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ARROW-5964: [C++][Gandiva] Remove overflow check after rounding in BasicDecimal128::FromDouble #4894

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ARROW-5964: [C++][Gandiva] Remove overflow check after rounding in BasicDecimal128::FromDouble #4894

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eaee1ab
ARROW-5964: remove overflow check after rounding
Jul 17, 2019
8d6f37a
fix tests
Jul 17, 2019
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4 changes: 2 additions & 2 deletions cpp/src/gandiva/precompiled/decimal_ops.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -491,9 +491,9 @@ static std::array<double, DecimalTypeUtil::kMaxPrecision + 1> kDoubleScaleMultip
BasicDecimal128 FromDouble(double in, int32_t precision, int32_t scale, bool* overflow) {
// Multiply decimal with the scale
auto unscaled = in * kDoubleScaleMultipliers[scale];
DECIMAL_OVERFLOW_IF(std::isnan(unscaled), overflow);

unscaled = std::round(unscaled);
DECIMAL_OVERFLOW_IF(std::isnan(unscaled) || std::fabs(unscaled) < std::fabs(in),
overflow);

// convert scaled double to int128
int32_t sign = unscaled < 0 ? -1 : 1;
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16 changes: 14 additions & 2 deletions cpp/src/gandiva/precompiled/decimal_ops_test.cc
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Expand Up @@ -872,6 +872,12 @@ TEST_F(TestDecimalSql, FromDouble) {
std::make_tuple(DecimalScalar128{162850, 38, 4}, 16.285, false),
std::make_tuple(DecimalScalar128{1629, 38, 2}, 16.285, false),

// round up
std::make_tuple(DecimalScalar128{1, 18, 0}, 1.15470053838, false),
std::make_tuple(DecimalScalar128{-1, 18, 0}, -1.15470053838, false),
std::make_tuple(DecimalScalar128{2, 18, 0}, 1.55470053838, false),
std::make_tuple(DecimalScalar128{-2, 18, 0}, -1.55470053838, false),

// border cases
std::make_tuple(DecimalScalar128{-kMaxDoubleInt, 38, 0},
static_cast<double>(-kMaxDoubleInt), false),
Expand All @@ -887,10 +893,16 @@ TEST_F(TestDecimalSql, FromDouble) {
std::make_tuple(DecimalScalar128{1230, 38, 33}, 1.23E-30, false),
std::make_tuple(DecimalScalar128{123, 38, 38}, 1.23E-36, false),

// overflow due to very low double
// very small doubles
std::make_tuple(DecimalScalar128{0, 0, 38, 0}, std::numeric_limits<double>::min(),
false),
std::make_tuple(DecimalScalar128{0, 0, 38, 0}, -std::numeric_limits<double>::min(),
false),

// overflow due to large -ve double
std::make_tuple(DecimalScalar128{0, 0, 38, 0}, -std::numeric_limits<double>::max(),
true),
// overflow due to very high double
// overflow due to large +ve double
std::make_tuple(DecimalScalar128{0, 0, 38, 0}, std::numeric_limits<double>::max(),
true),
// overflow due to scaling up.
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