Mod function should return decimal instead of float when handle the operands are decimal literal (#4407)

* Mod function should return decimal instead of float when handle the operands are decimal literal

Signed-off-by: Lantao Jin <[email protected]>

* add IT

Signed-off-by: Lantao Jin <[email protected]>

---------

Signed-off-by: Lantao Jin <[email protected]>

Author: LantaoJin

core/src/main/java/org/opensearch/sql/expression/function/udf/math/ModFunction.java

@@ -94,6 +94,9 @@ public static Number floatingMod(Number dividend, Number divisor) {
       BigDecimal b0 = new BigDecimal(dividend.toString());
       BigDecimal b1 = new BigDecimal(divisor.toString());
       BigDecimal result = b0.remainder(b1);
+      if (dividend instanceof BigDecimal || divisor instanceof BigDecimal) {
+        return result;
+      }
       return MathUtils.coerceToWidestFloatingType(dividend, divisor, result.doubleValue());
     }
   }

integ-test/src/yamlRestTest/resources/rest-api-spec/test/issues/4407.yml

@@ -0,0 +1,37 @@
+setup:
+  - do:
+      query.settings:
+        body:
+          transient:
+            plugins.calcite.enabled : true
+  - do:
+      bulk:
+        index: test
+        refresh: true
+        body:
+          - '{"index": {}}'
+          - '{"id": 3.1}'
+
+---
+teardown:
+  - do:
+      query.settings:
+        body:
+          transient:
+            plugins.calcite.enabled : false
+
+---
+"big decimal literal":
+  - skip:
+      features:
+        - headers
+        - allowed_warnings
+  - do:
+      headers:
+        Content-Type: 'application/json'
+      ppl:
+        body:
+          query: source=test | eval a = mod(3.1, 2), b = modulus(3.1, 2.0), c = mod(id, 2.0) | fields a,b,c
+
+  - match: { total: 1 }
+  - match: {"datarows": [[1.1,1.1,1.1]]}

ppl/src/test/java/org/opensearch/sql/ppl/calcite/CalcitePPLMathFunctionTest.java

@@ -237,6 +237,17 @@ public void testMod() {
     verifyPPLToSparkSQL(root, expectedSparkSql);
   }
 
+  @Test
+  public void testModDecimal() {
+    RelNode root = getRelNode("source=EMP | eval MOD = mod(3.1, 2) | fields MOD");
+    String expectedLogical =
+        "LogicalProject(MOD=[MOD(3.1:DECIMAL(2, 1), 2)])\n"
+            + "  LogicalTableScan(table=[[scott, EMP]])\n";
+    verifyLogical(root, expectedLogical);
+    String expectedSparkSql = "SELECT MOD(3.1, 2) `MOD`\nFROM `scott`.`EMP`";
+    verifyPPLToSparkSQL(root, expectedSparkSql);
+  }
+
   @Test
   public void testPi() {
     RelNode root = getRelNode("source=EMP | eval PI = pi() | fields PI");