Support for LevelDB SST with .ldb suffix

Summary:
	Handle SST files with both ".sst" and ".ldb" suffix.
	This enables user to migrate from leveldb to rocksdb.

Test Plan:
        Added unit test with DB operating on SSTs with names schema.
        See db/dc_test.cc:SSTsWithLdbSuffixHandling for details

Reviewers: yhchiang, sdong, igor

Reviewed By: igor

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D48003

HISTORY.md

@@ -4,6 +4,7 @@
 ### New Features
 * Added single delete operation as a more efficient way to delete keys that have not been overwritten.
 * Added experimental AddFile() to DB interface that allow users to add files created by SstFileWriter into an empty Database, see include/rocksdb/sst_file_writer.h and DB::AddFile() for more info.
+* Added support for opening SST files with .ldb suffix which enables opening LevelDB databases.
 
 ### Public API Changes
 * Added SingleDelete() to the DB interface.

db/db_impl.cc

@@ -4481,6 +4481,10 @@ Status DBImpl::CheckConsistency() {
 
     uint64_t fsize = 0;
     Status s = env_->GetFileSize(file_path, &fsize);
+    if (!s.ok() &&
+        env_->GetFileSize(Rocks2LevelTableFileName(file_path), &fsize).ok()) {
+      s = Status::OK();
+    }
     if (!s.ok()) {
       corruption_messages +=
           "Can't access " + md.name + ": " + s.ToString() + "\n";

db/db_test.cc

@@ -26,7 +26,6 @@
 #include "db/filename.h"
 #include "db/dbformat.h"
 #include "db/db_impl.h"
-#include "db/filename.h"
 #include "db/job_context.h"
 #include "db/version_set.h"
 #include "db/write_batch_internal.h"
@@ -9639,6 +9638,47 @@ TEST_F(DBTest, AddExternalSstFileMultiThreaded) {
                          kSkipFIFOCompaction));
 }
 
+// 1 Create some SST files by inserting K-V pairs into DB
+// 2 Close DB and change suffix from ".sst" to ".ldb" for every other SST file
+// 3 Open DB and check if all key can be read
+TEST_F(DBTest, SSTsWithLdbSuffixHandling) {
+  Options options = CurrentOptions();
+  options.write_buffer_size = 110 << 10;  // 110KB
+  options.num_levels = 4;
+  DestroyAndReopen(options);
+
+  Random rnd(301);
+  int key_id = 0;
+  for (int i = 0; i < 10; ++i) {
+    GenerateNewFile(&rnd, &key_id, false);
+  }
+  Flush();
+  Close();
+  int const num_files = GetSstFileCount(dbname_);
+  ASSERT_GT(num_files, 0);
+
+  std::vector<std::string> filenames;
+  GetSstFiles(dbname_, &filenames);
+  int num_ldb_files = 0;
+  for (unsigned int i = 0; i < filenames.size(); ++i) {
+    if (i & 1) {
+      continue;
+    }
+    std::string const rdb_name = dbname_ + "/" + filenames[i];
+    std::string const ldb_name = Rocks2LevelTableFileName(rdb_name);
+    ASSERT_TRUE(env_->RenameFile(rdb_name, ldb_name).ok());
+    ++num_ldb_files;
+  }
+  ASSERT_GT(num_ldb_files, 0);
+  ASSERT_EQ(num_files, GetSstFileCount(dbname_));
+
+  Reopen(options);
+  for (int k = 0; k < key_id; ++k) {
+    ASSERT_NE("NOT_FOUND", Get(Key(k)));
+  }
+  Destroy(options);
+}
+
 INSTANTIATE_TEST_CASE_P(DBTestWithParam, DBTestWithParam,
                         ::testing::Values(1, 4));
 

db/filename.cc

@@ -24,6 +24,9 @@
 
 namespace rocksdb {
 
+static const std::string kRocksDbTFileExt = "sst";
+static const std::string kLevelDbTFileExt = "ldb";
+
 // Given a path, flatten the path name by replacing all chars not in
 // {[0-9,a-z,A-Z,-,_,.]} with _. And append '_LOG\0' at the end.
 // Return the number of chars stored in dest not including the trailing '\0'.
@@ -78,7 +81,16 @@ std::string ArchivedLogFileName(const std::string& name, uint64_t number) {
 }
 
