Support for Merge in Integrated BlobDB with base values (#8292)

Summary:
This PR add support for Merge operation in Integrated BlobDB with base values(i.e DB::Put). Merged values can be retrieved through  DB::Get, DB::MultiGet, DB::GetMergeOperands and Iterator operation.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8292

Test Plan: Add new unit tests

Reviewed By: ltamasi

Differential Revision: D28415896

Pulled By: akankshamahajan15

fbshipit-source-id: e9b3478bef51d2f214fb88c31ed3c8d2f4a531ff

CMakeLists.txt

@@ -628,6 +628,7 @@ set(SOURCES
         cache/lru_cache.cc
         cache/sharded_cache.cc
         db/arena_wrapped_db_iter.cc
+        db/blob/blob_fetcher.cc
         db/blob/blob_file_addition.cc
         db/blob/blob_file_builder.cc
         db/blob/blob_file_cache.cc

TARGETS

@@ -137,6 +137,7 @@ cpp_library(
         "cache/lru_cache.cc",
         "cache/sharded_cache.cc",
         "db/arena_wrapped_db_iter.cc",
+        "db/blob/blob_fetcher.cc",
         "db/blob/blob_file_addition.cc",
         "db/blob/blob_file_builder.cc",
         "db/blob/blob_file_cache.cc",
@@ -448,6 +449,7 @@ cpp_library(
         "cache/lru_cache.cc",
         "cache/sharded_cache.cc",
         "db/arena_wrapped_db_iter.cc",
+        "db/blob/blob_fetcher.cc",
         "db/blob/blob_file_addition.cc",
         "db/blob/blob_file_builder.cc",
         "db/blob/blob_file_cache.cc",

db/blob/blob_fetcher.cc

@@ -0,0 +1,22 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#include "db/blob/blob_fetcher.h"
+
+#include "db/version_set.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+Status BlobFetcher::FetchBlob(const Slice& user_key, const Slice& blob_index,
+                              PinnableSlice* blob_value) {
+  Status s;
+  assert(version_);
+  constexpr uint64_t* bytes_read = nullptr;
+  s = version_->GetBlob(read_options_, user_key, blob_index, blob_value,
+                        bytes_read);
+  return s;
+}
+
+}  // namespace ROCKSDB_NAMESPACE

db/blob/blob_fetcher.h

@@ -0,0 +1,26 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include "rocksdb/options.h"
+#include "rocksdb/status.h"
+
+namespace ROCKSDB_NAMESPACE {
+class Version;
+
+class BlobFetcher {
+ public:
+  BlobFetcher(Version* version, const ReadOptions& read_options)
+      : version_(version), read_options_(read_options) {}
+
+  Status FetchBlob(const Slice& user_key, const Slice& blob_index,
+                   PinnableSlice* blob_value);
+
+ private:
+  Version* version_;
+  ReadOptions read_options_;
+};
+}  // namespace ROCKSDB_NAMESPACE

db/blob/db_blob_basic_test.cc

@@ -310,6 +310,63 @@ TEST_F(DBBlobBasicTest, BestEffortsRecovery_MissingNewestBlobFile) {
   ASSERT_EQ("value" + std::to_string(kNumTableFiles - 2), value);
 }
 
+TEST_F(DBBlobBasicTest, GetMergeBlobWithPut) {
+  Options options = GetDefaultOptions();
+  options.merge_operator = MergeOperators::CreateStringAppendOperator();
+  options.enable_blob_files = true;
+  options.min_blob_size = 0;
+
+  Reopen(options);
+
+  ASSERT_OK(Put("Key1", "v1"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(Merge("Key1", "v2"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(Merge("Key1", "v3"));
+  ASSERT_OK(Flush());
+
+  std::string value;
+  ASSERT_OK(db_->Get(ReadOptions(), "Key1", &value));
+  ASSERT_EQ(Get("Key1"), "v1,v2,v3");
+}
+
+TEST_F(DBBlobBasicTest, MultiGetMergeBlobWithPut) {
+  constexpr size_t num_keys = 3;
+
+  Options options = GetDefaultOptions();
+  options.merge_operator = MergeOperators::CreateStringAppendOperator();
+  options.enable_blob_files = true;
+  options.min_blob_size = 0;
+
+  Reopen(options);
+
+  ASSERT_OK(Put("Key0", "v0_0"));
+  ASSERT_OK(Put("Key1", "v1_0"));
+  ASSERT_OK(Put("Key2", "v2_0"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(Merge("Key0", "v0_1"));
+  ASSERT_OK(Merge("Key1", "v1_1"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(Merge("Key0", "v0_2"));
+  ASSERT_OK(Flush());
+
+  std::array<Slice, num_keys> keys{{"Key0", "Key1", "Key2"}};
+  std::array<PinnableSlice, num_keys> values;
+  std::array<Status, num_keys> statuses;
+
+  db_->MultiGet(ReadOptions(), db_->DefaultColumnFamily(), num_keys, &keys[0],
+                &values[0], &statuses[0]);
+
+  ASSERT_OK(statuses[0]);
+  ASSERT_EQ(values[0], "v0_0,v0_1,v0_2");
+
+  ASSERT_OK(statuses[1]);
+  ASSERT_EQ(values[1], "v1_0,v1_1");
+
+  ASSERT_OK(statuses[2]);
+  ASSERT_EQ(values[2], "v2_0");
+}
+
 class DBBlobBasicIOErrorTest : public DBBlobBasicTest,
                                public testing::WithParamInterface<std::string> {
  protected:

