diff options
Diffstat (limited to 'sql/field.cc')
| -rw-r--r-- | sql/field.cc | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/sql/field.cc b/sql/field.cc index 922c9aba6c5..68617d0204e 100644 --- a/sql/field.cc +++ b/sql/field.cc @@ -1175,6 +1175,15 @@ inline ulonglong char_prefix_to_ulonglong(uchar *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 @@ -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); maxp= char_prefix_to_ulonglong(maxp_prefix); double n, d; - n= mp - minp; + n= safe_substract(mp, minp); if (n < 0) return 0.0; - d= maxp - minp; + d= safe_substract(maxp, minp); if (d <= 0) return 1.0; return MY_MIN(n/d, 1.0); |