == DECIMAL_RESULT)
   {
     f_scale0= item->f_scale0;
@@ -2028,11 +2030,11 @@ double Item_variance_field::val_real()
   float8get(sum_sqr,(field->ptr+sizeof(double)));
   count=sint8korr(field->ptr+sizeof(double)*2);
 
-  if ((null_value= !count))
+  if ((null_value= (count <= sample)))
     return 0.0;
 
   double tmp= (double) count;
-  double tmp2=(sum_sqr - sum*sum/tmp)/tmp;
+  double tmp2= (sum_sqr - sum*sum/tmp)/(tmp - (double)sample);
   return tmp2 <= 0.0 ? 0.0 : tmp2;
 }
 
@@ -2052,11 +2054,12 @@ my_decimal *Item_variance_field::val_decimal(my_decimal *dec_buf)
     return val_decimal_from_real(dec_buf);
 
   longlong count= sint8korr(field->ptr+dec_bin_size0+dec_bin_size1);
-  if ((null_value= !count))
+  if ((null_value= (count <= sample)))
     return 0;
 
-  my_decimal dec_count, dec_sum, dec_sqr, tmp;
+  my_decimal dec_count, dec1_count, dec_sum, dec_sqr, tmp;
   int2my_decimal(E_DEC_FATAL_ERROR, count, 0, &dec_count);
+  int2my_decimal(E_DEC_FATAL_ERROR, count-sample, 0, &dec1_count);
   binary2my_decimal(E_DEC_FATAL_ERROR, field->ptr,
                     &dec_sum, f_precision0, f_scale0);
   binary2my_decimal(E_DEC_FATAL_ERROR, field->ptr+dec_bin_size0,
@@ -2064,7 +2067,7 @@ my_decimal *Item_variance_field::val_decimal(my_decimal *dec_buf)
   my_decimal_mul(E_DEC_FATAL_ERROR, &tmp, &dec_sum, &dec_sum);
   my_decimal_div(E_DEC_FATAL_ERROR, dec_buf, &tmp, &dec_count, 2);
   my_decimal_sub(E_DEC_FATAL_ERROR, &dec_sum, &dec_sqr, dec_buf);
-  my_decimal_div(E_DEC_FATAL_ERROR, dec_buf, &dec_sum, &dec_count, 2);
+  my_decimal_div(E_DEC_FATAL_ERROR, dec_buf, &dec_sum, &dec1_count, 2);
   return dec_buf;
 }
 

sql/item_sum.h

@@ -379,6 +379,7 @@ public:
   uint f_precision0, f_scale0;
   uint f_precision1, f_scale1;
   uint dec_bin_size0, dec_bin_size1;
+  uint sample;
   Item_variance_field(Item_sum_variance *item);
   enum Type type() const {return FIELD_VARIANCE_ITEM; }
   double val_real();
@@ -422,9 +423,10 @@ public:
   uint f_precision0, f_scale0;
   uint f_precision1, f_scale1;
   uint dec_bin_size0, dec_bin_size1;
+  uint sample;
 
-  Item_sum_variance(Item *item_par) :Item_sum_num(item_par), hybrid_type(REAL_RESULT),
-    cur_dec(0),count(0)
+  Item_sum_variance(Item *item_par, uint sample_arg) :Item_sum_num(item_par),
+    hybrid_type(REAL_RESULT), cur_dec(0), count(0), sample(sample_arg)
     {}
   Item_sum_variance(THD *thd, Item_sum_variance *item);
   enum Sumfunctype sum_func () const { return VARIANCE_FUNC; }
@@ -463,7 +465,8 @@ public:
 class Item_sum_std :public Item_sum_variance
 {
   public:
-  Item_sum_std(Item *item_par) :Item_sum_variance(item_par) {}
+  Item_sum_std(Item *item_par, uint sample_arg)
+    :Item_sum_variance(item_par, sample_arg) {}
   Item_sum_std(THD *thd, Item_sum_std *item)
     :Item_sum_variance(thd, item)
     {}

sql/lex.h

@@ -735,6 +735,8 @@ static SYMBOL sql_functions[] = {
   { "STARTPOINT",	F_SYM(FUNC_ARG1),0,CREATE_FUNC_GEOM(create_func_startpoint)},
   { "STD",		SYM(STD_SYM)},
   { "STDDEV",		SYM(STD_SYM)},
+  { "STDDEV_POP",	SYM(STD_SYM)},
+  { "STDDEV_SAMP",	SYM(STDDEV_SAMP_SYM)},
   { "STR_TO_DATE",	F_SYM(FUNC_ARG2),0,CREATE_FUNC(create_func_str_to_date)},
   { "STRCMP",		F_SYM(FUNC_ARG2),0,CREATE_FUNC(create_func_strcmp)},
   { "SUBSTR",		SYM(SUBSTRING)},
@@ -760,6 +762,8 @@ static SYMBOL sql_functions[] = {
   { "UPPER",		F_SYM(FUNC_ARG1),0,CREATE_FUNC(create_func_ucase)},
   { "UUID",		F_SYM(FUNC_ARG0),0,CREATE_FUNC(create_func_uuid)},
   { "VARIANCE",		SYM(VARIANCE_SYM)},
+  { "VAR_POP",		SYM(VARIANCE_SYM)},
+  { "VAR_SAMP",		SYM(VAR_SAMP_SYM)},
   { "VERSION",		F_SYM(FUNC_ARG0),0,CREATE_FUNC(create_func_version)},
   { "WEEKDAY",		F_SYM(FUNC_ARG1),0,CREATE_FUNC(create_func_weekday)},
   { "WEEKOFYEAR",	F_SYM(FUNC_ARG1),0,CREATE_FUNC(create_func_weekofyear)},

sql/sql_yacc.yy

@@ -561,6 +561,7 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 %token  START_SYM
 %token  STATUS_SYM
 %token  STD_SYM
+%token  STDDEV_SAMP_SYM
 %token  STOP_SYM
 %token  STORAGE_SYM
 %token  STRAIGHT_JOIN
@@ -624,6 +625,7 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
 %token  UTC_DATE_SYM
 %token  UTC_TIMESTAMP_SYM
 %token  UTC_TIME_SYM
+%token  VAR_SAMP_SYM
 %token  VALUES
 %token  VALUE_SYM
 %token  VARBINARY
@@ -4754,9 +4756,13 @@ sum_expr:
 	| MAX_SYM '(' DISTINCT in_sum_expr ')'
 	  { $$=new Item_sum_max($4); }
 	| STD_SYM '(' in_sum_expr ')'
-	  { $$=new Item_sum_std($3); }
+	  { $$=new Item_sum_std($3, 0); }
 	| VARIANCE_SYM '(' in_sum_expr ')'
-	  { $$=new Item_sum_variance($3); }
+	  { $$=new Item_sum_variance($3, 0); }
+	| STDDEV_SAMP_SYM '(' in_sum_expr ')'
+	  { $$=new Item_sum_std($3, 1); }
+	| VAR_SAMP_SYM '(' in_sum_expr ')'
+	  { $$=new Item_sum_variance($3, 1); }
 	| SUM_SYM '(' in_sum_expr ')'
 	  { $$=new Item_sum_sum($3); }
 	| SUM_SYM '(' DISTINCT in_sum_expr ')'