From 5c7c425e34a8306f70354f4910a2e686230320f4 Mon Sep 17 00:00:00 2001
From: Lars Hofhansl <larsh@apache.org>
Date: Thu, 13 Dec 2018 11:56:39 -0800
Subject: [PATCH] HBASE-21590 Optimize trySkipToNextColumn in StoreScanner a
 bit.

(cherry picked from commit 11193d7cc1f5a0a7ffb73777da7ce5c1b6af6c8c)
---
 .../hadoop/hbase/regionserver/StoreScanner.java      | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java
index be226fed047..bc457df6eac 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java
@@ -808,12 +808,16 @@ public class StoreScanner extends NonReversedNonLazyKeyValueScanner
   @VisibleForTesting
   protected boolean trySkipToNextRow(Cell cell) throws IOException {
     Cell nextCell = null;
+    // used to guard against a changed next indexed key by doing a identity comparison
+    // when the identity changes we need to compare the bytes again
+    Cell previousIndexedKey = null;
     do {
       Cell nextIndexedKey = getNextIndexedKey();
       if (nextIndexedKey != null && nextIndexedKey != KeyValueScanner.NO_NEXT_INDEXED_KEY
-          && matcher.compareKeyForNextRow(nextIndexedKey, cell) >= 0) {
+          && (nextIndexedKey == previousIndexedKey || matcher.compareKeyForNextRow(nextIndexedKey, cell) >= 0)) {
         this.heap.next();
         ++kvsScanned;
+        previousIndexedKey = nextIndexedKey;
       } else {
         return false;
       }
@@ -829,12 +833,16 @@ public class StoreScanner extends NonReversedNonLazyKeyValueScanner
   @VisibleForTesting
   protected boolean trySkipToNextColumn(Cell cell) throws IOException {
     Cell nextCell = null;
+    // used to guard against a changed next indexed key by doing a identity comparison
+    // when the identity changes we need to compare the bytes again
+    Cell previousIndexedKey = null;
     do {
       Cell nextIndexedKey = getNextIndexedKey();
       if (nextIndexedKey != null && nextIndexedKey != KeyValueScanner.NO_NEXT_INDEXED_KEY
-          && matcher.compareKeyForNextColumn(nextIndexedKey, cell) >= 0) {
+          && (nextIndexedKey == previousIndexedKey || matcher.compareKeyForNextColumn(nextIndexedKey, cell) >= 0)) {
         this.heap.next();
         ++kvsScanned;
+        previousIndexedKey = nextIndexedKey;
       } else {
         return false;
       }