fix: Reusing-Iterator reads stale keys after DeleteRange() performed (#9258)

Summary:
fix https://github.com/facebook/rocksdb/issues/9255

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9258

Reviewed By: pdillinger

Differential Revision: D34879684

Pulled By: ajkr

fbshipit-source-id: 5934f4b7524dc27ecdf1430e0456a0fc02958fc7

HISTORY.md

@@ -16,6 +16,7 @@
 * Fixed a bug that DisableManualCompaction may assert when disable an unscheduled manual compaction.
 * Fixed a potential timer crash when open close DB concurrently.
 * Fixed a race condition for `alive_log_files_` in non-two-write-queues mode. The race is between the write_thread_ in WriteToWAL() and another thread executing `FindObsoleteFiles()`. The race condition will be caught if `__glibcxx_requires_nonempty` is enabled.
+* Fixed a bug that `Iterator::Refresh()` reads stale keys after DeleteRange() performed.
 
 ### Public API changes
 * Remove BlockBasedTableOptions.hash_index_allow_collision which already takes no effect.

db/arena_wrapped_db_iter.cc

@@ -58,30 +58,55 @@ Status ArenaWrappedDBIter::Refresh() {
   uint64_t cur_sv_number = cfd_->GetSuperVersionNumber();
   TEST_SYNC_POINT("ArenaWrappedDBIter::Refresh:1");
   TEST_SYNC_POINT("ArenaWrappedDBIter::Refresh:2");
-  if (sv_number_ != cur_sv_number) {
-    Env* env = db_iter_->env();
-    db_iter_->~DBIter();
-    arena_.~Arena();
-    new (&arena_) Arena();
+  while (true) {
+    if (sv_number_ != cur_sv_number) {
+      Env* env = db_iter_->env();
+      db_iter_->~DBIter();
+      arena_.~Arena();
+      new (&arena_) Arena();
 
-    SuperVersion* sv = cfd_->GetReferencedSuperVersion(db_impl_);
-    SequenceNumber latest_seq = db_impl_->GetLatestSequenceNumber();
-    if (read_callback_) {
-      read_callback_->Refresh(latest_seq);
+      SuperVersion* sv = cfd_->GetReferencedSuperVersion(db_impl_);
+      SequenceNumber latest_seq = db_impl_->GetLatestSequenceNumber();
+      if (read_callback_) {
+        read_callback_->Refresh(latest_seq);
+      }
+      Init(env, read_options_, *(cfd_->ioptions()), sv->mutable_cf_options,
+           sv->current, latest_seq,
+           sv->mutable_cf_options.max_sequential_skip_in_iterations,
+           cur_sv_number, read_callback_, db_impl_, cfd_, expose_blob_index_,
+           allow_refresh_);
+
+      InternalIterator* internal_iter = db_impl_->NewInternalIterator(
+          read_options_, cfd_, sv, &arena_, db_iter_->GetRangeDelAggregator(),
+          latest_seq, /* allow_unprepared_value */ true);
+      SetIterUnderDBIter(internal_iter);
+      break;
+    } else {
+      SequenceNumber latest_seq = db_impl_->GetLatestSequenceNumber();
+      // Refresh range-tombstones in MemTable
+      if (!read_options_.ignore_range_deletions) {
+        SuperVersion* sv = cfd_->GetThreadLocalSuperVersion(db_impl_);
+        ReadRangeDelAggregator* range_del_agg =
+            db_iter_->GetRangeDelAggregator();
+        std::unique_ptr<FragmentedRangeTombstoneIterator> range_del_iter;
+        range_del_iter.reset(
+            sv->mem->NewRangeTombstoneIterator(read_options_, latest_seq));
+        range_del_agg->AddTombstones(std::move(range_del_iter));
+        cfd_->ReturnThreadLocalSuperVersion(sv);
+      }
+      // Refresh latest sequence number
+      db_iter_->set_sequence(latest_seq);
+      db_iter_->set_valid(false);
+      // Check again if the latest super version number is changed
+      uint64_t latest_sv_number = cfd_->GetSuperVersionNumber();
+      if (latest_sv_number != cur_sv_number) {
+        // If the super version number is changed after refreshing,
+        // fallback to Re-Init the InternalIterator
+        cur_sv_number = latest_sv_number;
+        continue;
+      }
+      break;
     }
-    Init(env, read_options_, *(cfd_->ioptions()), sv->mutable_cf_options,
-         sv->current, latest_seq,
-         sv->mutable_cf_options.max_sequential_skip_in_iterations,
-         cur_sv_number, read_callback_, db_impl_, cfd_, expose_blob_index_,
-         allow_refresh_);
-
-    InternalIterator* internal_iter = db_impl_->NewInternalIterator(
-        read_options_, cfd_, sv, &arena_, db_iter_->GetRangeDelAggregator(),
-        latest_seq, /* allow_unprepared_value */ true);
-    SetIterUnderDBIter(internal_iter);
-  } else {
-    db_iter_->set_sequence(db_impl_->GetLatestSequenceNumber());
-    db_iter_->set_valid(false);
   }
   return Status::OK();
 }

db/db_range_del_test.cc

@@ -1724,6 +1724,34 @@ TEST_F(DBRangeDelTest, OverlappedKeys) {
   ASSERT_EQ(0, NumTableFilesAtLevel(1));
 }
 
+TEST_F(DBRangeDelTest, IteratorRefresh) {
+  // Refreshing an iterator after a range tombstone is added should cause the
+  // deleted range of keys to disappear.
+  for (bool sv_changed : {false, true}) {
+    ASSERT_OK(db_->Put(WriteOptions(), "key1", "value1"));
+    ASSERT_OK(db_->Put(WriteOptions(), "key2", "value2"));
+
+    auto* iter = db_->NewIterator(ReadOptions());
+    ASSERT_OK(iter->status());
+
+    ASSERT_OK(db_->DeleteRange(WriteOptions(), db_->DefaultColumnFamily(),
+                               "key2", "key3"));
+
+    if (sv_changed) {
+      ASSERT_OK(db_->Flush(FlushOptions()));
+    }
+
+    ASSERT_OK(iter->Refresh());
+    ASSERT_OK(iter->status());
+    iter->SeekToFirst();
+    ASSERT_EQ("key1", iter->key());
+    iter->Next();
+    ASSERT_FALSE(iter->Valid());
+
+    delete iter;
+  }
+}
+
 #endif  // ROCKSDB_LITE
 
 }  // namespace ROCKSDB_NAMESPACE