feat: support concat

Author: comphead

spark/src/main/scala/org/apache/comet/serde/QueryPlanSerde.scala

@@ -163,6 +163,7 @@ object QueryPlanSerde extends Logging with CometExprShim {
     classOf[BitLength] -> CometScalarFunction("bit_length"),
     classOf[Chr] -> CometScalarFunction("char"),
     classOf[ConcatWs] -> CometScalarFunction("concat_ws"),
+    classOf[Concat] -> CometScalarFunction("concat"),
     classOf[Contains] -> CometScalarFunction("contains"),
     classOf[EndsWith] -> CometScalarFunction("ends_with"),
     classOf[InitCap] -> CometInitCap,

spark/src/test/scala/org/apache/comet/CometExpressionSuite.scala

@@ -3204,4 +3204,15 @@ class CometExpressionSuite extends CometTestBase with AdaptiveSparkPlanHelper {
     }
   }
 
+  test("test concat function - strings") {
+    withTable("t1") {
+      sql(
+        "create table t1 using parquet as select uuid() c1, uuid() c2, uuid() c3, uuid() c4, cast(null as string) c5 from range(10)")
+      checkSparkAnswerAndOperator("select concat(c1, c2) AS x FROM t1")
+      checkSparkAnswerAndOperator("select concat(c1, c2, c3) AS x FROM t1")
+      checkSparkAnswerAndOperator("select concat(c1, c2, c3, c5) AS x FROM t1")
+      //checkSparkAnswerAndOperator("select concat(concat(c1, c2, c3), concat(c1, c3)) AS x FROM t1")
+    }
+  }
+
 }