Remove the magic threshold for DIVIDE and MOD

- additionally update expressions.rst to clarify how DIVIDE handles division by zero

Signed-off-by: Yuanchun Shen <yuanchu@amazon.com>

Author: yuancu

core/src/main/java/org/opensearch/sql/calcite/udf/mathUDF/DivideFunction.java

@@ -20,14 +20,15 @@ public Object eval(Object... args) {
     Number dividend = (Number) args[0];
     Number divisor = (Number) args[1];
 
-    if (Math.abs(divisor.doubleValue()) < MathUtils.EPSILON) {
+    if (divisor.doubleValue() == 0) {
       return null;
     }
 
-    double result = dividend.doubleValue() / divisor.doubleValue();
     if (MathUtils.isIntegral(dividend) && MathUtils.isIntegral(divisor)) {
-      return MathUtils.coerceToWidestIntegralType(dividend, divisor, (long) result);
+      long result = dividend.longValue() / divisor.longValue();
+      return MathUtils.coerceToWidestIntegralType(dividend, divisor, result);
     }
+    double result = dividend.doubleValue() / divisor.doubleValue();
     return MathUtils.coerceToWidestFloatingType(dividend, divisor, result);
   }
 }

core/src/main/java/org/opensearch/sql/calcite/udf/mathUDF/ModFunction.java

@@ -33,7 +33,7 @@ public Object eval(Object... args) {
               arg0.getClass().getSimpleName(), arg1.getClass().getSimpleName()));
     }
 
-    if (Math.abs(num1.doubleValue()) < MathUtils.EPSILON) {
+    if (num1.doubleValue() == 0) {
       return null;
     }
 

core/src/main/java/org/opensearch/sql/calcite/utils/MathUtils.java

@@ -6,8 +6,6 @@
 package org.opensearch.sql.calcite.utils;
 
 public class MathUtils {
-  public static final double EPSILON = 0.0000001;
-
   public static boolean isIntegral(Number n) {
     return n instanceof Byte || n instanceof Short || n instanceof Integer || n instanceof Long;
   }

docs/user/ppl/functions/expressions.rst

@@ -28,7 +28,7 @@ Arithmetic expression is an expression formed by numeric literals and binary ari
 1. ``+``: Add.
 2. ``-``: Subtract.
 3. ``*``: Multiply.
-4. ``/``: Divide. For integers, the result is an integer with fractional part discarded.
+4. ``/``: Divide. For integers, the result is an integer with fractional part discarded. Returns NULL when dividing by zero.
 5. ``%``: Modulo. This can be used with integers only with remainder of the division as result.
 
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