db/blob/db_blob_index_test.cc

@@ -399,7 +399,7 @@ TEST_F(DBBlobIndexTest, Iterate) {
            create_normal_iterator);
     verify(9, Status::kOk, get_value(10, 0), get_value(8, 0),
            create_normal_iterator);
-    verify(11, Status::kNotSupported, "", "", create_normal_iterator);
+    verify(11, Status::kCorruption, "", "", create_normal_iterator);
     verify(13, Status::kOk,
            get_value(13, 2) + "," + get_value(13, 1) + "," + get_value(13, 0),
            get_value(13, 2) + "," + get_value(13, 1) + "," + get_value(13, 0),
@@ -418,7 +418,11 @@ TEST_F(DBBlobIndexTest, Iterate) {
            create_blob_iterator, check_is_blob(false));
     verify(9, Status::kOk, get_value(10, 0), get_value(8, 0),
            create_blob_iterator, check_is_blob(false));
-    verify(11, Status::kNotSupported, "", "", create_blob_iterator);
+    if (tier <= kImmutableMemtables) {
+      verify(11, Status::kNotSupported, "", "", create_blob_iterator);
+    } else {
+      verify(11, Status::kCorruption, "", "", create_blob_iterator);
+    }
     verify(13, Status::kOk,
            get_value(13, 2) + "," + get_value(13, 1) + "," + get_value(13, 0),
            get_value(13, 2) + "," + get_value(13, 1) + "," + get_value(13, 0),
@@ -440,7 +444,11 @@ TEST_F(DBBlobIndexTest, Iterate) {
            create_blob_iterator, check_is_blob(false));
     verify(9, Status::kOk, get_value(10, 0), get_value(8, 0),
            create_blob_iterator, check_is_blob(false));
-    verify(11, Status::kNotSupported, "", "", create_blob_iterator);
+    if (tier <= kImmutableMemtables) {
+      verify(11, Status::kNotSupported, "", "", create_blob_iterator);
+    } else {
+      verify(11, Status::kCorruption, "", "", create_blob_iterator);
+    }
     verify(13, Status::kOk,
            get_value(13, 2) + "," + get_value(13, 1) + "," + get_value(13, 0),
            get_value(13, 2) + "," + get_value(13, 1) + "," + get_value(13, 0),
@@ -455,6 +463,106 @@ TEST_F(DBBlobIndexTest, Iterate) {
   }
 }
 
+TEST_F(DBBlobIndexTest, IntegratedBlobIterate) {
+  const std::vector<std::vector<std::string>> data = {
+      /*00*/ {"Put"},
+      /*01*/ {"Put", "Merge", "Merge", "Merge"},
+      /*02*/ {"Put"}};
+
+  auto get_key = [](size_t index) { return ("key" + std::to_string(index)); };
+
+  auto get_value = [&](size_t index, size_t version) {
+    return get_key(index) + "_value" + ToString(version);
+  };
+
+  auto check_iterator = [&](Iterator* iterator, Status expected_status,
+                            const Slice& expected_value) {
+    ASSERT_EQ(expected_status, iterator->status());
+    if (expected_status.ok()) {
+      ASSERT_TRUE(iterator->Valid());
+      ASSERT_EQ(expected_value, iterator->value());
+    } else {
+      ASSERT_FALSE(iterator->Valid());
+    }
+  };
+
+  auto verify = [&](size_t index, Status expected_status,
+                    const Slice& expected_value) {
+    // Seek
+    {
+      Iterator* iterator = db_->NewIterator(ReadOptions());
+      std::unique_ptr<Iterator> iterator_guard(iterator);
+      ASSERT_OK(iterator->status());
+      ASSERT_OK(iterator->Refresh());
+      iterator->Seek(get_key(index));
+      check_iterator(iterator, expected_status, expected_value);
+    }
+    // Next
+    {
+      Iterator* iterator = db_->NewIterator(ReadOptions());
+      std::unique_ptr<Iterator> iterator_guard(iterator);
+      ASSERT_OK(iterator->Refresh());
+      iterator->Seek(get_key(index - 1));
+      ASSERT_TRUE(iterator->Valid());
+      ASSERT_OK(iterator->status());
+      iterator->Next();
+      check_iterator(iterator, expected_status, expected_value);
+    }
+    // SeekForPrev
+    {
+      Iterator* iterator = db_->NewIterator(ReadOptions());
+      std::unique_ptr<Iterator> iterator_guard(iterator);
+      ASSERT_OK(iterator->status());
+      ASSERT_OK(iterator->Refresh());
+      iterator->SeekForPrev(get_key(index));
+      check_iterator(iterator, expected_status, expected_value);
+    }
+    // Prev
+    {
+      Iterator* iterator = db_->NewIterator(ReadOptions());
+      std::unique_ptr<Iterator> iterator_guard(iterator);
+      iterator->Seek(get_key(index + 1));
+      ASSERT_TRUE(iterator->Valid());
+      ASSERT_OK(iterator->status());
+      iterator->Prev();
+      check_iterator(iterator, expected_status, expected_value);
+    }
+  };
+
+  Options options = GetTestOptions();
+  options.enable_blob_files = true;
+  options.min_blob_size = 0;
+
+  DestroyAndReopen(options);
+
+  // fill data
+  for (size_t i = 0; i < data.size(); i++) {
+    for (size_t j = 0; j < data[i].size(); j++) {
+      std::string key = get_key(i);
+      std::string value = get_value(i, j);
+      if (data[i][j] == "Put") {
+        ASSERT_OK(Put(key, value));
+        ASSERT_OK(Flush());
+      } else if (data[i][j] == "Merge") {
+        ASSERT_OK(Merge(key, value));
+        ASSERT_OK(Flush());
+      }
+    }
+  }
+
+  std::string expected_value = get_value(1, 0) + "," + get_value(1, 1) + "," +
+                               get_value(1, 2) + "," + get_value(1, 3);
+  Status expected_status;
+  verify(1, expected_status, expected_value);
+
+#ifndef ROCKSDB_LITE
+  // Test DBIter::FindValueForCurrentKeyUsingSeek flow.
+  ASSERT_OK(dbfull()->SetOptions(cfh(),
+                                 {{"max_sequential_skip_in_iterations", "0"}}));
+  verify(1, expected_status, expected_value);
+#endif  // !ROCKSDB_LITE
+}
+
 }  // namespace ROCKSDB_NAMESPACE
 
