From 9824acd51fb791b93c099a1a63b57604d914b31d Mon Sep 17 00:00:00 2001
From: Yu Zhang <yuzhangyu@fb.com>
Date: Wed, 8 May 2024 11:14:32 -0700
Subject: [PATCH] Fix issue that cause false alarm corruption report

---
 db/compaction/compaction_iterator.cc | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/db/compaction/compaction_iterator.cc b/db/compaction/compaction_iterator.cc
index bc19de8ec28..47fddceb2b3 100644
--- a/db/compaction/compaction_iterator.cc
+++ b/db/compaction/compaction_iterator.cc
@@ -1280,6 +1280,20 @@ void CompactionIterator::DecideOutputLevel() {
   }
 #endif  // NDEBUG
 
+  // saved_seq_for_penul_check_ is populated in `NextFromInput` when the
+  // entry's sequence number is non zero and validity context for output this
+  // entry is kSwapPreferredSeqno for use in `DecideOutputLevel`. It should be
+  // cleared out here unconditionally.
+  SequenceNumber seq_for_range_check =
+      (saved_seq_for_penul_check_.has_value() &&
+       saved_seq_for_penul_check_.value() != kMaxSequenceNumber)
+          ? saved_seq_for_penul_check_.value()
+          : ikey_.sequence;
+  saved_seq_for_penul_check_ = std::nullopt;
+  ParsedInternalKey ikey_for_range_check = ikey_;
+  if (seq_for_range_check != ikey_.sequence) {
+    ikey_for_range_check.sequence = seq_for_range_check;
+  }
   if (output_to_penultimate_level_) {
     // If it's decided to output to the penultimate level, but unsafe to do so,
     // still output to the last level. For example, moving the data from a lower
@@ -1287,16 +1301,6 @@ void CompactionIterator::DecideOutputLevel() {
     // considered unsafe, because the key may conflict with higher-level SSTs
     // not from this compaction.
     // TODO: add statistic for declined output_to_penultimate_level
-    SequenceNumber seq_for_range_check =
-        (saved_seq_for_penul_check_.has_value() &&
-         saved_seq_for_penul_check_.value() != kMaxSequenceNumber)
-            ? saved_seq_for_penul_check_.value()
-            : ikey_.sequence;
-    ParsedInternalKey ikey_for_range_check = ikey_;
-    if (seq_for_range_check != ikey_.sequence) {
-      ikey_for_range_check.sequence = seq_for_range_check;
-      saved_seq_for_penul_check_ = std::nullopt;
-    }
     bool safe_to_penultimate_level =
         compaction_->WithinPenultimateLevelOutputRange(ikey_for_range_check);
     if (!safe_to_penultimate_level) {
@@ -1310,7 +1314,7 @@ void CompactionIterator::DecideOutputLevel() {
       // snapshot is released before enabling `last_level_temperature` feature
       // We will migrate the feature to `last_level_temperature` and maybe make
       // it not dynamically changeable.
-      if (ikey_.sequence > earliest_snapshot_) {
+      if (seq_for_range_check > earliest_snapshot_) {
         status_ = Status::Corruption(
             "Unsafe to store Seq later than snapshot in the last level if "
             "per_key_placement is enabled");