[SPARK-27839][SQL] Change UTF8String.replace() to operate on UTF8 bytes

## What changes were proposed in this pull request?

This PR significantly improves the performance of `UTF8String.replace()` by performing direct replacement over UTF8 bytes instead of decoding those bytes into Java Strings.

In cases where the search string is not found (i.e. no replacements are performed, a case which I expect to be common) this new implementation performs no object allocation or memory copying.

My implementation is modeled after `commons-lang3`'s `StringUtils.replace()` method. As part of my implementation, I needed a StringBuilder / resizable buffer, so I moved `UTF8StringBuilder` from the `catalyst` package to `unsafe`.

## How was this patch tested?

Copied tests from `StringExpressionSuite` to `UTF8StringSuite` and added a couple of new cases.

To evaluate performance, I did some quick local benchmarking by running the following code in `spark-shell` (with Java 1.8.0_191):

```scala
import org.apache.spark.unsafe.types.UTF8String

def benchmark(text: String, search: String, replace: String) {
  val utf8Text = UTF8String.fromString(text)
  val utf8Search = UTF8String.fromString(search)
  val utf8Replace = UTF8String.fromString(replace)

  val start = System.currentTimeMillis
  var i = 0
  while (i < 1000 * 1000 * 100) {
    utf8Text.replace(utf8Search, utf8Replace)
    i += 1
  }
  val end = System.currentTimeMillis

  println(end - start)
}

benchmark("ABCDEFGH", "DEF", "ZZZZ")  // replacement occurs
benchmark("ABCDEFGH", "Z", "")  // no replacement occurs
```

On my laptop this took ~54 / ~40 seconds seconds before this patch's changes and ~6.5 / ~3.8 seconds afterwards.

Closes apache#24707 from JoshRosen/faster-string-replace.

Authored-by: Josh Rosen <[email protected]>
Signed-off-by: Josh Rosen <[email protected]>

sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/codegen/UTF8StringBuilder.java → common/unsafe/src/main/java/org/apache/spark/unsafe/UTF8StringBuilder.java

@@ -15,9 +15,8 @@
  * limitations under the License.
  */
 
-package org.apache.spark.sql.catalyst.expressions.codegen;
+package org.apache.spark.unsafe;
 
-import org.apache.spark.unsafe.Platform;
 import org.apache.spark.unsafe.array.ByteArrayMethods;
 import org.apache.spark.unsafe.types.UTF8String;
 
@@ -34,7 +33,18 @@ public class UTF8StringBuilder {
 
   public UTF8StringBuilder() {
     // Since initial buffer size is 16 in `StringBuilder`, we set the same size here
-    this.buffer = new byte[16];
+    this(16);
+  }
+
+  public UTF8StringBuilder(int initialSize) {
+    if (initialSize < 0) {
+      throw new IllegalArgumentException("Size must be non-negative");
+    }
+    if (initialSize > ARRAY_MAX) {
+      throw new IllegalArgumentException(
+        "Size " + initialSize + " exceeded maximum size of " + ARRAY_MAX);
+    }
+    this.buffer = new byte[initialSize];
   }
 
   // Grows the buffer by at least `neededSize`
@@ -72,6 +82,17 @@ public void append(String value) {
     append(UTF8String.fromString(value));
   }
 
+  public void appendBytes(Object base, long offset, int length) {
+    grow(length);
+    Platform.copyMemory(
+      base,
+      offset,
+      buffer,
+      cursor,
+      length);
+    cursor += length;
+  }
+
   public UTF8String build() {
     return UTF8String.fromBytes(buffer, 0, totalSize());
   }

common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java

@@ -32,6 +32,7 @@
 import com.google.common.primitives.Ints;
 
 import org.apache.spark.unsafe.Platform;
+import org.apache.spark.unsafe.UTF8StringBuilder;
 import org.apache.spark.unsafe.array.ByteArrayMethods;
 import org.apache.spark.unsafe.hash.Murmur3_x86_32;
 
