Preserve overlapping file endpoint invariant

Summary:
Fix for #2833.

- In `DeleteFilesInRange`, use `GetCleanInputsWithinInterval` instead of `GetOverlappingInputs` to make sure we get a clean cut set of files to delete.
- In `GetCleanInputsWithinInterval`, support nullptr as `begin_key` or `end_key`.
- In `GetOverlappingInputsRangeBinarySearch`, move the assertion for non-empty range away from `ExtendFileRangeWithinInterval`, which should be allowed to return an empty range (via `end_index < begin_index`).
Closes https://github.com/facebook/rocksdb/pull/2843

Differential Revision: D5772387

Pulled By: ajkr

fbshipit-source-id: e554e8461823c6be82b21a9262a2da02b3957881

db/db_compaction_test.cc

@@ -1517,6 +1517,60 @@ TEST_F(DBCompactionTest, DeleteFileRange) {
   ASSERT_GT(old_num_files, new_num_files);
 }
 
+TEST_F(DBCompactionTest, DeleteFileRangeFileEndpointsOverlapBug) {
+  // regression test for #2833: groups of files whose user-keys overlap at the
+  // endpoints could be split by `DeleteFilesInRange`. This caused old data to
+  // reappear, either because a new version of the key was removed, or a range
+  // deletion was partially dropped. It could also cause non-overlapping
+  // invariant to be violated if the files dropped by DeleteFilesInRange were
+  // a subset of files that a range deletion spans.
+  const int kNumL0Files = 2;
+  const int kValSize = 8 << 10;  // 8KB
+  Options options = CurrentOptions();
+  options.level0_file_num_compaction_trigger = kNumL0Files;
+  options.target_file_size_base = 1 << 10;  // 1KB
+  DestroyAndReopen(options);
+
+  // The snapshot prevents key 1 from having its old version dropped. The low
+  // `target_file_size_base` ensures two keys will be in each output file.
+  const Snapshot* snapshot = nullptr;
+  Random rnd(301);
+  // The value indicates which flush the key belonged to, which is enough
+  // for us to determine the keys' relative ages. After L0 flushes finish,
+  // files look like:
+  //
+  // File 0: 0 -> vals[0], 1 -> vals[0]
+  // File 1:               1 -> vals[1], 2 -> vals[1]
+  //
+  // Then L0->L1 compaction happens, which outputs keys as follows:
+  //
+  // File 0: 0 -> vals[0], 1 -> vals[1]
+  // File 1:               1 -> vals[0], 2 -> vals[1]
+  //
+  // DeleteFilesInRange shouldn't be allowed to drop just file 0, as that
+  // would cause `1 -> vals[0]` (an older key) to reappear.
+  std::string vals[kNumL0Files];
+  for (int i = 0; i < kNumL0Files; ++i) {
+    vals[i] = RandomString(&rnd, kValSize);
+    Put(Key(i), vals[i]);
+    Put(Key(i + 1), vals[i]);
+    Flush();
+    if (i == 0) {
+      snapshot = db_->GetSnapshot();
+    }
+  }
+  dbfull()->TEST_WaitForCompact();
+
+  // Verify `DeleteFilesInRange` can't drop only file 0 which would cause
+  // "1 -> vals[0]" to reappear.
+  Slice begin = Key(0);
+  Slice end = Key(1);
+  ASSERT_OK(DeleteFilesInRange(db_, db_->DefaultColumnFamily(), &begin, &end));
+  ASSERT_EQ(vals[1], Get(Key(1)));
+
+  db_->ReleaseSnapshot(snapshot);
+}
+
 TEST_P(DBCompactionTestWithParam, TrivialMoveToLastLevelWithFiles) {
   int32_t trivial_move = 0;
   int32_t non_trivial_move = 0;

db/db_impl.cc

@@ -2163,25 +2163,19 @@ Status DBImpl::DeleteFilesInRange(ColumnFamilyHandle* column_family,
         end_key = &end_storage;
       }
 
