Fix snapshot compaction bug

CMakeLists.txt

@@ -296,6 +296,7 @@ if(LEVELDB_BUILD_TESTS)
 
   leveldb_test("${PROJECT_SOURCE_DIR}/issues/issue178_test.cc")
   leveldb_test("${PROJECT_SOURCE_DIR}/issues/issue200_test.cc")
+  leveldb_test("${PROJECT_SOURCE_DIR}/issues/issue320_test.cc")
 
   leveldb_test("${PROJECT_SOURCE_DIR}/util/env_test.cc")
   leveldb_test("${PROJECT_SOURCE_DIR}/util/status_test.cc")

db/version_set.cc

@@ -1347,9 +1347,87 @@ Compaction* VersionSet::PickCompaction() {
   return c;
 }
 
+// find the largest key in a vector of files. returns true if files it not empty
+bool FindLargestKey(const InternalKeyComparator & icmp, const std::vector<FileMetaData*> & files, InternalKey *largestKey) {
+  if (files.empty()) {
+    return false;
+  }
+  *largestKey = files[0]->largest;
+  for (size_t i = 1; i < files.size(); ++i) {
+    FileMetaData* f = files[i];
+    if (icmp.Compare(f->largest, *largestKey) > 0) {
+      *largestKey = f->largest;
+    }
+  }
+  return true;
+}
+
+// find minimum file b2=(l2, u2) in level file for which l2 > u1 and user_key(l2) = user_key(u1)
+FileMetaData* FindSmallestBoundaryFile(const InternalKeyComparator & icmp,
+                                       const std::vector<FileMetaData*> & levelFiles,
+                                       const InternalKey & largestKey) {
+  const Comparator* user_cmp = icmp.user_comparator();
+  FileMetaData* smallestBoundaryFile = NULL;
+  for (size_t i = 0; i < levelFiles.size(); ++i) {
+    FileMetaData* f = levelFiles[i];
+    if (icmp.Compare(f->smallest, largestKey) > 0 &&
+        user_cmp->Compare(f->smallest.user_key(), largestKey.user_key()) == 0) {
+      if (smallestBoundaryFile == NULL ||
+          icmp.Compare(f->smallest, smallestBoundaryFile->smallest) < 0) {
+        smallestBoundaryFile = f;
+      }
+    }
+  }
+  return smallestBoundaryFile;
+}
+
+// If there are two blocks, b1=(l1, u1) and b2=(l2, u2) and
+// user_key(u1) = user_key(l2), and if we compact b1 but not
+// b2 then a subsequent get operation will yield an incorrect
+// result because it will return the record from b2 in level
+// i rather than from b1 because it searches level by level
+// for records matching the supplied user key.
+//
+// This function extracts the largest file b1 from compactionFiles
+// and then searches for a b2 in levelFiles for which user_key(u1) =
+// user_key(l2). If it finds such a file b2 (known as a boundary file)
+// it adds it to compactionFiles and then searches again using this
+// new upper bound.
+//
+// parameters:
+//   in     levelFiles:      list of files to search for boundary files
+//   in/out compactionFiles: list of files to extend by adding boundary files
+void AddBoundaryInputs(const InternalKeyComparator& icmp,
+                       const std::vector<FileMetaData*>& levelFiles,
+                       std::vector<FileMetaData*>* compactionFiles) {
+  InternalKey largestKey;
+
+  // find largestKey in compactionFiles, quick return if compactionFiles is
+  // empty
+  if (!FindLargestKey(icmp, *compactionFiles, &largestKey)) {
+    return;
+  }
+
+  bool continueSearching = true;
+  while (continueSearching) {
+    FileMetaData* smallestBoundaryFile =
+        FindSmallestBoundaryFile(icmp, levelFiles, largestKey);
+
+    // if a boundary file was found advance largestKey, otherwise we're done
+    if (smallestBoundaryFile != NULL) {
+      compactionFiles->push_back(smallestBoundaryFile);
+      largestKey = smallestBoundaryFile->largest;
+    } else {
+      continueSearching = false;
+    }
+  }
+}
+
 void VersionSet::SetupOtherInputs(Compaction* c) {
   const int level = c->level();
   InternalKey smallest, largest;
+
+  AddBoundaryInputs(icmp_, current_->files_[level], &c->inputs_[0]);
   GetRange(c->inputs_[0], &smallest, &largest);
 