 int main(int argc, char** argv) {

db/db_iter.cc

@@ -576,12 +576,8 @@ bool DBIter::MergeValuesNewToOld() {
       // hit a put, merge the put value with operands and store the
       // final result in saved_value_. We are done!
       const Slice val = iter_.value();
-      Status s = MergeHelper::TimedFullMerge(
-          merge_operator_, ikey.user_key, &val, merge_context_.GetOperands(),
-          &saved_value_, logger_, statistics_, clock_, &pinned_value_, true);
+      Status s = Merge(&val, ikey.user_key);
       if (!s.ok()) {
-        valid_ = false;
-        status_ = s;
         return false;
       }
       // iter_ is positioned after put
@@ -598,9 +594,31 @@ bool DBIter::MergeValuesNewToOld() {
           iter_.value(), iter_.iter()->IsValuePinned() /* operand_pinned */);
       PERF_COUNTER_ADD(internal_merge_count, 1);
     } else if (kTypeBlobIndex == ikey.type) {
-      status_ = Status::NotSupported("BlobDB does not support merge operator.");
-      valid_ = false;
-      return false;
+      if (expose_blob_index_) {
+        status_ =
+            Status::NotSupported("BlobDB does not support merge operator.");
+        valid_ = false;
+        return false;
+      }
+      // hit a put, merge the put value with operands and store the
+      // final result in saved_value_. We are done!
+      if (!SetBlobValueIfNeeded(ikey.user_key, iter_.value())) {
+        return false;
+      }
+      valid_ = true;
+      const Slice blob_value = value();
+      Status s = Merge(&blob_value, ikey.user_key);
+      if (!s.ok()) {
+        return false;
+      }
+      is_blob_ = false;
+      // iter_ is positioned after put
+      iter_.Next();
+      if (!iter_.status().ok()) {
+        valid_ = false;
+        return false;
+      }
+      return true;
     } else {
       valid_ = false;
       status_ = Status::Corruption(
@@ -619,16 +637,10 @@ bool DBIter::MergeValuesNewToOld() {
   // a deletion marker.
   // feed null as the existing value to the merge operator, such that
   // client can differentiate this scenario and do things accordingly.
-  Status s = MergeHelper::TimedFullMerge(
-      merge_operator_, saved_key_.GetUserKey(), nullptr,
-      merge_context_.GetOperands(), &saved_value_, logger_, statistics_, clock_,
-      &pinned_value_, true);
+  Status s = Merge(nullptr, saved_key_.GetUserKey());
   if (!s.ok()) {
-    valid_ = false;
-    status_ = s;
     return false;
   }
-
   assert(status_.ok());
   return true;
 }
@@ -931,21 +943,36 @@ bool DBIter::FindValueForCurrentKey() {
       if (last_not_merge_type == kTypeDeletion ||
           last_not_merge_type == kTypeSingleDeletion ||
           last_not_merge_type == kTypeRangeDeletion) {
-        s = MergeHelper::TimedFullMerge(
-            merge_operator_, saved_key_.GetUserKey(), nullptr,
-            merge_context_.GetOperands(), &saved_value_, logger_, statistics_,
-            clock_, &pinned_value_, true);
+        s = Merge(nullptr, saved_key_.GetUserKey());
+        if (!s.ok()) {
+          return false;
+        }
+        return true;
       } else if (last_not_merge_type == kTypeBlobIndex) {
-        status_ =
-            Status::NotSupported("BlobDB does not support merge operator.");
-        valid_ = false;
-        return false;
+        if (expose_blob_index_) {
+          status_ =
+              Status::NotSupported("BlobDB does not support merge operator.");
+          valid_ = false;
+          return false;
+        }
+        if (!SetBlobValueIfNeeded(saved_key_.GetUserKey(), pinned_value_)) {
+          return false;
+        }
+        valid_ = true;
+        const Slice blob_value = value();
+        s = Merge(&blob_value, saved_key_.GetUserKey());
+        if (!s.ok()) {
+          return false;
+        }
+        is_blob_ = false;
+        return true;
       } else {
         assert(last_not_merge_type == kTypeValue);
-        s = MergeHelper::TimedFullMerge(
-            merge_operator_, saved_key_.GetUserKey(), &pinned_value_,
-            merge_context_.GetOperands(), &saved_value_, logger_, statistics_,
-            clock_, &pinned_value_, true);
+        s = Merge(&pinned_value_, saved_key_.GetUserKey());
+        if (!s.ok()) {
+          return false;
+        }
+        return true;
       }
       break;
     case kTypeValue:
@@ -955,7 +982,6 @@ bool DBIter::FindValueForCurrentKey() {
       if (!SetBlobValueIfNeeded(saved_key_.GetUserKey(), pinned_value_)) {
         return false;
       }
-
       break;
     default:
       valid_ = false;
@@ -1095,25 +1121,33 @@ bool DBIter::FindValueForCurrentKeyUsingSeek() {
 