@@ -1002,12 +1003,29 @@ public UTF8String[] split(UTF8String pattern, int limit) {
   }
 
   public UTF8String replace(UTF8String search, UTF8String replace) {
-    if (EMPTY_UTF8.equals(search)) {
+    // This implementation is loosely based on commons-lang3's StringUtils.replace().
+    if (numBytes == 0 || search.numBytes == 0) {
       return this;
     }
-    String replaced = toString().replace(
-      search.toString(), replace.toString());
-    return fromString(replaced);
+    // Find the first occurrence of the search string.
+    int start = 0;
+    int end = this.find(search, start);
+    if (end == -1) {
+      // Search string was not found, so string is unchanged.
+      return this;
+    }
+    // At least one match was found. Estimate space needed for result.
+    // The 16x multiplier here is chosen to match commons-lang3's implementation.
+    int increase = Math.max(0, replace.numBytes - search.numBytes) * 16;
+    final UTF8StringBuilder buf = new UTF8StringBuilder(numBytes + increase);
+    while (end != -1) {
+      buf.appendBytes(this.base, this.offset + start, end - start);
+      buf.append(replace);
+      start = end + search.numBytes;
+      end = this.find(search, start);
+    }
+    buf.appendBytes(this.base, this.offset + start, numBytes - start);
+    return buf.build();
   }
 
   // TODO: Need to use `Code Point` here instead of Char in case the character longer than 2 bytes

common/unsafe/src/test/java/org/apache/spark/unsafe/types/UTF8StringSuite.java

@@ -403,6 +403,44 @@ public void split() {
       new UTF8String[]{fromString("ab"), fromString("def,ghi,")}));
   }
 
+  @Test
+  public void replace() {
+    assertEquals(
+      fromString("re123ace"),
+      fromString("replace").replace(fromString("pl"), fromString("123")));
+    assertEquals(
+      fromString("reace"),
+      fromString("replace").replace(fromString("pl"), fromString("")));
+    assertEquals(
+      fromString("replace"),
+      fromString("replace").replace(fromString(""), fromString("123")));
+    // tests for multiple replacements
+    assertEquals(
+      fromString("a12ca12c"),
+      fromString("abcabc").replace(fromString("b"), fromString("12")));
+    assertEquals(
+      fromString("adad"),
+      fromString("abcdabcd").replace(fromString("bc"), fromString("")));
+    // tests for single character search and replacement strings
+    assertEquals(
+      fromString("AbcAbc"),
+      fromString("abcabc").replace(fromString("a"), fromString("A")));
+    assertEquals(
+      fromString("abcabc"),
+      fromString("abcabc").replace(fromString("Z"), fromString("A")));
+    // Tests with non-ASCII characters
+    assertEquals(
+      fromString("花ab界"),
+      fromString("花花世界").replace(fromString("花世"), fromString("ab")));
+    assertEquals(
+      fromString("a水c"),
+      fromString("a火c").replace(fromString("火"), fromString("水")));
+    // Tests for a large number of replacements, triggering UTF8StringBuilder resize
+    assertEquals(
+      fromString("abcd").repeat(17),
+      fromString("a").repeat(17).replace(fromString("a"), fromString("abcd")));
+  }
+
   @Test
   public void levenshteinDistance() {
     assertEquals(0, EMPTY_UTF8.levenshteinDistance(EMPTY_UTF8));

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

@@ -29,6 +29,7 @@ import org.apache.spark.sql.catalyst.expressions.codegen.Block._
 import org.apache.spark.sql.catalyst.util._
 import org.apache.spark.sql.catalyst.util.DateTimeUtils._
 import org.apache.spark.sql.types._
+import org.apache.spark.unsafe.UTF8StringBuilder
 import org.apache.spark.unsafe.types.{CalendarInterval, UTF8String}
 import org.apache.spark.unsafe.types.UTF8String.{IntWrapper, LongWrapper}
 

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

@@ -30,6 +30,7 @@ import org.apache.spark.sql.catalyst.util._
 import org.apache.spark.sql.catalyst.util.DateTimeUtils._
 import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.types._
+import org.apache.spark.unsafe.UTF8StringBuilder
 import org.apache.spark.unsafe.array.ByteArrayMethods
 import org.apache.spark.unsafe.array.ByteArrayMethods.MAX_ROUNDED_ARRAY_LENGTH
 import org.apache.spark.unsafe.types.{ByteArray, UTF8String}