 std::string MakeTableFileName(const std::string& path, uint64_t number) {
-  return MakeFileName(path, number, "sst");
+  return MakeFileName(path, number, kRocksDbTFileExt.c_str());
+}
+
+std::string Rocks2LevelTableFileName(const std::string& fullname) {
+  assert(fullname.size() > kRocksDbTFileExt.size() + 1);
+  if (fullname.size() <= kRocksDbTFileExt.size() + 1) {
+    return "";
+  }
+  return fullname.substr(0, fullname.size() - kRocksDbTFileExt.size()) +
+         kLevelDbTFileExt;
 }
 
 uint64_t TableFileNameToNumber(const std::string& name) {
@@ -273,17 +285,23 @@ bool ParseFileName(const std::string& fname, uint64_t* number,
     if (!ConsumeDecimalNumber(&rest, &num)) {
       return false;
     }
+    if (rest.size() <= 1 || rest[0] != '.') {
+      return false;
+    }
+    rest.remove_prefix(1);
+
     Slice suffix = rest;
-    if (suffix == Slice(".log")) {
+    if (suffix == Slice("log")) {
       *type = kLogFile;
       if (log_type && !archive_dir_found) {
         *log_type = kAliveLogFile;
       }
     } else if (archive_dir_found) {
       return false; // Archive dir can contain only log files
-    } else if (suffix == Slice(".sst")) {
+    } else if (suffix == Slice(kRocksDbTFileExt) ||
+               suffix == Slice(kLevelDbTFileExt)) {
       *type = kTableFile;
-    } else if (suffix == Slice(".dbtmp")) {
+    } else if (suffix == Slice("dbtmp")) {
       *type = kTempFile;
     } else {
       return false;

db/filename.h

@@ -55,6 +55,10 @@ extern std::string ArchivedLogFileName(const std::string& dbname,
 
 extern std::string MakeTableFileName(const std::string& name, uint64_t number);
 
+// Return the name of sstable with LevelDB suffix
+// created from RocksDB sstable suffixed name
+extern std::string Rocks2LevelTableFileName(const std::string& fullname);
+
 // the reverse function of MakeTableFileName
 // TODO(yhchiang): could merge this function with ParseFileName()
 extern uint64_t TableFileNameToNumber(const std::string& name);

db/version_set.h

@@ -666,6 +666,7 @@ class VersionSet {
   Status GetMetadataForFile(uint64_t number, int* filelevel,
                             FileMetaData** metadata, ColumnFamilyData** cfd);
 
+  // This function doesn't support leveldb SST filenames
   void GetLiveFilesMetaData(std::vector<LiveFileMetaData> *metadata);
 
   void GetObsoleteFiles(std::vector<FileMetaData*>* files,

util/db_test_util.cc

@@ -794,19 +794,22 @@ std::string DBTestBase::DumpSSTableList() {
   return property;
 }
 
+void DBTestBase::GetSstFiles(std::string path,
+                             std::vector<std::string>* files) {
+  env_->GetChildren(path, files);
+
+  files->erase(
+      std::remove_if(files->begin(), files->end(), [](std::string name) {
+        uint64_t number;
+        FileType type;
+        return !(ParseFileName(name, &number, &type) && type == kTableFile);
+      }), files->end());
+}
+
 int DBTestBase::GetSstFileCount(std::string path) {
   std::vector<std::string> files;
-  env_->GetChildren(path, &files);
+  GetSstFiles(path, &files);
-
+  return static_cast<int>(files.size());
-  int sst_count = 0;
-  uint64_t number;
-  FileType type;
-  for (size_t i = 0; i < files.size(); i++) {
-    if (ParseFileName(files[i], &number, &type) && type == kTableFile) {
-      sst_count++;
-    }
-  }
-  return sst_count;
 }
 
 // this will generate non-overlapping files since it keeps increasing key_idx

util/db_test_util.h

@@ -618,6 +618,8 @@ class DBTestBase : public testing::Test {
 
   std::string DumpSSTableList();
 
+  void GetSstFiles(std::string path, std::vector<std::string>* files);
+
   int GetSstFileCount(std::string path);
 
   // this will generate non-overlapping files since it keeps increasing key_idx