     if (ikey.type == kTypeValue) {
       const Slice val = iter_.value();
-      Status s = MergeHelper::TimedFullMerge(
-          merge_operator_, saved_key_.GetUserKey(), &val,
-          merge_context_.GetOperands(), &saved_value_, logger_, statistics_,
-          clock_, &pinned_value_, true);
+      Status s = Merge(&val, saved_key_.GetUserKey());
       if (!s.ok()) {
-        valid_ = false;
-        status_ = s;
         return false;
       }
-      valid_ = true;
       return true;
     } else if (ikey.type == kTypeMerge) {
       merge_context_.PushOperand(
           iter_.value(), iter_.iter()->IsValuePinned() /* operand_pinned */);
       PERF_COUNTER_ADD(internal_merge_count, 1);
     } else if (ikey.type == kTypeBlobIndex) {
-      status_ = Status::NotSupported("BlobDB does not support merge operator.");
-      valid_ = false;
-      return false;
+      if (expose_blob_index_) {
+        status_ =
+            Status::NotSupported("BlobDB does not support merge operator.");
+        valid_ = false;
+        return false;
+      }
+      if (!SetBlobValueIfNeeded(ikey.user_key, iter_.value())) {
+        return false;
+      }
+      valid_ = true;
+      const Slice blob_value = value();
+      Status s = Merge(&blob_value, saved_key_.GetUserKey());
+      if (!s.ok()) {
+        return false;
+      }
+      is_blob_ = false;
+      return true;
     } else {
       valid_ = false;
       status_ = Status::Corruption(
@@ -1123,13 +1157,8 @@ bool DBIter::FindValueForCurrentKeyUsingSeek() {
     }
   }
 
-  Status s = MergeHelper::TimedFullMerge(
-      merge_operator_, saved_key_.GetUserKey(), nullptr,
-      merge_context_.GetOperands(), &saved_value_, logger_, statistics_, clock_,
-      &pinned_value_, true);
+  Status s = Merge(nullptr, saved_key_.GetUserKey());
   if (!s.ok()) {
-    valid_ = false;
-    status_ = s;
     return false;
   }
 
@@ -1152,6 +1181,19 @@ bool DBIter::FindValueForCurrentKeyUsingSeek() {
   return true;
 }
 
+Status DBIter::Merge(const Slice* val, const Slice& user_key) {
+  Status s = MergeHelper::TimedFullMerge(
+      merge_operator_, user_key, val, merge_context_.GetOperands(),
+      &saved_value_, logger_, statistics_, clock_, &pinned_value_, true);
+  if (!s.ok()) {
+    valid_ = false;
+    status_ = s;
+    return s;
+  }
+  valid_ = true;
+  return s;
+}
+
 // Move backwards until the key smaller than saved_key_.
 // Changes valid_ only if return value is false.
 bool DBIter::FindUserKeyBeforeSavedKey() {

db/db_iter.h

@@ -299,6 +299,8 @@ class DBIter final : public Iterator {
   // index when using the integrated BlobDB implementation.
   bool SetBlobValueIfNeeded(const Slice& user_key, const Slice& blob_index);
 
+  Status Merge(const Slice* val, const Slice& user_key);
+
   const SliceTransform* prefix_extractor_;
   Env* const env_;
   SystemClock* clock_;

db/db_merge_operand_test.cc

@@ -19,33 +19,35 @@
 
 namespace ROCKSDB_NAMESPACE {
 
-class DBMergeOperandTest : public DBTestBase {
+namespace {
+class LimitedStringAppendMergeOp : public StringAppendTESTOperator {
  public:
-  DBMergeOperandTest()
-      : DBTestBase("/db_merge_operand_test", /*env_do_fsync=*/true) {}
-};
+  LimitedStringAppendMergeOp(int limit, char delim)
+      : StringAppendTESTOperator(delim), limit_(limit) {}
 