   current_->GetOverlappingInputs(level+1, &smallest, &largest, &c->inputs_[1]);
@@ -1363,6 +1441,7 @@ void VersionSet::SetupOtherInputs(Compaction* c) {
   if (!c->inputs_[1].empty()) {
     std::vector<FileMetaData*> expanded0;
     current_->GetOverlappingInputs(level, &all_start, &all_limit, &expanded0);
+    AddBoundaryInputs(icmp_, current_->files_[level], &expanded0);
     const int64_t inputs0_size = TotalFileSize(c->inputs_[0]);
     const int64_t inputs1_size = TotalFileSize(c->inputs_[1]);
     const int64_t expanded0_size = TotalFileSize(expanded0);

db/version_set_test.cc

@@ -172,7 +172,153 @@ TEST(FindFileTest, OverlappingFiles) {
   ASSERT_TRUE(Overlaps("600", "700"));
 }
 
-}  // namespace leveldb
+void AddBoundaryInputs(const InternalKeyComparator &icmp,
+                       const std::vector<FileMetaData *> &levelFiles,
+                       std::vector<FileMetaData *> *compactionFiles);
+
+class AddBoundaryInputsTest {
+ public:
+  std::vector<FileMetaData *> levelFiles_;
+  std::vector<FileMetaData *> compactionFiles_;
+  std::vector<FileMetaData *> allFiles_;
+  InternalKeyComparator icmp_;
+
+  AddBoundaryInputsTest() : icmp_(BytewiseComparator()){};
+
+  ~AddBoundaryInputsTest() {
+    for (size_t i = 0; i < allFiles_.size(); ++i) {
+      delete allFiles_[i];
+    }
+    allFiles_.clear();
+  };
+
+  FileMetaData *CreateFileMetaData(uint64_t number, InternalKey smallest,
+                                   InternalKey largest) {
+    FileMetaData *f = new FileMetaData();
+    f->number = number;
+    f->smallest = smallest;
+    f->largest = largest;
+    allFiles_.push_back(f);
+    return f;
+  }
+};
+
+TEST(AddBoundaryInputsTest, TestEmptyFileSets) {
+  AddBoundaryInputs(icmp_, levelFiles_, &compactionFiles_);
+  ASSERT_TRUE(compactionFiles_.empty());
+  ASSERT_TRUE(levelFiles_.empty());
+}
+
+TEST(AddBoundaryInputsTest, TestEmptyLevelFiles) {
+  FileMetaData *f1 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("100", 1, kTypeValue)));
+  compactionFiles_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, levelFiles_, &compactionFiles_);
+  ASSERT_EQ(1, compactionFiles_.size());
+  ASSERT_EQ(f1, compactionFiles_[0]);
+  ASSERT_TRUE(levelFiles_.empty());
+}
+
+TEST(AddBoundaryInputsTest, TestEmptyCompactionFiles) {
+  FileMetaData *f1 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("100", 1, kTypeValue)));
+  levelFiles_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, levelFiles_, &compactionFiles_);
+  ASSERT_TRUE(compactionFiles_.empty());
+  ASSERT_EQ(1, levelFiles_.size());
+  ASSERT_EQ(f1, levelFiles_[0]);
+}
+
+TEST(AddBoundaryInputsTest, TestNoBoundaryFiles) {
+  FileMetaData *f1 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("100", 1, kTypeValue)));
+  FileMetaData *f2 =
+      CreateFileMetaData(1, InternalKey("200", 2, kTypeValue),
+                         InternalKey(InternalKey("200", 1, kTypeValue)));
+  FileMetaData *f3 =
+      CreateFileMetaData(1, InternalKey("300", 2, kTypeValue),
+                         InternalKey(InternalKey("300", 1, kTypeValue)));
