The problem was in different representations of double variables depending on
platform/compiler/compile options. In some cases double variables are represented by
64 bits (while in memory), or by 80 bits (while in FPU register). As a result equal
values are not considered "==". As many sources point out,  doubles should not be
compared by '==' for this reason. This fix subtracts the scaled minimal double
value X such that 1 + X != 1, to ensure that the inequality holds in any case.


sql/opt_range.cc:
  Do not compare double values with == because they may have different representations.