-TEST_F(DBMergeOperandTest, GetMergeOperandsBasic) {
-  class LimitedStringAppendMergeOp : public StringAppendTESTOperator {
-   public:
-    LimitedStringAppendMergeOp(int limit, char delim)
-        : StringAppendTESTOperator(delim), limit_(limit) {}
+  const char* Name() const override {
+    return "DBMergeOperatorTest::LimitedStringAppendMergeOp";
+  }
 
-    const char* Name() const override {
-      return "DBMergeOperatorTest::LimitedStringAppendMergeOp";
+  bool ShouldMerge(const std::vector<Slice>& operands) const override {
+    if (operands.size() > 0 && limit_ > 0 && operands.size() >= limit_) {
+      return true;
     }
+    return false;
+  }
 
-    bool ShouldMerge(const std::vector<Slice>& operands) const override {
-      if (operands.size() > 0 && limit_ > 0 && operands.size() >= limit_) {
-        return true;
-      }
-      return false;
-    }
+ private:
+  size_t limit_ = 0;
+};
+}  // namespace
 
-   private:
-    size_t limit_ = 0;
-  };
+class DBMergeOperandTest : public DBTestBase {
+ public:
+  DBMergeOperandTest()
+      : DBTestBase("/db_merge_operand_test", /*env_do_fsync=*/true) {}
+};
 
+TEST_F(DBMergeOperandTest, GetMergeOperandsBasic) {
   Options options;
   options.create_if_missing = true;
   // Use only the latest two merge operands.
@@ -214,7 +216,8 @@ TEST_F(DBMergeOperandTest, GetMergeOperandsBasic) {
   ASSERT_EQ(values[2], "dc");
   ASSERT_EQ(values[3], "ed");
 
-  // First 3 k5 values are in SST and next 4 k5 values are in Immutable Memtable
+  // First 3 k5 values are in SST and next 4 k5 values are in Immutable
+  // Memtable
   ASSERT_OK(Merge("k5", "who"));
   ASSERT_OK(Merge("k5", "am"));
   ASSERT_OK(Merge("k5", "i"));
@@ -232,6 +235,93 @@ TEST_F(DBMergeOperandTest, GetMergeOperandsBasic) {
   ASSERT_EQ(values[2], "am");
 }
 
+TEST_F(DBMergeOperandTest, BlobDBGetMergeOperandsBasic) {
+  Options options;
+  options.create_if_missing = true;
+  options.enable_blob_files = true;
+  options.min_blob_size = 0;
+  // Use only the latest two merge operands.
+  options.merge_operator = std::make_shared<LimitedStringAppendMergeOp>(2, ',');
+  options.env = env_;
+  Reopen(options);
+  int num_records = 4;
+  int number_of_operands = 0;
+  std::vector<PinnableSlice> values(num_records);
+  GetMergeOperandsOptions merge_operands_info;
+  merge_operands_info.expected_max_number_of_operands = num_records;
+
+  // All k1 values are in memtable.
+  ASSERT_OK(Put("k1", "x"));
+  ASSERT_OK(Merge("k1", "b"));
+  ASSERT_OK(Merge("k1", "c"));
+  ASSERT_OK(Merge("k1", "d"));
+  ASSERT_OK(db_->GetMergeOperands(ReadOptions(), db_->DefaultColumnFamily(),
+                                  "k1", values.data(), &merge_operands_info,
+                                  &number_of_operands));
+  ASSERT_EQ(values[0], "x");
+  ASSERT_EQ(values[1], "b");
+  ASSERT_EQ(values[2], "c");
+  ASSERT_EQ(values[3], "d");
+
+  // expected_max_number_of_operands is less than number of merge operands so
+  // status should be Incomplete.
+  merge_operands_info.expected_max_number_of_operands = num_records - 1;
+  Status status = db_->GetMergeOperands(
+      ReadOptions(), db_->DefaultColumnFamily(), "k1", values.data(),
+      &merge_operands_info, &number_of_operands);
+  ASSERT_EQ(status.IsIncomplete(), true);
+  merge_operands_info.expected_max_number_of_operands = num_records;
+
+  // All k2 values are flushed to L0 into a single file.
+  ASSERT_OK(Put("k2", "q"));
+  ASSERT_OK(Merge("k2", "w"));
+  ASSERT_OK(Merge("k2", "e"));
+  ASSERT_OK(Merge("k2", "r"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(db_->GetMergeOperands(ReadOptions(), db_->DefaultColumnFamily(),
+                                  "k2", values.data(), &merge_operands_info,
+                                  &number_of_operands));
+  ASSERT_EQ(values[0], "q,w,e,r");
+
+  // Do some compaction that will make the following tests more predictable
+  ASSERT_OK(db_->CompactRange(CompactRangeOptions(), nullptr, nullptr));
+
+  // All k3 values are flushed and are in different files.
+  ASSERT_OK(Put("k3", "ab"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(Merge("k3", "bc"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(Merge("k3", "cd"));
+  ASSERT_OK(Flush());
+  ASSERT_OK(Merge("k3", "de"));
+  ASSERT_OK(db_->GetMergeOperands(ReadOptions(), db_->DefaultColumnFamily(),
+                                  "k3", values.data(), &merge_operands_info,
+                                  &number_of_operands));
+  ASSERT_EQ(values[0], "ab");
+  ASSERT_EQ(values[1], "bc");
+  ASSERT_EQ(values[2], "cd");
+  ASSERT_EQ(values[3], "de");
+
+  // All K4 values are in different levels
+  ASSERT_OK(Put("k4", "ba"));
+  ASSERT_OK(Flush());
+  MoveFilesToLevel(4);
+  ASSERT_OK(Merge("k4", "cb"));
+  ASSERT_OK(Flush());
+  MoveFilesToLevel(3);
+  ASSERT_OK(Merge("k4", "dc"));
+  ASSERT_OK(Flush());
+  MoveFilesToLevel(1);
+  ASSERT_OK(Merge("k4", "ed"));
+  ASSERT_OK(db_->GetMergeOperands(ReadOptions(), db_->DefaultColumnFamily(),
+                                  "k4", values.data(), &merge_operands_info,
+                                  &number_of_operands));
+  ASSERT_EQ(values[0], "ba");
+  ASSERT_EQ(values[1], "cb");
+  ASSERT_EQ(values[2], "dc");
+  ASSERT_EQ(values[3], "ed");
+}
+
 }  // namespace ROCKSDB_NAMESPACE
 
