From 12e740bba110c6ab017c73c5ef940cce39dd45b7 Mon Sep 17 00:00:00 2001
From: Kazuaki Ishizaki <ishizaki@jp.ibm.com>
Date: Wed, 27 Sep 2017 23:19:10 +0900
Subject: [PATCH] [SPARK-22130][CORE] UTF8String.trim() scans " " twice

## What changes were proposed in this pull request?

This PR allows us to scan a string including only white space (e.g. `"     "`) once while the current implementation scans twice (right to left, and then left to right).

## How was this patch tested?

Existing test suites

Author: Kazuaki Ishizaki <ishizaki@jp.ibm.com>

Closes #19355 from kiszk/SPARK-22130.
---
 .../org/apache/spark/unsafe/types/UTF8String.java     | 11 +++++------
 .../apache/spark/unsafe/types/UTF8StringSuite.java    |  3 +++
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java b/common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
index ce4a06bde8..b0d0c44823 100644
--- a/common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
+++ b/common/unsafe/src/main/java/org/apache/spark/unsafe/types/UTF8String.java
@@ -498,17 +498,16 @@ public final class UTF8String implements Comparable<UTF8String>, Externalizable,
 
   public UTF8String trim() {
     int s = 0;
-    int e = this.numBytes - 1;
     // skip all of the space (0x20) in the left side
     while (s < this.numBytes && getByte(s) == 0x20) s++;
-    // skip all of the space (0x20) in the right side
-    while (e >= 0 && getByte(e) == 0x20) e--;
-    if (s > e) {
+    if (s == this.numBytes) {
       // empty string
       return EMPTY_UTF8;
-    } else {
-      return copyUTF8String(s, e);
     }
+    // skip all of the space (0x20) in the right side
+    int e = this.numBytes - 1;
+    while (e > s && getByte(e) == 0x20) e--;
+    return copyUTF8String(s, e);
   }
 
   /**
diff --git a/common/unsafe/src/test/java/org/apache/spark/unsafe/types/UTF8StringSuite.java b/common/unsafe/src/test/java/org/apache/spark/unsafe/types/UTF8StringSuite.java
index 7b03d2c650..9b303fa5bc 100644
--- a/common/unsafe/src/test/java/org/apache/spark/unsafe/types/UTF8StringSuite.java
+++ b/common/unsafe/src/test/java/org/apache/spark/unsafe/types/UTF8StringSuite.java
@@ -222,10 +222,13 @@ public class UTF8StringSuite {
 
   @Test
   public void trims() {
+    assertEquals(fromString("1"), fromString("1").trim());
+
     assertEquals(fromString("hello"), fromString("  hello ").trim());
     assertEquals(fromString("hello "), fromString("  hello ").trimLeft());
     assertEquals(fromString("  hello"), fromString("  hello ").trimRight());
 
+    assertEquals(EMPTY_UTF8, EMPTY_UTF8.trim());
     assertEquals(EMPTY_UTF8, fromString("  ").trim());
     assertEquals(EMPTY_UTF8, fromString("  ").trimLeft());
     assertEquals(EMPTY_UTF8, fromString("  ").trimRight());