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Merge zippy.cornsilk.net:/home/cmiller/work/mysql/bug22555/my50-bug22555

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into  zippy.cornsilk.net:/home/cmiller/work/mysql/mysql-5.0-maint
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cmiller@zippy.cornsilk.net
2006-12-22 16:02:54 -05:00
parent 381a79f72c 50726b2322
commit 8ffe6fb522
5 changed files with 495 additions and 245 deletions
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20
sql/item_sum.h
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@@ -683,8 +683,10 @@ public:
double val_real();
longlong val_int()
{ /* can't be fix_fields()ed */ return (longlong) rint(val_real()); }
String *val_str(String*);
my_decimal *val_decimal(my_decimal *);
String *val_str(String *str)
{ return val_string_from_real(str); }
my_decimal *val_decimal(my_decimal *dec_buf)
{ return val_decimal_from_real(dec_buf); }
bool is_null() { update_null_value(); return null_value; }
enum_field_types field_type() const
{
@@ -706,6 +708,14 @@ public:
= (sum(ai^2) - 2*sum(a)*sum(a)/count(a) + count(a)*sum(a)^2/count(a)^2 )/count(a) =
= (sum(ai^2) - 2*sum(a)^2/count(a) + sum(a)^2/count(a) )/count(a) =
= (sum(ai^2) - sum(a)^2/count(a))/count(a)
But, this falls prey to catastrophic cancellation. Instead, use the recurrence formulas
M_{1} = x_{1}, ~ M_{k} = M_{k-1} + (x_{k} - M_{k-1}) / k newline
S_{1} = 0, ~ S_{k} = S_{k-1} + (x_{k} - M_{k-1}) times (x_{k} - M_{k}) newline
for 2 <= k <= n newline
ital variance = S_{n} / (n-1)
*/
class Item_sum_variance : public Item_sum_num
@@ -714,9 +724,8 @@ class Item_sum_variance : public Item_sum_num
public:
Item_result hybrid_type;
double sum, sum_sqr;
my_decimal dec_sum[2], dec_sqr[2];
int cur_dec;
double recurrence_m, recurrence_s; /* Used in recurrence relation. */
ulonglong count;
uint f_precision0, f_scale0;
uint f_precision1, f_scale1;
@@ -725,7 +734,7 @@ public:
uint prec_increment;
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)
hybrid_type(REAL_RESULT), count(0), sample(sample_arg)
{}
Item_sum_variance(THD *thd, Item_sum_variance *item);
enum Sumfunctype sum_func () const { return VARIANCE_FUNC; }
@@ -745,7 +754,6 @@ public:
enum Item_result result_type () const { return REAL_RESULT; }
void cleanup()
{
cur_dec= 0;
count= 0;
Item_sum_num::cleanup();
}