Logically strip timestamp during flush (#11557)

Summary:
Logically strip the user-defined timestamp when L0 files are created during flush when `AdvancedColumnFamilyOptions.persist_user_defined_timestamps` is false. Logically stripping timestamp here means replacing the original user-defined timestamp with a mininum timestamp, which for now is hard coded to be all zeros bytes.

While working on this, I caught a missing piece on the `BlockBuilder` level for this feature. The current quick path `std::min(buffer_size, last_key_size)` needs a bit tweaking to work for this feature. When user-defined timestamp is stripped during block building, on writing first entry or right after resetting, `buffer` is empty and `buffer_size` is zero as usual. However, in follow-up writes, depending on the size of the stripped user-defined timestamp, and the size of the value, what's in `buffer` can sometimes be smaller than `last_key_size`, leading `std::min(buffer_size, last_key_size)` to truncate the `last_key`. Previous test doesn't caught the bug because in those tests, the size of the stripped user-defined timestamps bytes is smaller than the length of the value. In order to avoid the conditional operation, this PR changed the original trivial `std::min` operation into an arithmetic operation. Since this is a change in a hot and performance critical path, I did the following benchmark to check no observable regression is introduced.
```TEST_TMPDIR=/dev/shm/rocksdb1 ./db_bench -benchmarks=fillseq -memtablerep=vector -allow_concurrent_memtable_write=false -num=50000000```
Compiled with DEBUG_LEVEL=0
Test vs. control runs simulaneous for better accuracy, units = ops/sec
                       PR  vs base:
Round 1: 350652 vs 349055
Round 2: 365733 vs 364308
Round 3: 355681 vs 354475

Pull Request resolved: #11557

Test Plan:
New timestamp specific test added or existing tests augmented, both are parameterized with `UserDefinedTimestampTestMode`:
`UserDefinedTimestampTestMode::kNormal` -> UDT feature enabled, write / read with min timestamp
`UserDefinedTimestampTestMode::kStripUserDefinedTimestamps` -> UDT feature enabled, write / read with min timestamp, set Options.persist_user_defined_timestamps to false.

```
make all check
./db_wal_test --gtest_filter="*WithTimestamp*"
./flush_job_test --gtest_filter="*WithTimestamp*"
./repair_test --gtest_filter="*WithTimestamp*"
./block_based_table_reader_test
```

Reviewed By: pdillinger

Differential Revision: D47027664

Pulled By: jowlyzhang

fbshipit-source-id: e729193b6334dfc63aaa736d684d907a022571f5

db/builder.cc

@@ -15,6 +15,7 @@
 
 #include "db/blob/blob_file_builder.h"
 #include "db/compaction/compaction_iterator.h"
+#include "db/dbformat.h"
 #include "db/event_helpers.h"
 #include "db/internal_stats.h"
 #include "db/merge_helper.h"
@@ -205,21 +206,38 @@ Status BuildTable(
         /*compaction=*/nullptr, compaction_filter.get(),
         /*shutting_down=*/nullptr, db_options.info_log, full_history_ts_low);
 
+    const size_t ts_sz = ucmp->timestamp_size();
+    const bool strip_timestamp =
+        ts_sz > 0 && !ioptions.persist_user_defined_timestamps;
+
+    std::string key_after_flush_buf;
     c_iter.SeekToFirst();
     for (; c_iter.Valid(); c_iter.Next()) {
       const Slice& key = c_iter.key();
       const Slice& value = c_iter.value();
       const ParsedInternalKey& ikey = c_iter.ikey();
-      // Generate a rolling 64-bit hash of the key and values
-      // Note :
-      // Here "key" integrates 'sequence_number'+'kType'+'user key'.
-      s = output_validator.Add(key, value);
+      Slice key_after_flush = key;
+      // If user defined timestamps will be stripped from user key after flush,
+      // the in memory version of the key act logically the same as one with a
+      // minimum timestamp. We update the timestamp here so file boundary and
+      // output validator, block builder all see the effect of the stripping.
