updated with try catch for string parsing.

Signed-off-by: Asif Bashar <asif.bashar@gmail.com>

Author: asifabashar

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

@@ -108,7 +108,11 @@ public static String toString(int num, String format) {
 
   @Strict
   public static String toString(String str, String format) {
-    BigDecimal bd = new BigDecimal(str);
-    return toString(bd, format);
+    try {
+      BigDecimal bd = new BigDecimal(str);
+      return toString(bd, format);
+    } catch (Exception e) {
+      return null;
+    }
   }
 }

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

@@ -55,7 +55,8 @@ public void testToStringFormatNotSpecified() {
             + " fields string_value, cast_value";
     RelNode root = getRelNode(ppl);
     String expectedLogical =
-            "LogicalProject(string_value=[CAST($3):VARCHAR], cast_value=[SAFE_CAST($3)])\n  LogicalTableScan(table=[[scott, EMP]])\n";
+        "LogicalProject(string_value=[CAST($3):VARCHAR], cast_value=[SAFE_CAST($3)])\n"
+            + "  LogicalTableScan(table=[[scott, EMP]])\n";
     String expectedResult =
         "string_value=7902; cast_value=7902\n"
             + "string_value=7698; cast_value=7698\n"