 int main(int argc, char** argv) {

db/version_set.cc

@@ -21,6 +21,7 @@
 #include <vector>
 
 #include "compaction/compaction.h"
+#include "db/blob/blob_fetcher.h"
 #include "db/blob/blob_file_cache.h"
 #include "db/blob/blob_file_reader.h"
 #include "db/blob/blob_index.h"
@@ -1875,6 +1876,7 @@ void Version::Get(const ReadOptions& read_options, const LookupKey& k,
   // need to provide it here.
   bool is_blob_index = false;
   bool* const is_blob_to_use = is_blob ? is_blob : &is_blob_index;
+  BlobFetcher blob_fetcher(this, read_options);
 
   GetContext get_context(
       user_comparator(), merge_operator_, info_log_, db_statistics_,
@@ -1882,7 +1884,7 @@ void Version::Get(const ReadOptions& read_options, const LookupKey& k,
       do_merge ? value : nullptr, do_merge ? timestamp : nullptr, value_found,
       merge_context, do_merge, max_covering_tombstone_seq, clock_, seq,
       merge_operator_ ? &pinned_iters_mgr : nullptr, callback, is_blob_to_use,
-      tracing_get_id);
+      tracing_get_id, &blob_fetcher);
 
   // Pin blocks that we read to hold merge operands
   if (merge_operator_) {
@@ -2031,6 +2033,7 @@ void Version::MultiGet(const ReadOptions& read_options, MultiGetRange* range,
   // use autovector in order to avoid unnecessary construction of GetContext
   // objects, which is expensive
   autovector<GetContext, 16> get_ctx;
+  BlobFetcher blob_fetcher(this, read_options);
   for (auto iter = range->begin(); iter != range->end(); ++iter) {
     assert(iter->s->ok() || iter->s->IsMergeInProgress());
     get_ctx.emplace_back(
@@ -2039,7 +2042,7 @@ void Version::MultiGet(const ReadOptions& read_options, MultiGetRange* range,
         iter->ukey_with_ts, iter->value, iter->timestamp, nullptr,
         &(iter->merge_context), true, &iter->max_covering_tombstone_seq, clock_,
         nullptr, merge_operator_ ? &pinned_iters_mgr : nullptr, callback,
-        &iter->is_blob_index, tracing_mget_id);
+        &iter->is_blob_index, tracing_mget_id, &blob_fetcher);
     // MergeInProgress status, if set, has been transferred to the get_context
     // state, so we set status to ok here. From now on, the iter status will
     // be used for IO errors, and get_context state will be used for any

src.mk

@@ -6,6 +6,7 @@ LIB_SOURCES =                                                   \
   cache/lru_cache.cc                                            \
   cache/sharded_cache.cc                                        \
   db/arena_wrapped_db_iter.cc                                   \
+  db/blob/blob_fetcher.cc                                       \
   db/blob/blob_file_addition.cc                                 \
   db/blob/blob_file_builder.cc                                  \
   db/blob/blob_file_cache.cc                                    \

table/get_context.cc

@@ -39,14 +39,17 @@ void appendToReplayLog(std::string* replay_log, ValueType type, Slice value) {
 
