ARROW-6093: [Java] reduce branches in algo for first match in VectorRangeSearcher

java/algorithm/src/main/java/org/apache/arrow/algorithm/search/VectorRangeSearcher.java

@@ -44,6 +44,8 @@ public static <V extends ValueVector> int getFirstMatch(
           V targetVector, VectorValueComparator<V> comparator, V keyVector, int keyIndex) {
     comparator.attachVectors(keyVector, targetVector);
 
+    int ret = SEARCH_FAIL_RESULT;
+
     int low = 0;
     int high = targetVector.getValueCount() - 1;
 
@@ -57,30 +59,13 @@ public static <V extends ValueVector> int getFirstMatch(
         // the key is larger
         low = mid + 1;
       } else {
-        // the key equals the mid value, find the lower bound by going left-ward.
-
-        // compare with the left neighbour
-        int left = mid - 1;
-        if (left == -1) {
-          // this is the first value in the vector
-          return mid;
-        } else {
-          int leftResult = comparator.compare(keyIndex, left);
-          if (leftResult > 0) {
-            // the key is greater than the left neighbour, and equal to the current one
-            // we find it
-            return mid;
-          } else if (leftResult == 0) {
-            // the left neighbour is also equal, continue to go left
-            high = mid - 1;
-          } else {
-            // the key is larger than the left neighbour, this is not possible
-            throw new IllegalStateException("The target vector is not sorted ");
-          }
-        }
+        // an equal element is found
+        // continue to go left-ward
+        ret = mid;
+        high = mid - 1;
       }
     }
-    return SEARCH_FAIL_RESULT;
+    return ret;
   }
 
   /**
@@ -97,6 +82,8 @@ public static <V extends ValueVector> int getLastMatch(
           V targetVector, VectorValueComparator<V> comparator, V keyVector, int keyIndex) {
     comparator.attachVectors(keyVector, targetVector);
 
+    int ret = SEARCH_FAIL_RESULT;
+
     int low = 0;
     int high = targetVector.getValueCount() - 1;
 
@@ -110,29 +97,12 @@ public static <V extends ValueVector> int getLastMatch(
         // the key is larger
         low = mid + 1;
       } else {
-        // the key equals the mid value, find the upper bound by going right-ward.
-
-        // compare with the right neighbour
-        int right = mid + 1;
-        if (right == targetVector.getValueCount()) {
-          // this is the last value in the vector
-          return mid;
-        } else {
-          int rightResult = comparator.compare(keyIndex, right);
-          if (rightResult < 0) {
-            // the key is smaller than the right neighbour, and equal to the current one
-            // we find it
-            return mid;
-          } else if (rightResult == 0) {
-            // the right neighbour is also equal, continue to go right
-            low = mid + 1;
-          } else {
-            // the key is smaller than the right neighbour, this is not possible
-            throw new IllegalStateException("The target vector is not sorted ");
-          }
-        }
+        // an equal element is found,
+        // continue to go right-ward
+        ret = mid;
+        low = mid + 1;
       }
     }
-    return SEARCH_FAIL_RESULT;
+    return ret;
   }
 }

java/algorithm/src/test/java/org/apache/arrow/algorithm/search/TestVectorRangeSearcher.java

@@ -19,6 +19,9 @@
 
 import static org.junit.Assert.assertEquals;
 
+import java.util.Arrays;
+import java.util.Collection;
+
 import org.apache.arrow.algorithm.sort.DefaultVectorComparators;
 import org.apache.arrow.algorithm.sort.VectorValueComparator;
 import org.apache.arrow.memory.BufferAllocator;
@@ -28,14 +31,23 @@
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
 
 /**
  * Test cases for {@link VectorRangeSearcher}.
  */
+@RunWith(Parameterized.class)
 public class TestVectorRangeSearcher {
 
   private BufferAllocator allocator;
 
+  private int repeat;
+
+  public TestVectorRangeSearcher(int repeat) {
+    this.repeat = repeat;
+  }
+
   @Before
   public void prepare() {
     allocator = new RootAllocator(1024 * 1024);
@@ -49,7 +61,6 @@ public void shutdown() {
   @Test
   public void testGetLowerBounds() {
     final int maxValue = 100;
-    final int repeat = 5;
     try (IntVector intVector = new IntVector("int vec", allocator)) {
       // allocate vector
       intVector.allocateNew(maxValue * repeat);
@@ -79,7 +90,6 @@ public void testGetLowerBounds() {
   @Test
   public void testGetLowerBoundsNegative() {
     final int maxValue = 100;
-    final int repeat = 5;
     try (IntVector intVector = new IntVector("int vec", allocator);
     IntVector negVector = new IntVector("neg vec", allocator)) {
       // allocate vector
@@ -114,7 +124,6 @@ public void testGetLowerBoundsNegative() {
   @Test
   public void testGetUpperBounds() {
     final int maxValue = 100;
-    final int repeat = 5;
     try (IntVector intVector = new IntVector("int vec", allocator)) {
       // allocate vector
       intVector.allocateNew(maxValue * repeat);
@@ -144,7 +153,6 @@ public void testGetUpperBounds() {
   @Test
   public void testGetUpperBoundsNegative() {
     final int maxValue = 100;
-    final int repeat = 5;
     try (IntVector intVector = new IntVector("int vec", allocator);
          IntVector negVector = new IntVector("neg vec", allocator)) {
       // allocate vector
@@ -175,4 +183,14 @@ public void testGetUpperBoundsNegative() {
       }
     }
   }
+
+  @Parameterized.Parameters(name = "repeat = {0}")
+  public static Collection<Object[]> getRepeat() {
+    return Arrays.asList(
+      new Object[]{1},
+      new Object[]{2},
+      new Object[]{5},
+      new Object[]{10}
+    );
+  }
 }