+
+  levelFiles_.push_back(f3);
+  levelFiles_.push_back(f2);
+  levelFiles_.push_back(f1);
+  compactionFiles_.push_back(f2);
+  compactionFiles_.push_back(f3);
+
+  AddBoundaryInputs(icmp_, levelFiles_, &compactionFiles_);
+  ASSERT_EQ(2, compactionFiles_.size());
+}
+
+TEST(AddBoundaryInputsTest, TestOneBoundaryFiles) {
+  FileMetaData *f1 =
+      CreateFileMetaData(1, InternalKey("100", 3, kTypeValue),
+                         InternalKey(InternalKey("100", 2, kTypeValue)));
+  FileMetaData *f2 =
+      CreateFileMetaData(1, InternalKey("100", 1, kTypeValue),
+                         InternalKey(InternalKey("200", 3, kTypeValue)));
+  FileMetaData *f3 =
+      CreateFileMetaData(1, InternalKey("300", 2, kTypeValue),
+                         InternalKey(InternalKey("300", 1, kTypeValue)));
+
+  levelFiles_.push_back(f3);
+  levelFiles_.push_back(f2);
+  levelFiles_.push_back(f1);
+  compactionFiles_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, levelFiles_, &compactionFiles_);
+  ASSERT_EQ(2, compactionFiles_.size());
+  ASSERT_EQ(f1, compactionFiles_[0]);
+  ASSERT_EQ(f2, compactionFiles_[1]);
+}
+
+TEST(AddBoundaryInputsTest, TestTwoBoundaryFiles) {
+  FileMetaData *f1 =
+      CreateFileMetaData(1, InternalKey("100", 6, kTypeValue),
+                         InternalKey(InternalKey("100", 5, kTypeValue)));
+  FileMetaData *f2 =
+      CreateFileMetaData(1, InternalKey("100", 2, kTypeValue),
+                         InternalKey(InternalKey("300", 1, kTypeValue)));
+  FileMetaData *f3 =
+      CreateFileMetaData(1, InternalKey("100", 4, kTypeValue),
+                         InternalKey(InternalKey("100", 3, kTypeValue)));
+
+  levelFiles_.push_back(f2);
+  levelFiles_.push_back(f3);
+  levelFiles_.push_back(f1);
+  compactionFiles_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, levelFiles_, &compactionFiles_);
+  ASSERT_EQ(3, compactionFiles_.size());
+  ASSERT_EQ(f1, compactionFiles_[0]);
+  ASSERT_EQ(f3, compactionFiles_[1]);
+  ASSERT_EQ(f2, compactionFiles_[2]);
+}
+
+TEST(AddBoundaryInputsTest, TestDisjoinFilePointers) {
+  FileMetaData *f1 = CreateFileMetaData(1, InternalKey("100", 6, kTypeValue), InternalKey(InternalKey("100", 5, kTypeValue)));
+  FileMetaData *f2 = CreateFileMetaData(1, InternalKey("100", 6, kTypeValue), InternalKey(InternalKey("100", 5, kTypeValue)));
+  FileMetaData *f3 = CreateFileMetaData(1, InternalKey("100", 2, kTypeValue), InternalKey(InternalKey("300", 1, kTypeValue)));
+  FileMetaData *f4 = CreateFileMetaData(1, InternalKey("100", 4, kTypeValue), InternalKey(InternalKey("100", 3, kTypeValue)));
+
+  levelFiles_.push_back(f2);
+  levelFiles_.push_back(f3);
+  levelFiles_.push_back(f4);
+
+  compactionFiles_.push_back(f1);
+
+  AddBoundaryInputs(icmp_, levelFiles_, &compactionFiles_);
+  ASSERT_EQ(3, compactionFiles_.size());
+  ASSERT_EQ(f1, compactionFiles_[0]);
+  ASSERT_EQ(f4, compactionFiles_[1]);
+  ASSERT_EQ(f3, compactionFiles_[2]);
+}
+
+} // namespace leveldb
 
 int main(int argc, char** argv) {
   return leveldb::test::RunAllTests();

