figured types out and set it up

Author: pabloem

x-pack/plugin/esql/qa/testFixtures/src/main/resources/math.csv-spec

@@ -1844,26 +1844,26 @@ emp_no:integer | l1:double | l2:double
 ;
 
 copySignWithMixedNumericValues
-required_capability: mixed_numeric_types_in_case_copy_sign
+required_capability: mixed_numeric_types_in_case_greatest_least
 
-ROW cs1=COPY_SIGN(10.0, -5.0), cs2=COPY_SIGN(10.0, null), cs3=COPY_SIGN(1, -5.0);
+ROW cs1=COPY_SIGN(10.0, -5.0), cs2=COPY_SIGN(10, 1), cs3=COPY_SIGN(1, -5.0);
 
-cs1:double | cs2:double | cs3:long
--5.0       | null      | -1
+cs1:double | cs2:integer | cs3:integer
+-10.0       | 10      | -1
 ;
 
 copySignWithMixedNumericValuesWithMV
 required_capability: mixed_numeric_types_in_case_greatest_least
 
 FROM employees
-| EVAL cs1 = COPY_SIGN(salary, salary_change)
+| EVAL cs1 = COPY_SIGN(salary, LEAST(salary_change))
 | KEEP emp_no, salary, salary_change, cs1
 | SORT emp_no
 | LIMIT 3
 ;
 
-emp_no:integer | salary:long | salary_change:double | cs1:long
-10001          | 57305       | 1.19                | 57305
-10002          | 56371       | -7.23               | -56371
-10003          | 61805       | 4.0                 | 61805
+    emp_no:integer | salary:integer | salary_change:double | cs1:integer
+    10001          | 57305          | 1.19                 | 57305
+    10002          | 56371          | [-7.23, 11.17]       | -56371  
+    10003          | 61805          | [12.82, 14.68]       | 61805  
 ;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/scalar/math/CopySign.java

@@ -146,18 +146,23 @@ public EvalOperator.ExpressionEvaluator.Factory toEvaluator(ToEvaluator toEvalua
             throw new EsqlIllegalArgumentException("Unsupported data type [{}] for function [{}]", dataType(), NAME);
         }
         var sign = children().get(1);
-        var signFactory = toEvaluator.apply(sign);
         var magnitude = children().get(0);
-        if (sign.dataType() != dataType) {
-            // If the sign is not the same type as the magnitude, we need to convert it.
-            signFactory = Cast.cast(source(), sign.dataType(), dataType, signFactory);
-        }
-        return FACTORY_PROVIDERS.get(dataType).create(source(), toEvaluator.apply(magnitude), signFactory);
+        return FACTORY_PROVIDERS.get(dataType)
+            .create(
+                source(),
+                toEvaluator.apply(magnitude),
+                // We always cast the sign to double for processing, as the sign can be any numeric type.
+                Cast.cast(source(), sign.dataType(), DataType.DOUBLE, toEvaluator.apply(sign))
+            );
     }
 
     @Evaluator(extraName = "Float")
-    static float processFloat(float magnitude, float sign) {
-        return Math.copySign(magnitude, sign);
+    static float processFloat(float magnitude, double sign) {
+        if (sign < 0) {
+            return magnitude < 0 ? magnitude : -magnitude;
+        } else {
+            return magnitude < 0 ? -magnitude : magnitude;
+        }
     }
 
     @Evaluator(extraName = "Double")
@@ -166,20 +171,20 @@ static double processDouble(double magnitude, double sign) {
     }
 
     @Evaluator(extraName = "Long")
-    static long processLong(long magnitude, long sign) {
+    static long processLong(long magnitude, double sign) {
         if (sign < 0) {
-            return -Math.abs(magnitude);
+            return magnitude < 0 ? magnitude : -magnitude;
         } else {
-            return Math.abs(magnitude);
+            return magnitude < 0 ? -magnitude : magnitude;
         }
     }
 
     @Evaluator(extraName = "Integer")
-    static int processInteger(int magnitude, int sign) {
+    static int processInteger(int magnitude, double sign) {
         if (sign < 0) {
-            return -Math.abs(magnitude);
+            return magnitude < 0 ? magnitude : -magnitude;
         } else {
-            return Math.abs(magnitude);
+            return magnitude < 0 ? -magnitude : magnitude;
         }
     }
 }