 }  // namespace
 
-GetContext::GetContext(
-    const Comparator* ucmp, const MergeOperator* merge_operator, Logger* logger,
-    Statistics* statistics, GetState init_state, const Slice& user_key,
-    PinnableSlice* pinnable_val, std::string* timestamp, bool* value_found,
-    MergeContext* merge_context, bool do_merge,
-    SequenceNumber* _max_covering_tombstone_seq, SystemClock* clock,
-    SequenceNumber* seq, PinnedIteratorsManager* _pinned_iters_mgr,
-    ReadCallback* callback, bool* is_blob_index, uint64_t tracing_get_id)
+GetContext::GetContext(const Comparator* ucmp,
+                       const MergeOperator* merge_operator, Logger* logger,
+                       Statistics* statistics, GetState init_state,
+                       const Slice& user_key, PinnableSlice* pinnable_val,
+                       std::string* timestamp, bool* value_found,
+                       MergeContext* merge_context, bool do_merge,
+                       SequenceNumber* _max_covering_tombstone_seq,
+                       SystemClock* clock, SequenceNumber* seq,
+                       PinnedIteratorsManager* _pinned_iters_mgr,
+                       ReadCallback* callback, bool* is_blob_index,
+                       uint64_t tracing_get_id, BlobFetcher* blob_fetcher)
     : ucmp_(ucmp),
       merge_operator_(merge_operator),
       logger_(logger),
@@ -65,7 +68,8 @@ GetContext::GetContext(
       callback_(callback),
       do_merge_(do_merge),
       is_blob_index_(is_blob_index),
-      tracing_get_id_(tracing_get_id) {
+      tracing_get_id_(tracing_get_id),
+      blob_fetcher_(blob_fetcher) {
   if (seq_) {
     *seq_ = kMaxSequenceNumber;
   }
@@ -79,11 +83,11 @@ GetContext::GetContext(
     bool do_merge, SequenceNumber* _max_covering_tombstone_seq,
     SystemClock* clock, SequenceNumber* seq,
     PinnedIteratorsManager* _pinned_iters_mgr, ReadCallback* callback,
-    bool* is_blob_index, uint64_t tracing_get_id)
+    bool* is_blob_index, uint64_t tracing_get_id, BlobFetcher* blob_fetcher)
     : GetContext(ucmp, merge_operator, logger, statistics, init_state, user_key,
                  pinnable_val, nullptr, value_found, merge_context, do_merge,
                  _max_covering_tombstone_seq, clock, seq, _pinned_iters_mgr,
-                 callback, is_blob_index, tracing_get_id) {}
+                 callback, is_blob_index, tracing_get_id, blob_fetcher) {}
 
 // Called from TableCache::Get and Table::Get when file/block in which
 // key may exist are not there in TableCache/BlockCache respectively. In this
@@ -250,6 +254,9 @@ bool GetContext::SaveValue(const ParsedInternalKey& parsed_key,
           state_ = kUnexpectedBlobIndex;
           return false;
         }
+        if (is_blob_index_ != nullptr) {
+          *is_blob_index_ = (type == kTypeBlobIndex);
+        }
         if (kNotFound == state_) {
           state_ = kFound;
           if (do_merge_) {
@@ -260,7 +267,6 @@ bool GetContext::SaveValue(const ParsedInternalKey& parsed_key,
               } else {
                 TEST_SYNC_POINT_CALLBACK("GetContext::SaveValue::PinSelf",
                                          this);
-
                 // Otherwise copy the value
                 pinnable_val_->PinSelf(value);
               }
@@ -269,27 +275,44 @@ bool GetContext::SaveValue(const ParsedInternalKey& parsed_key,
             // It means this function is called as part of DB GetMergeOperands
             // API and the current value should be part of
             // merge_context_->operand_list
-            push_operand(value, value_pinner);
+            if (is_blob_index_ != nullptr && *is_blob_index_) {
+              PinnableSlice pin_val;
+              if (GetBlobValue(value, &pin_val) == false) {
+                return false;
+              }
+              Slice blob_value(pin_val);
+              push_operand(blob_value, nullptr);
+            } else {
+              push_operand(value, value_pinner);
+            }
           }
         } else if (kMerge == state_) {
           assert(merge_operator_ != nullptr);
-          state_ = kFound;
-          if (do_merge_) {
-            if (LIKELY(pinnable_val_ != nullptr)) {
-              Status merge_status = MergeHelper::TimedFullMerge(
-                  merge_operator_, user_key_, &value,
-                  merge_context_->GetOperands(), pinnable_val_->GetSelf(),
-                  logger_, statistics_, clock_);
-              pinnable_val_->PinSelf();
-              if (!merge_status.ok()) {
-                state_ = kCorrupt;
-              }
+          if (is_blob_index_ != nullptr && *is_blob_index_) {
+            PinnableSlice pin_val;
+            if (GetBlobValue(value, &pin_val) == false) {
+              return false;
+            }
+            Slice blob_value(pin_val);
+            state_ = kFound;
+            if (do_merge_) {
+              Merge(&blob_value);
+            } else {
+              // It means this function is called as part of DB GetMergeOperands
+              // API and the current value should be part of
+              // merge_context_->operand_list
+              push_operand(blob_value, nullptr);
             }
           } else {
-            // It means this function is called as part of DB GetMergeOperands
-            // API and the current value should be part of
-            // merge_context_->operand_list
-            push_operand(value, value_pinner);
+            state_ = kFound;
+            if (do_merge_) {
+              Merge(&value);
+            } else {
+              // It means this function is called as part of DB GetMergeOperands
+              // API and the current value should be part of
+              // merge_context_->operand_list
+              push_operand(value, value_pinner);
+            }
           }
         }
         if (state_ == kFound) {
@@ -299,9 +322,6 @@ bool GetContext::SaveValue(const ParsedInternalKey& parsed_key,
             timestamp_->assign(ts.data(), ts.size());
           }
         }
-        if (is_blob_index_ != nullptr) {
-          *is_blob_index_ = (type == kTypeBlobIndex);
-        }
         return false;
 