-      vstorage->GetOverlappingInputs(i, begin_key, end_key, &level_files, -1,
-                                     nullptr, false);
+      vstorage->GetCleanInputsWithinInterval(i, begin_key, end_key,
+                                             &level_files, -1 /* hint_index */,
+                                             nullptr /* file_index */);
       FileMetaData* level_file;
       for (uint32_t j = 0; j < level_files.size(); j++) {
         level_file = level_files[j];
-        if (((begin == nullptr) ||
-             (cfd->internal_comparator().user_comparator()->Compare(
-                  level_file->smallest.user_key(), *begin) >= 0)) &&
-            ((end == nullptr) ||
-             (cfd->internal_comparator().user_comparator()->Compare(
-                  level_file->largest.user_key(), *end) <= 0))) {
-          if (level_file->being_compacted) {
-            continue;
-          }
-          edit.SetColumnFamily(cfd->GetID());
-          edit.DeleteFile(i, level_file->fd.GetNumber());
-          deleted_files.push_back(level_file);
-          level_file->being_compacted = true;
+        if (level_file->being_compacted) {
+          continue;
         }
+        edit.SetColumnFamily(cfd->GetID());
+        edit.DeleteFile(i, level_file->fd.GetNumber());
+        deleted_files.push_back(level_file);
+        level_file->being_compacted = true;
       }
     }
     if (edit.GetDeletedFiles().empty()) {

db/version_set.cc

@@ -1835,27 +1835,33 @@ void VersionStorageInfo::GetOverlappingInputs(
 void VersionStorageInfo::GetCleanInputsWithinInterval(
     int level, const InternalKey* begin, const InternalKey* end,
     std::vector<FileMetaData*>* inputs, int hint_index, int* file_index) const {
-  if (level >= num_non_empty_levels_) {
+  inputs->clear();
+  if (file_index) {
+    *file_index = -1;
+  }
+  if (level >= num_non_empty_levels_ || level == 0 ||
+      level_files_brief_[level].num_files == 0) {
     // this level is empty, no inputs within range
+    // also don't support clean input interval within L0
     return;
   }
 
-  inputs->clear();
   Slice user_begin, user_end;
-  if (begin != nullptr) {
+  const auto& level_files = level_files_brief_[level];
+  if (begin == nullptr) {
+    user_begin = ExtractUserKey(level_files.files[0].smallest_key);
+  } else {
     user_begin = begin->user_key();
   }
-  if (end != nullptr) {
+  if (end == nullptr) {
+    user_end = ExtractUserKey(
+        level_files.files[level_files.num_files - 1].largest_key);
+  } else {
     user_end = end->user_key();
   }
-  if (file_index) {
-    *file_index = -1;
-  }
-  if (begin != nullptr && end != nullptr && level > 0) {
-    GetOverlappingInputsRangeBinarySearch(level, user_begin, user_end, inputs,
-                                          hint_index, file_index,
-                                          true /* within_interval */);
-  }
+  GetOverlappingInputsRangeBinarySearch(level, user_begin, user_end, inputs,
+                                        hint_index, file_index,
+                                        true /* within_interval */);
 }
 
 // Store in "*inputs" all files in "level" that overlap [begin,end]
@@ -1918,8 +1924,8 @@ void VersionStorageInfo::GetOverlappingInputsRangeBinarySearch(
   } else {
     ExtendFileRangeOverlappingInterval(level, user_begin, user_end, mid,
                                        &start_index, &end_index);
+    assert(end_index >= start_index);
   }
-  assert(end_index >= start_index);
   // insert overlapping files into vector
   for (int i = start_index; i <= end_index; i++) {
     inputs->push_back(files_[level][i]);

include/rocksdb/convenience.h

@@ -325,7 +325,8 @@ void CancelAllBackgroundWork(DB* db, bool wait = false);
 
 // Delete files which are entirely in the given range
 // Could leave some keys in the range which are in files which are not
-// entirely in the range.
+// entirely in the range. Also leaves L0 files regardless of whether they're
+// in the range.
 // Snapshots before the delete might not see the data in the given range.
 Status DeleteFilesInRange(DB* db, ColumnFamilyHandle* column_family,
                           const Slice* begin, const Slice* end);