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Sergey Petrunya 2014-03-27 14:57:53 +04:00
commit 42263a2b0a
1 changed files with 11 additions and 2 deletions
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13
sql/field.cc
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@ -1175,6 +1175,15 @@ inline ulonglong char_prefix_to_ulonglong(uchar *src)
return uint8korr(src); return uint8korr(src);
} }
/*
Compute res = a - b, without losing precision and taking care that these are
unsigned numbers.
*/
static inline double safe_substract(ulonglong a, ulonglong b)
{
return (a > b)? double(a - b) : -double(b - a);
}
/** /**
@brief @brief
@ -1227,10 +1236,10 @@ double Field::pos_in_interval_val_str(Field *min, Field *max, uint data_offset)
minp= char_prefix_to_ulonglong(minp_prefix); minp= char_prefix_to_ulonglong(minp_prefix);
maxp= char_prefix_to_ulonglong(maxp_prefix); maxp= char_prefix_to_ulonglong(maxp_prefix);
double n, d; double n, d;
n= mp - minp; n= safe_substract(mp, minp);
if (n < 0) if (n < 0)
return 0.0; return 0.0;
d= maxp - minp; d= safe_substract(maxp, minp);
if (d <= 0) if (d <= 0)
return 1.0; return 1.0;
return MY_MIN(n/d, 1.0); return MY_MIN(n/d, 1.0);