From ebe89ef9d84cf1a05a47b8d03c7509f9f103ad10 Mon Sep 17 00:00:00 2001
From: Andrew Kryczka <andrew.kryczka2@gmail.com>
Date: Tue, 4 Jun 2019 10:17:24 -0700
Subject: [PATCH] Fix merging range tombstone covering put during
 flush/compaction (#5406)

Summary:
Flush/compaction use `MergeUntil` which has a special code path to
handle a merge ending with a non-`Merge` point key. In particular if
that key is a `Put` we forgot to check whether it is covered by a range
tombstone. If it is covered then we must not include it in the following call
to `TimedFullMerge`.

Fixes #5392.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5406

Differential Revision: D15611144

Pulled By: sagar0

fbshipit-source-id: ba6a7863ca2d043f591de78fd0c4f4561f0c500e
---
 HISTORY.md              |  1 +
 db/db_range_del_test.cc | 24 ++++++++++++++++++++++++
 db/merge_helper.cc      | 10 +++++++++-
 3 files changed, 34 insertions(+), 1 deletion(-)

diff --git a/HISTORY.md b/HISTORY.md
index b9b6998c6..b3c2ef14a 100644
--- a/HISTORY.md
+++ b/HISTORY.md
@@ -24,6 +24,7 @@
 
 ### Bug Fixes
 * Fix a bug in WAL replay of secondary instance by skipping write batches with older sequence numbers than the current last sequence number.
+* Fix flush's/compaction's merge processing logic which allowed `Put`s covered by range tombstones to reappear. Note `Put`s may exist even if the user only ever called `Merge()` due to an internal conversion during compaction to the bottommost level.
 
 ## 6.2.0 (4/30/2019)
 ### New Features
diff --git a/db/db_range_del_test.cc b/db/db_range_del_test.cc
index 16d682fc0..e58095b2d 100644
--- a/db/db_range_del_test.cc
+++ b/db/db_range_del_test.cc
@@ -491,6 +491,30 @@ TEST_F(DBRangeDelTest, CompactionRemovesCoveredMergeOperands) {
   ASSERT_EQ(expected, actual);
 }
 
+TEST_F(DBRangeDelTest, PutDeleteRangeMergeFlush) {
+  // Test the sequence of operations: (1) Put, (2) DeleteRange, (3) Merge, (4)
+  // Flush. The `CompactionIterator` previously had a bug where we forgot to
+  // check for covering range tombstones when processing the (1) Put, causing
+  // it to reappear after the flush.
+  Options opts = CurrentOptions();
+  opts.merge_operator = MergeOperators::CreateUInt64AddOperator();
+  Reopen(opts);
+
+  std::string val;
+  PutFixed64(&val, 1);
+  ASSERT_OK(db_->Put(WriteOptions(), "key", val));
+  ASSERT_OK(db_->DeleteRange(WriteOptions(), db_->DefaultColumnFamily(),
+                             "key", "key_"));
+  ASSERT_OK(db_->Merge(WriteOptions(), "key", val));
+  ASSERT_OK(db_->Flush(FlushOptions()));
+
+  ReadOptions read_opts;
+  std::string expected, actual;
+  ASSERT_OK(db_->Get(read_opts, "key", &actual));
+  PutFixed64(&expected, 1);
+  ASSERT_EQ(expected, actual);
+}
+
 // NumTableFilesAtLevel() is not supported in ROCKSDB_LITE
 #ifndef ROCKSDB_LITE
 TEST_F(DBRangeDelTest, ObsoleteTombstoneCleanup) {
diff --git a/db/merge_helper.cc b/db/merge_helper.cc
index 4a4d2fb71..b5ae924ff 100644
--- a/db/merge_helper.cc
+++ b/db/merge_helper.cc
@@ -201,7 +201,15 @@ Status MergeHelper::MergeUntil(InternalIterator* iter,
       // want. Also if we're in compaction and it's a put, it would be nice to
       // run compaction filter on it.
       const Slice val = iter->value();
-      const Slice* val_ptr = (kTypeValue == ikey.type) ? &val : nullptr;
+      const Slice* val_ptr;
+      if (kTypeValue == ikey.type &&
+          (range_del_agg == nullptr ||
+           !range_del_agg->ShouldDelete(
+               ikey, RangeDelPositioningMode::kForwardTraversal))) {
+        val_ptr = &val;
+      } else {
+        val_ptr = nullptr;
+      }
       std::string merge_result;
       s = TimedFullMerge(user_merge_operator_, ikey.user_key, val_ptr,
                          merge_context_.GetOperands(), &merge_result, logger_,