       case kTypeDeletion:
@@ -315,20 +335,9 @@ bool GetContext::SaveValue(const ParsedInternalKey& parsed_key,
           state_ = kDeleted;
         } else if (kMerge == state_) {
           state_ = kFound;
-          if (LIKELY(pinnable_val_ != nullptr)) {
-            if (do_merge_) {
-              Status merge_status = MergeHelper::TimedFullMerge(
-                  merge_operator_, user_key_, nullptr,
-                  merge_context_->GetOperands(), pinnable_val_->GetSelf(),
-                  logger_, statistics_, clock_);
-              pinnable_val_->PinSelf();
-              if (!merge_status.ok()) {
-                state_ = kCorrupt;
-              }
-            }
-            // If do_merge_ = false then the current value shouldn't be part of
-            // merge_context_->operand_list
-          }
+          Merge(nullptr);
+          // If do_merge_ = false then the current value shouldn't be part of
+          // merge_context_->operand_list
         }
         return false;
 
@@ -341,20 +350,7 @@ bool GetContext::SaveValue(const ParsedInternalKey& parsed_key,
             merge_operator_->ShouldMerge(
                 merge_context_->GetOperandsDirectionBackward())) {
           state_ = kFound;
-          if (LIKELY(pinnable_val_ != nullptr)) {
-            // do_merge_ = true this is the case where this function is called
-            // as part of DB Get API hence merge operators should be merged.
-            if (do_merge_) {
-              Status merge_status = MergeHelper::TimedFullMerge(
-                  merge_operator_, user_key_, nullptr,
-                  merge_context_->GetOperands(), pinnable_val_->GetSelf(),
-                  logger_, statistics_, clock_);
-              pinnable_val_->PinSelf();
-              if (!merge_status.ok()) {
-                state_ = kCorrupt;
-              }
-            }
-          }
+          Merge(nullptr);
           return false;
         }
         return true;
@@ -369,6 +365,35 @@ bool GetContext::SaveValue(const ParsedInternalKey& parsed_key,
   return false;
 }
 
+void GetContext::Merge(const Slice* value) {
+  if (LIKELY(pinnable_val_ != nullptr)) {
+    if (do_merge_) {
+      Status merge_status = MergeHelper::TimedFullMerge(
+          merge_operator_, user_key_, value, merge_context_->GetOperands(),
+          pinnable_val_->GetSelf(), logger_, statistics_, clock_);
+      pinnable_val_->PinSelf();
+      if (!merge_status.ok()) {
+        state_ = kCorrupt;
+      }
+    }
+  }
+}
+
+bool GetContext::GetBlobValue(const Slice& blob_index,
+                              PinnableSlice* blob_value) {
+  Status status = blob_fetcher_->FetchBlob(user_key_, blob_index, blob_value);
+  if (!status.ok()) {
+    if (status.IsIncomplete()) {
+      MarkKeyMayExist();
+      return false;
+    }
+    state_ = kCorrupt;
+    return false;
+  }
+  *is_blob_index_ = false;
+  return true;
+}
+
 void GetContext::push_operand(const Slice& value, Cleanable* value_pinner) {
   if (pinned_iters_mgr() && pinned_iters_mgr()->PinningEnabled() &&
       value_pinner != nullptr) {

table/get_context.h

@@ -5,6 +5,8 @@
 
 #pragma once
 #include <string>
+
+#include "db/blob/blob_fetcher.h"
 #include "db/dbformat.h"
 #include "db/merge_context.h"
 #include "db/read_callback.h"
@@ -103,7 +105,7 @@ class GetContext {
              SequenceNumber* seq = nullptr,
              PinnedIteratorsManager* _pinned_iters_mgr = nullptr,
              ReadCallback* callback = nullptr, bool* is_blob_index = nullptr,
-             uint64_t tracing_get_id = 0);
+             uint64_t tracing_get_id = 0, BlobFetcher* blob_fetcher = nullptr);
   GetContext(const Comparator* ucmp, const MergeOperator* merge_operator,
              Logger* logger, Statistics* statistics, GetState init_state,
              const Slice& user_key, PinnableSlice* value,
@@ -113,7 +115,7 @@ class GetContext {
              SequenceNumber* seq = nullptr,
              PinnedIteratorsManager* _pinned_iters_mgr = nullptr,
              ReadCallback* callback = nullptr, bool* is_blob_index = nullptr,
-             uint64_t tracing_get_id = 0);
+             uint64_t tracing_get_id = 0, BlobFetcher* blob_fetcher = nullptr);
 
   GetContext() = delete;
 
@@ -170,6 +172,9 @@ class GetContext {
   void push_operand(const Slice& value, Cleanable* value_pinner);
 
  private:
+  void Merge(const Slice* value);
+  bool GetBlobValue(const Slice& blob_index, PinnableSlice* blob_value);
+
   const Comparator* ucmp_;
   const MergeOperator* merge_operator_;
   // the merge operations encountered;
@@ -200,6 +205,7 @@ class GetContext {
   // Used for block cache tracing only. A tracing get id uniquely identifies a
   // Get or a MultiGet.
   const uint64_t tracing_get_id_;
+  BlobFetcher* blob_fetcher_;
 };
 
 // Call this to replay a log and bring the get_context up to date. The replay