[SPARK-48712][SQL] Perf Improvement for encode with empty value or UT…

…F-8 charset

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/stringExpressions.scala

@@ -2835,7 +2835,7 @@ case class Encode(
 object Encode {
   def apply(value: Expression, charset: Expression): Encode = new Encode(value, charset)
 
-  private[expressions] final lazy val VALID_CHARSETS =
+  private[sql] final lazy val VALID_CHARSETS =
     Set("US-ASCII", "ISO-8859-1", "UTF-8", "UTF-16BE", "UTF-16LE", "UTF-16", "UTF-32")
 
   def encode(
@@ -2844,6 +2844,9 @@ object Encode {
       legacyCharsets: Boolean,
       legacyErrorAction: Boolean): Array[Byte] = {
     val toCharset = charset.toString
+    if (input.numBytes == 0 || "UTF-8".equalsIgnoreCase(toCharset)) {
+      return input.getBytes
+    }
     if (legacyCharsets || VALID_CHARSETS.contains(toCharset.toUpperCase(Locale.ROOT))) {
       val encoder = try {
         val codingErrorAction = if (legacyErrorAction) {

sql/core/benchmarks/EncodeBenchmark-results.txt

@@ -0,0 +1,6 @@
+OpenJDK 64-Bit Server VM 17.0.10+0 on Mac OS X 14.5
+Apple M2 Max
+encode:                                   Best Time(ms)   Avg Time(ms)   Stdev(ms)    Rate(M/s)   Per Row(ns)   Relative
+------------------------------------------------------------------------------------------------------------------------
+UTF-8                                             79270          79698         448          0.3        3963.5       1.0X
+

sql/core/src/test/scala/org/apache/spark/sql/execution/benchmark/EncodeBenchmark.scala

@@ -0,0 +1,68 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.benchmark
+
+import org.apache.spark.benchmark.Benchmark
+
+/**
+ * Benchmark for measuring perf of different Base64 implementations
+ * To run this benchmark:
+ * {{{
+ *   1. without sbt:
+ *      bin/spark-submit --class <this class> --jars <spark core test jar> <sql core test jar>
+ *   2. build/sbt "sql/Test/runMain <this class>"
+ *   3. generate result:
+ *      SPARK_GENERATE_BENCHMARK_FILES=1 build/sbt "sql/Test/runMain <this class>"
+ *      Results will be written to "benchmarks/EncodeBenchmark-results.txt".
+ * }}}
+ */
+object EncodeBenchmark extends SqlBasedBenchmark {
+  import spark.implicits._
+  private val N = 20L * 1000 * 1000
+
+  override def runBenchmarkSuite(mainArgs: Array[String]): Unit = {
+    withTempPath { path =>
+      // scalastyle:off nonascii
+      val exprs = Seq(
+        "",
+        "Spark",
+        "白日依山尽，黄河入海流。欲穷千里目，更上一层楼。",
+        "το Spark είναι το πιο δημοφιλές πλαίσιο επεξεργασίας μεγάλων δεδομένων παγκοσμίως",
+        "세계에서 가장 인기 있는 빅데이터 처리 프레임워크인 Spark",
+        "Sparkは世界で最も人気のあるビッグデータ処理フレームワークである。")
+      // scalastyle:off nonascii
+
+      spark.range(N).map { i =>
+        val idx = (i % 6).toInt
+        val str = exprs(idx)
+        (str, str * 3, str * 5, str * 9, "")
+      }.write.parquet(path.getCanonicalPath)
+
+      val utf8 = new Benchmark("encode", N, output = output)
+      utf8.addCase("UTF-8", 3) { _ =>
+        spark.read.parquet(path.getCanonicalPath).selectExpr(
+          "encode(_1, 'UTF-8')",
+          "encode(_2, 'UTF-8')",
+          "encode(_3, 'UTF-8')",
+          "encode(_4, 'UTF-8')",
+          "encode(_5, 'UTF-8')").noop()
+      }
+      utf8.run()
+    }
+  }
+}