+      if (strip_timestamp) {
+        key_after_flush_buf.clear();
+        ReplaceInternalKeyWithMinTimestamp(&key_after_flush_buf, key, ts_sz);
+        key_after_flush = key_after_flush_buf;
+      }
+
+      //  Generate a rolling 64-bit hash of the key and values
+      //  Note :
+      //  Here "key" integrates 'sequence_number'+'kType'+'user key'.
+      s = output_validator.Add(key_after_flush, value);
       if (!s.ok()) {
         break;
       }
-      builder->Add(key, value);
+      builder->Add(key_after_flush, value);
 
-      s = meta->UpdateBoundaries(key, value, ikey.sequence, ikey.type);
+      s = meta->UpdateBoundaries(key_after_flush, value, ikey.sequence,
+                                 ikey.type);
       if (!s.ok()) {
         break;
       }
@@ -244,6 +262,7 @@ Status BuildTable(
            range_del_it->Next()) {
         auto tombstone = range_del_it->Tombstone();
         auto kv = tombstone.Serialize();
+        // TODO(yuzhangyu): handle range deletion for UDT in memtables only.
         builder->Add(kv.first.Encode(), kv.second);
         InternalKey tombstone_end = tombstone.SerializeEndKey();
         meta->UpdateBoundariesForRange(kv.first, tombstone_end, tombstone.seq_,
@@ -354,6 +373,8 @@ Status BuildTable(
       s = *io_status;
     }
 
+    // TODO(yuzhangyu): handle the key copy in the blob when ts should be
+    // stripped.
     if (blob_file_builder) {
       if (s.ok()) {
         s = blob_file_builder->Finish();

db/db_wal_test.cc

@@ -311,7 +311,9 @@ TEST_F(DBWALTest, Recover) {
   } while (ChangeWalOptions());
 }
 
-class DBWALTestWithTimestamp : public DBBasicTestWithTimestampBase {
+class DBWALTestWithTimestamp
+    : public DBBasicTestWithTimestampBase,
+      public testing::WithParamInterface<test::UserDefinedTimestampTestMode> {
  public:
   DBWALTestWithTimestamp()
       : DBBasicTestWithTimestampBase("db_wal_test_with_timestamp") {}
@@ -401,6 +403,54 @@ TEST_F(DBWALTestWithTimestamp, RecoverInconsistentTimestamp) {
       ReopenColumnFamiliesWithTs({"pikachu"}, ts_options).IsInvalidArgument());
 }
 
+TEST_P(DBWALTestWithTimestamp, RecoverAndFlush) {
+  // Set up the option that enables user defined timestmp size.
+  std::string min_ts = Timestamp(0, 0);
+  std::string write_ts = Timestamp(1, 0);
+  const size_t kTimestampSize = write_ts.size();
+  TestComparator test_cmp(kTimestampSize);
+  Options ts_options;
+  ts_options.create_if_missing = true;
+  ts_options.comparator = &test_cmp;
+  bool persist_udt = test::ShouldPersistUDT(GetParam());
+  ts_options.persist_user_defined_timestamps = persist_udt;
+
+  std::string smallest_ukey_without_ts = "baz";
+  std::string largest_ukey_without_ts = "foo";
+
+  ASSERT_OK(CreateAndReopenWithCFWithTs({"pikachu"}, ts_options));
+  ASSERT_OK(Put(1, largest_ukey_without_ts, write_ts, "v1"));
+  ASSERT_OK(Put(1, smallest_ukey_without_ts, write_ts, "v5"));
+
+  // Very small write buffer size to force flush memtables recovered from WAL.
+  ts_options.write_buffer_size = 16;
+  ts_options.arena_block_size = 16;
+  ASSERT_OK(ReopenColumnFamiliesWithTs({"pikachu"}, ts_options));
+  ASSERT_EQ(GetNumberOfSstFilesForColumnFamily(db_, "pikachu"),
+            static_cast<uint64_t>(1));
+
+  std::vector<std::vector<FileMetaData>> level_to_files;
+  dbfull()->TEST_GetFilesMetaData(handles_[1], &level_to_files);
+  ASSERT_GT(level_to_files.size(), 1);
+  // L0 only has one SST file.
