Merge siva.hindu.god:/usr/home/tim/m/bk/g51

into  siva.hindu.god:/usr/home/tim/m/bk/tmp/mrg51-dec26


Makefile.am:
  Auto merged
client/mysqlbinlog.cc:
  Auto merged
configure.in:
  Auto merged
client/mysqltest.c:
  Auto merged
include/config-win.h:
  Auto merged
include/my_global.h:
  Auto merged
include/my_pthread.h:
  Auto merged
include/mysql.h:
  Auto merged
include/typelib.h:
  Auto merged
mysql-test/Makefile.am:
  Auto merged
mysql-test/r/sp.result:
  Auto merged
mysql-test/r/type_timestamp.result:
  Auto merged
mysql-test/r/warnings.result:
  Auto merged
mysys/default.c:
  Auto merged
mysys/my_wincond.c:
  Auto merged
mysys/typelib.c:
  Auto merged
server-tools/instance-manager/Makefile.am:
  Auto merged
server-tools/instance-manager/guardian.cc:
  Auto merged
server-tools/instance-manager/instance.cc:
  Auto merged
sql/field.cc:
  Auto merged
sql/item_sum.cc:
  Auto merged
sql/item_sum.h:
  Auto merged
sql/net_serv.cc:
  Auto merged
sql/opt_range.cc:
  Auto merged
sql/sql_class.h:
  Auto merged
sql/sql_parse.cc:
  Auto merged
sql/share/charsets/hebrew.xml:
  Auto merged
sql/sql_show.cc:
  Auto merged
storage/federated/ha_federated.cc:
  Auto merged
strings/conf_to_src.c:
  Auto merged
vio/viossl.c:
  Auto merged
sql/field.h:
  Manual merge
sql/log_event.cc:
  Manual merge

1 files changed, 14 insertions, 6 deletions

diff --git a/sql/item_sum.h b/sql/item_sum.h
index 7879838fa90..a0e4bfbb342 100644
--- a/sql/item_sum.h
+++ b/sql/item_sum.h
@@ -682,8 +682,10 @@ 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
   {
@@ -705,6 +707,14 @@ 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
@@ -713,9 +723,8 @@ 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;
@@ -724,7 +733,7 @@ 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; }
@@ -744,7 +753,6 @@ public:
   enum Item_result result_type () const { return REAL_RESULT; }
   void cleanup()
   {
-    cur_dec= 0;
     count= 0;
     Item_sum_num::cleanup();
   }