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

Author: cshao239

core/trino-main/src/main/java/io/trino/operator/scalar/MathFunctions.java

@@ -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;
     }
 
@@ -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);
         }

core/trino-main/src/test/java/io/trino/operator/scalar/TestMathFunctions.java

@@ -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);
 
@@ -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);