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Fix an edge case with Round function when the scaled number exceeds Double.MAX_VALUE #16876

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Merged
martint merged 1 commit into from
May 1, 2023
Merged

Fix an edge case with Round function when the scaled number exceeds Double.MAX_VALUE #16876

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12 changes: 12 additions & 0 deletions core/trino-main/src/main/java/io/trino/operator/scalar/MathFunctions.java
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Original file line number Diff line number Diff line change
Expand Up @@ -837,6 +837,13 @@ public static double round(@SqlType(StandardTypes.DOUBLE) double num, @SqlType(S
if (rescaledRound != Long.MAX_VALUE) {
return sign * (rescaledRound / factor);
}
if (Double.isInfinite(rescaled)) {
// num has max 17 precisions, so to make round actually do something, decimals must be smaller than 17.
// then factor must be smaller than 10^17
// then in order for rescaled to be greater than Double.MAX_VALUE, num must be greater than 1.8E291 with many trailing zeros
// in which case, rounding is no op anyway
return num;
}
return sign * DoubleMath.roundToBigInteger(rescaled, RoundingMode.HALF_UP).doubleValue() / factor;
}

Expand All @@ -858,6 +865,11 @@ public static long roundReal(@SqlType(StandardTypes.REAL) long num, @SqlType(Sta
if (rescaledRound != Long.MAX_VALUE) {
result = sign * (rescaledRound / factor);
}
else if (Double.isInfinite(rescaled)) {
// numInFloat is max at 3.4028235e+38f, to make rescale greater than Double.MAX_VALUE, decimals must be greater than 270
// but numInFloat has max 8 precision, so rounding is no op
return num;
}
else {
result = sign * (DoubleMath.roundToBigInteger(rescaled, RoundingMode.HALF_UP).doubleValue() / factor);
}
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14 changes: 14 additions & 0 deletions core/trino-main/src/test/java/io/trino/operator/scalar/TestMathFunctions.java
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Original file line number Diff line number Diff line change
Expand Up @@ -1658,6 +1658,13 @@ public void testRound()
assertThat(assertions.function("round", "DOUBLE '3000.1234567890123456789'", "16"))
.isEqualTo(3000.1234567890124);

// 1.8E292*10^16 is infinity.
assertThat(assertions.function("round", "DOUBLE '1.8E292'", "16"))
.isEqualTo(1.8E292);

assertThat(assertions.function("round", "DOUBLE '-1.8E292'", "16"))
.isEqualTo(-1.8E292);

assertThat(assertions.function("round", "TINYINT '3'", "TINYINT '1'"))
.isEqualTo((byte) 3);

Expand Down Expand Up @@ -1702,6 +1709,13 @@ public void testRound()
assertThat(assertions.function("round", "REAL '3000.1234567890123456789'", "16"))
.isEqualTo(3000.1235f);

// 3.4028235e+38 * 10 ^ 271 is infinity
assertThat(assertions.function("round", "REAL '3.4028235e+38'", "271"))
.isEqualTo(3.4028235e+38f);

assertThat(assertions.function("round", "REAL '-3.4028235e+38'", "271"))
.isEqualTo(-3.4028235e+38f);

assertThat(assertions.function("round", "3", "1"))
.isEqualTo(3);

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