+  ASSERT_EQ(level_to_files[0].size(), 1);
+  auto meta = level_to_files[0][0];
+  if (persist_udt) {
+    ASSERT_EQ(smallest_ukey_without_ts + write_ts, meta.smallest.user_key());
+    ASSERT_EQ(largest_ukey_without_ts + write_ts, meta.largest.user_key());
+  } else {
+    ASSERT_EQ(smallest_ukey_without_ts + min_ts, meta.smallest.user_key());
+    ASSERT_EQ(largest_ukey_without_ts + min_ts, meta.largest.user_key());
+  }
+}
+
+// Param 0: test mode for the user-defined timestamp feature
+INSTANTIATE_TEST_CASE_P(
+    RecoverAndFlush, DBWALTestWithTimestamp,
+    ::testing::Values(
+        test::UserDefinedTimestampTestMode::kStripUserDefinedTimestamp,
+        test::UserDefinedTimestampTestMode::kNormal));
+
 TEST_F(DBWALTest, RecoverWithTableHandle) {
   do {
     Options options = CurrentOptions();

db/dbformat.cc

@@ -120,6 +120,16 @@ void StripTimestampFromInternalKey(std::string* result, const Slice& key,
                  kNumInternalBytes);
 }
 
+void ReplaceInternalKeyWithMinTimestamp(std::string* result, const Slice& key,
+                                        size_t ts_sz) {
+  const size_t key_sz = key.size();
+  assert(key_sz >= ts_sz + kNumInternalBytes);
+  result->reserve(key_sz);
+  result->append(key.data(), key_sz - kNumInternalBytes - ts_sz);
+  result->append(ts_sz, static_cast<unsigned char>(0));
+  result->append(key.data() + key_sz - kNumInternalBytes, kNumInternalBytes);
+}
+
 std::string ParsedInternalKey::DebugString(bool log_err_key, bool hex) const {
   std::string result = "'";
   if (log_err_key) {

db/dbformat.h

@@ -168,51 +168,57 @@ inline void UnPackSequenceAndType(uint64_t packed, uint64_t* seq,
 EntryType GetEntryType(ValueType value_type);
 
 // Append the serialization of "key" to *result.
-extern void AppendInternalKey(std::string* result,
-                              const ParsedInternalKey& key);
+void AppendInternalKey(std::string* result, const ParsedInternalKey& key);
 
 // Append the serialization of "key" to *result, replacing the original
 // timestamp with argument ts.
-extern void AppendInternalKeyWithDifferentTimestamp(
-    std::string* result, const ParsedInternalKey& key, const Slice& ts);
+void AppendInternalKeyWithDifferentTimestamp(std::string* result,
+                                             const ParsedInternalKey& key,
+                                             const Slice& ts);
 
 // Serialized internal key consists of user key followed by footer.
 // This function appends the footer to *result, assuming that *result already
 // contains the user key at the end.
-extern void AppendInternalKeyFooter(std::string* result, SequenceNumber s,
-                                    ValueType t);
+void AppendInternalKeyFooter(std::string* result, SequenceNumber s,
+                             ValueType t);
 
 // Append the key and a minimal timestamp to *result
-extern void AppendKeyWithMinTimestamp(std::string* result, const Slice& key,
-                                      size_t ts_sz);
+void AppendKeyWithMinTimestamp(std::string* result, const Slice& key,
+                               size_t ts_sz);
 
 // Append the key and a maximal timestamp to *result
-extern void AppendKeyWithMaxTimestamp(std::string* result, const Slice& key,
-                                      size_t ts_sz);
+void AppendKeyWithMaxTimestamp(std::string* result, const Slice& key,
+                               size_t ts_sz);
 
 // `key` is a user key with timestamp. Append the user key without timestamp
 // and the maximal timestamp to *result.
-extern void AppendUserKeyWithMaxTimestamp(std::string* result, const Slice& key,
-                                          size_t ts_sz);
+void AppendUserKeyWithMaxTimestamp(std::string* result, const Slice& key,
+                                   size_t ts_sz);
 
 // `key` is an internal key containing a user key without timestamp. Create a
 // new key in *result by padding a min timestamp of size `ts_sz` to the user key
 // and copying the remaining internal key bytes.
