marising commented on issue #2274: Support more column type change URL: https://github.com/apache/incubator-doris/issues/2274#issuecomment-558981844 http://www.softelectro.ru/ieee754_en.html According to the definition of IEEE754, the effect of converting a float binary to a double binary is the same as that of static_cast <double>. Data precision cannot be guaranteed, but the progress of decimal system can be guaranteed by converting a float binary to a char and then to a double. ==System== float 0.3000000 is: 0 | 01111101 | 00110011001100110011010 double 0.300000000000000 is: 0 | 01111111101 | 0011001100110011001100110011001100110011001100110011 ==Convert Binary== float 0.3000000 is: 0 | 01111101 | 00110011001100110011010 double 0.300000011920929 is: 0 | 01111111101 | 0000000000000000000001000000000000000000000000000000 ==float to char to strtod== float 0.3000000 is: 0 | 01111101 | 00110011001100110011010 double 0.300000000000000 is: 0 | 01111111101 | 0011001100110011001100110011001100110011001100110011 ==static cast== float 0.3000000 is: 0 | 01111101 | 00110011001100110011010 double 0.300000011920929 is: 0 | 01111111101 | 0000000000000000000001000000000000000000000000000000
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