issues/issue320_test.cc

@@ -0,0 +1,139 @@
+// Copyright (c) 2019 The LevelDB Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file. See the AUTHORS file for names of contributors.
+#include <iostream>
+#include <sstream>
+#include <string>
+#include <map>
+#include <vector>
+#include <memory>
+
+#include <math.h>
+
+#include <leveldb/db.h>
+#include <leveldb/write_batch.h>
+#include <util/testharness.h>
+
+using namespace std;
+
+namespace leveldb {
+
+namespace {
+
+unsigned int random(unsigned int max) {
+  return std::rand() % max;
+}
+
+string newString(int32_t index) {
+  const unsigned int len = 1024;
+  char bytes[len];
+  unsigned int i = 0;
+  while (i < 8) {
+    bytes[i] = 'a' + ((index >> (4 * i)) & 0xf);
+    ++i;
+  }
+  while (i < sizeof(bytes)) {
+    bytes[i] = 'a' + random(26);
+    ++i;
+  }
+  return string(bytes, sizeof(bytes));
+}
+
+}  // namespace
+
+class Issue320 { };
+
+TEST(Issue320, Test) {
+  std::srand(0);
+
+  bool delete_before_put = false;
+  bool keep_snapshots = true;
+
+  vector<pair<string, string>*> test_map(10000, nullptr);
+  vector<Snapshot const*> snapshots(100, nullptr);
+
+  DB* db;
+  Options options;
+  options.create_if_missing = true;
+
+  std::string dbpath = test::TmpDir() + "/leveldb_issue320_test";
+  ASSERT_OK(DB::Open(options, dbpath, &db));
+
+  unsigned int target_size = 10000;
+  unsigned int num_items = 0;
+  unsigned long count = 0;
+  string key;
+  string value, old_value;
+
+  WriteOptions writeOptions;
+  ReadOptions readOptions;
+  while (count < 200000) {
+    if ((++count % 1000) == 0) {
+      cout << "count: " << count << endl;
+    }
+
+    unsigned int index = random(test_map.size());
+    WriteBatch batch;
+
+    if (test_map[index] == nullptr) {
+      num_items++;
+      test_map[index] =
+          new pair<string, string>(newString(index), newString(index));
+      batch.Put(test_map[index]->first, test_map[index]->second);
+    } else {
+      ASSERT_OK(db->Get(readOptions, test_map[index]->first, &old_value));
+      if (old_value != test_map[index]->second) {
+        cout << "ERROR incorrect value returned by Get" << endl;
+        cout << "  count=" << count << endl;
+        cout << "  old value=" << old_value << endl;
+        cout << "  test_map[index]->second=" << test_map[index]->second << endl;
+        cout << "  test_map[index]->first=" << test_map[index]->first << endl;
+        cout << "  index=" << index << endl;
+        ASSERT_EQ(old_value, test_map[index]->second);
+      }
+
+      if (num_items >= target_size && random(100) > 30) {
+        batch.Delete(test_map[index]->first);
+        delete test_map[index];
+        test_map[index] = nullptr;
+        --num_items;
+      } else {
+        test_map[index]->second = newString(index);
+        if (delete_before_put) batch.Delete(test_map[index]->first);
+        batch.Put(test_map[index]->first, test_map[index]->second);
+      }
+    }
+
+    ASSERT_OK(db->Write(writeOptions, &batch));
+
+    if (keep_snapshots && random(10) == 0) {
+      unsigned int i = random(snapshots.size());
+      if (snapshots[i] != nullptr) {
+        db->ReleaseSnapshot(snapshots[i]);
+      }
+      snapshots[i] = db->GetSnapshot();
+    }
+  }
+
+  for (Snapshot const* snapshot : snapshots) {
+    if (snapshot) {
+      db->ReleaseSnapshot(snapshot);
+    }
+  }
+
+  for (size_t i = 0; i < test_map.size(); ++i) {
+    if (test_map[i] != nullptr) {
+      delete test_map[i];
+      test_map[i] = nullptr;
+    }
+  }
+
+  delete db;
+  DestroyDB(dbpath, options);
+}
+
+}  // namespace leveldb
+
+int main(int argc, char** argv) {
+  return leveldb::test::RunAllTests();
+}