-extern void PadInternalKeyWithMinTimestamp(std::string* result,
-                                           const Slice& key, size_t ts_sz);
+void PadInternalKeyWithMinTimestamp(std::string* result, const Slice& key,
+                                    size_t ts_sz);
 
 // `key` is an internal key containing a user key with timestamp of size
 // `ts_sz`. Create a new internal key in *result by stripping the timestamp from
 // the user key and copying the remaining internal key bytes.
-extern void StripTimestampFromInternalKey(std::string* result, const Slice& key,
-                                          size_t ts_sz);
+void StripTimestampFromInternalKey(std::string* result, const Slice& key,
+                                   size_t ts_sz);
+
+// `key` is an internal key containing a user key with timestamp of size
+// `ts_sz`. Create a new internal key in *result while replace the original
+// timestamp with min timestamp.
+void ReplaceInternalKeyWithMinTimestamp(std::string* result, const Slice& key,
+                                        size_t ts_sz);
 
 // Attempt to parse an internal key from "internal_key".  On success,
 // stores the parsed data in "*result", and returns true.
 //
 // On error, returns false, leaves "*result" in an undefined state.
-extern Status ParseInternalKey(const Slice& internal_key,
-                               ParsedInternalKey* result, bool log_err_key);
+Status ParseInternalKey(const Slice& internal_key, ParsedInternalKey* result,
+                        bool log_err_key);
 
 // Returns the user key portion of an internal key.
 inline Slice ExtractUserKey(const Slice& internal_key) {
@@ -783,8 +789,7 @@ class InternalKeySliceTransform : public SliceTransform {
 // Read the key of a record from a write batch.
 // if this record represent the default column family then cf_record
 // must be passed as false, otherwise it must be passed as true.
-extern bool ReadKeyFromWriteBatchEntry(Slice* input, Slice* key,
-                                       bool cf_record);
+bool ReadKeyFromWriteBatchEntry(Slice* input, Slice* key, bool cf_record);
 
 // Read record from a write batch piece from input.
 // tag, column_family, key, value and blob are return values. Callers own the
@@ -793,9 +798,9 @@ extern bool ReadKeyFromWriteBatchEntry(Slice* input, Slice* key,
 // input will be advanced to after the record.
 // If user-defined timestamp is enabled for a column family, then the `key`
 // resulting from this call will include timestamp.
-extern Status ReadRecordFromWriteBatch(Slice* input, char* tag,
-                                       uint32_t* column_family, Slice* key,
-                                       Slice* value, Slice* blob, Slice* xid);
+Status ReadRecordFromWriteBatch(Slice* input, char* tag,
+                                uint32_t* column_family, Slice* key,
+                                Slice* value, Slice* blob, Slice* xid);
 
 // When user call DeleteRange() to delete a range of keys,
 // we will store a serialized RangeTombstone in MemTable and SST.

db/dbformat_test.cc

@@ -312,6 +312,27 @@ TEST_F(FormatTest, StripTimestampFromInternalKey) {
   ASSERT_EQ(kTypeValue, key_without_timestamp.type);
 }
 
+TEST_F(FormatTest, ReplaceInternalKeyWithMinTimestamp) {
+  std::string orig_user_key = "foo";
+  size_t ts_sz = 8;
+  orig_user_key.append(ts_sz, static_cast<unsigned char>(1));
+  std::string orig_internal_key = IKey(orig_user_key, 100, kTypeValue);
+
+  std::string key_buf;
+  ReplaceInternalKeyWithMinTimestamp(&key_buf, orig_internal_key, ts_sz);
+  ParsedInternalKey new_key;
+  Slice in(key_buf);
+  ASSERT_OK(ParseInternalKey(in, &new_key, true /*log_err_key*/));
+
+  std::string min_timestamp(ts_sz, static_cast<unsigned char>(0));
+  size_t ukey_diff_offset = new_key.user_key.difference_offset(orig_user_key);
+  ASSERT_EQ(min_timestamp,
+            Slice(new_key.user_key.data() + ukey_diff_offset, ts_sz));
+  ASSERT_EQ(orig_user_key.size(), new_key.user_key.size());
+  ASSERT_EQ(100, new_key.sequence);
+  ASSERT_EQ(kTypeValue, new_key.type);
+}
+
 }  // namespace ROCKSDB_NAMESPACE
 
 int main(int argc, char** argv) {