Add trivial move support in CompactFiles API (facebook#14112)

Summary:
Support trivial move in CompactFiles API, which is not supported previously.

Pull Request resolved: facebook#14112

Test Plan: Unit test

Reviewed By: cbi42

Differential Revision: D86546150

Pulled By: xingbowang

fbshipit-source-id: 08a3ae9a055f3d3d41711403b1695f44977e6ea8

Author: Xingbo Wang

db/compact_files_test.cc

@@ -534,6 +534,232 @@ TEST_F(CompactFilesTest, GetCompactionJobInfo) {
   delete db;
 }
 
+// Helper function to generate zero-padded keys
+// e.g., MakeKey("a", 5) -> "a05", MakeKey("b", 42) -> "b42"
+static std::string MakeKey(const std::string& prefix, int index) {
+  return prefix + (index < 10 ? "0" : "") + std::to_string(index);
+}
+
+TEST_F(CompactFilesTest, TrivialMoveNonOverlappingFiles) {
+  Options options;
+  options.create_if_missing = true;
+  options.disable_auto_compactions = true;
+  options.compression = kNoCompression;
+  options.level_compaction_dynamic_level_bytes = false;
+
+  DB* db = nullptr;
+  ASSERT_OK(DestroyDB(db_name_, options));
+  Status s = DB::Open(options, db_name_, &db);
+  ASSERT_OK(s);
+  ASSERT_NE(db, nullptr);
+
+  // Create 3 non-overlapping files in L0
+  // File 1: keys [a00-a99]
+  for (int i = 0; i < 100; i++) {
+    std::string key = MakeKey("a", i);
+    ASSERT_OK(db->Put(WriteOptions(), key, "value_" + key));
+  }
+  ASSERT_OK(db->Flush(FlushOptions()));
+
+  // File 2: keys [b00-b99]
+  for (int i = 0; i < 100; i++) {
+    std::string key = MakeKey("b", i);
+    ASSERT_OK(db->Put(WriteOptions(), key, "value_" + key));
+  }
+  ASSERT_OK(db->Flush(FlushOptions()));
+
+  // File 3: keys [c00-c99]
+  for (int i = 0; i < 100; i++) {
+    std::string key = MakeKey("c", i);
+    ASSERT_OK(db->Put(WriteOptions(), key, "value_" + key));
+  }
+  ASSERT_OK(db->Flush(FlushOptions()));
+
+  // Verify files are in L0
+  ColumnFamilyMetaData meta;
+  db->GetColumnFamilyMetaData(&meta);
+  ASSERT_EQ(meta.levels[0].files.size(), 3);
+  ASSERT_EQ(meta.levels[1].files.size(), 0);
+
+  // Get L0 files
+  std::vector<std::string> l0_files;
+  for (const auto& file : meta.levels[0].files) {
+    l0_files.push_back(file.db_path + "/" + file.name);
+  }
+
+  CompactionOptions compact_option;
+  compact_option.allow_trivial_move = true;
+  // Compact all L0 files to L1 (non-overlapping in L1)
+  ASSERT_OK(db->CompactFiles(compact_option, l0_files, 1));
+
+  // Verify files are now in L1
+  db->GetColumnFamilyMetaData(&meta);
+  ASSERT_EQ(meta.levels[0].files.size(), 0);
+  ASSERT_EQ(meta.levels[1].files.size(), 3);
+
+  // Get the first file from L1 (should be the one with keys a00-a99)
+  std::string l1_file_to_move;
+  std::vector<std::string> l1_files_to_move_later;
+  uint64_t l1_file_number = 0;
+  for (const auto& file : meta.levels[1].files) {
+    if (file.smallestkey[0] == 'a') {
+      l1_file_to_move = file.db_path + "/" + file.name;
+      l1_file_number = file.file_number;
+    } else {
+      l1_files_to_move_later.push_back(file.db_path + "/" + file.name);
+    }
+  }
+  ASSERT_FALSE(l1_file_to_move.empty());
+
+  // Set up sync point to verify trivial move path is taken
+  bool trivial_move_executed = false;
+  SyncPoint::GetInstance()->SetCallBack(
+      "DBImpl::CompactFilesImpl:TrivialMove",
+      [&](void* /*arg*/) { trivial_move_executed = true; });
+  SyncPoint::GetInstance()->EnableProcessing();
+
+  // Move the file from L1 to L6 - this should be a trivial move
+  // because the file doesn't overlap with anything in L6
+  std::vector<std::string> files_to_move = {l1_file_to_move};
+  ASSERT_OK(db->CompactFiles(compact_option, files_to_move, 6));
+
+  // Verify trivial move was executed
+  ASSERT_TRUE(trivial_move_executed);
+
+  SyncPoint::GetInstance()->DisableProcessing();
+  SyncPoint::GetInstance()->ClearAllCallBacks();
+
+  // Verify the file is now in L6
+  db->GetColumnFamilyMetaData(&meta);
+  ASSERT_EQ(meta.levels[1].files.size(), 2);  // Two files remain in L1
+  ASSERT_EQ(meta.levels[6].files.size(), 1);  // One file in L6
+
+  // Verify it's the correct file in L6
+  bool found_file_in_l6 = false;
+  for (const auto& file : meta.levels[6].files) {
+    if (file.file_number == l1_file_number) {
+      found_file_in_l6 = true;
+      // Verify key range hasn't changed
+      ASSERT_EQ(file.smallestkey[0], 'a');
+      ASSERT_EQ(file.largestkey[0], 'a');
+      break;
+    }
+  }
+  ASSERT_TRUE(found_file_in_l6);
+
+  // Move the other 2 files from L1 to L6, with allow_trivial_move set to false.
+  // This will trigger a normal compaction, so the 2 files will be compacted
