Test cast decimal

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

Author: yuancu

integ-test/src/test/java/org/opensearch/sql/ppl/CastFunctionIT.java

@@ -274,6 +274,24 @@ public void testCastNumericSTRING() throws IOException {
     verifyDataRows(actual, rows(true));
   }
 
+  @Test
+  public void testCastDecimal() throws IOException {
+    JSONObject actual =
+        executeQuery(
+            String.format(
+                "source=%s | eval s = cast(0.99 as string), f = cast(12.9 as float), "
+                    + "d = cast(100.00 as double), i = cast(2.9 as int) "
+                    + "| fields s, f, d, i",
+                TEST_INDEX_DATATYPE_NONNUMERIC));
+    verifySchema(
+        actual,
+        schema("s", "string"),
+        schema("f", "float"),
+        schema("d", "double"),
+        schema("i", "int"));
+    verifyDataRows(actual, rows("0.99", 12.9f, 100.0d, 2));
+  }
+
   @Test
   public void testCastDate() throws IOException {
     JSONObject actual =