+  // into a single file in L6.
+  ASSERT_OK(db->CompactFiles(CompactionOptions(), l1_files_to_move_later, 6));
+
+  // Verify files in L6
+  db->GetColumnFamilyMetaData(&meta);
+  ASSERT_EQ(meta.levels[1].files.size(), 0);  // Zero files remain in L1
+  ASSERT_EQ(meta.levels[6].files.size(), 2);  // Two file in L6
+
+  // Verify data integrity - all keys should still be readable
+  for (int i = 0; i < 100; i++) {
+    std::string key = MakeKey("a", i);
+    std::string value;
+    ASSERT_OK(db->Get(ReadOptions(), key, &value));
+    ASSERT_EQ(value, "value_" + key);
+  }
+
+  delete db;
+}
+
+TEST_F(CompactFilesTest, TrivialMoveBlockedByOverlap) {
+  Options options;
+  options.create_if_missing = true;
+  options.disable_auto_compactions = true;
+  options.compression = kNoCompression;
+  options.level_compaction_dynamic_level_bytes = false;
+  options.num_levels = 7;
+
+  DB* db = nullptr;
+  ASSERT_OK(DestroyDB(db_name_, options));
+  Status s = DB::Open(options, db_name_, &db);
+  ASSERT_OK(s);
+  ASSERT_NE(db, nullptr);
+
+  // Create a file in L6 with keys [m00-m99] (wide range)
+  for (int i = 0; i < 100; i++) {
+    std::string key = MakeKey("m", i);
+    ASSERT_OK(db->Put(WriteOptions(), key, "value_" + key));
+  }
+  ASSERT_OK(db->Flush(FlushOptions()));
+
+  // Get L0 file
+  ColumnFamilyMetaData meta;
+  db->GetColumnFamilyMetaData(&meta);
+  std::vector<std::string> l0_files;
+  for (const auto& file : meta.levels[0].files) {
+    l0_files.push_back(file.db_path + "/" + file.name);
+  }
+
+  CompactionOptions compact_option;
+  compact_option.allow_trivial_move = true;
+
+  // Move to L6
+  ASSERT_OK(db->CompactFiles(compact_option, l0_files, 6));
+
+  // Now create a file in L1 with overlapping keys [m50-m60]
+  for (int i = 50; i <= 60; i++) {
+    std::string key = "m" + std::to_string(i);
+    ASSERT_OK(db->Put(WriteOptions(), key, "updated_value_" + key));
+  }
+  ASSERT_OK(db->Flush(FlushOptions()));
+
+  // Get the L0 file
+  db->GetColumnFamilyMetaData(&meta);
+  std::vector<std::string> l0_files_2;
+  for (const auto& file : meta.levels[0].files) {
+    l0_files_2.push_back(file.db_path + "/" + file.name);
+  }
+
+  // Move to L1
+  ASSERT_OK(db->CompactFiles(compact_option, l0_files_2, 1));
+
+  // Get the L1 file
+  db->GetColumnFamilyMetaData(&meta);
+  ASSERT_EQ(meta.levels[1].files.size(), 1);
+  std::string l1_file =
+      meta.levels[1].files[0].db_path + "/" + meta.levels[1].files[0].name;
+
+  // Set up sync point to verify full compaction path is taken
+  bool trivial_move_executed = false;
+  SyncPoint::GetInstance()->SetCallBack(
+      "DBImpl::CompactFilesImpl:TrivialMove",
+      [&](void* /*arg*/) { trivial_move_executed = true; });
+  SyncPoint::GetInstance()->EnableProcessing();
+
+  // Try to move from L1 to L6 - this should NOT be a trivial move
+  // because the file overlaps with the existing file in L6
+  ASSERT_OK(db->CompactFiles(compact_option, {l1_file}, 6));
+
+  // Verify trivial move was NOT executed (full compaction happened)
+  ASSERT_FALSE(trivial_move_executed);
+
+  SyncPoint::GetInstance()->DisableProcessing();
+  SyncPoint::GetInstance()->ClearAllCallBacks();
+
+  // Verify the result - should have merged data in L6
+  db->GetColumnFamilyMetaData(&meta);
+  ASSERT_EQ(meta.levels[1].files.size(), 0);  // L1 should be empty
+  // L6 should have the merged file (may be 1 file if merged, or 2 if not)
+  ASSERT_GE(meta.levels[6].files.size(), 1);
+
+  // Verify updated values are present
+  for (int i = 50; i <= 60; i++) {
+    std::string key = "m" + std::to_string(i);
+    std::string value;
+    ASSERT_OK(db->Get(ReadOptions(), key, &value));
+    ASSERT_EQ(value, "updated_value_" + key);
+  }
+
+  delete db;
+}
+
 }  // namespace ROCKSDB_NAMESPACE
 
 int main(int argc, char** argv) {

db/db_impl/db_impl.h

@@ -2396,6 +2396,14 @@ class DBImpl : public DB {
                           JobContext* job_context, LogBuffer* log_buffer,
                           CompactionJobInfo* compaction_job_info);
 
+  // Helper function to perform trivial move by updating manifest metadata
+  // without rewriting data files. This is called when IsTrivialMove() is true.
+  // REQUIRES: mutex held
+  // Returns: Status of the trivial move operation
+  Status PerformTrivialMove(Compaction& c, LogBuffer* log_buffer,
+                            bool& compaction_released, size_t& moved_files,
+                            size_t& moved_bytes);
+
   // REQUIRES: mutex unlocked
   void TrackOrUntrackFiles(const std::vector<std::string>& existing_data_files,
                            bool track);