Enable blob caching for MultiGetBlob in RocksDB (#10272)

Summary:
- [x] Enabled blob caching for MultiGetBlob in RocksDB
- [x] Refactored MultiGetBlob logic and interface in RocksDB
- [x] Cleaned up Version::MultiGetBlob() and moved 'blob'-related code snippets into BlobSource
- [x] Add End-to-end test cases in db_blob_basic_test and also add unit tests in blob_source_test

This task is a part of https://github.com/facebook/rocksdb/issues/10156

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10272

Reviewed By: ltamasi

Differential Revision: D37558112

Pulled By: gangliao

fbshipit-source-id: a73a6a94ffdee0024d5b2a39e6d1c1a7d38664db

db/blob/blob_file_reader.cc

@@ -16,6 +16,7 @@
 #include "rocksdb/file_system.h"
 #include "rocksdb/slice.h"
 #include "rocksdb/status.h"
+#include "table/multiget_context.h"
 #include "test_util/sync_point.h"
 #include "util/compression.h"
 #include "util/crc32c.h"
@@ -374,40 +375,50 @@ Status BlobFileReader::GetBlob(const ReadOptions& read_options,
   return Status::OK();
 }
 
-void BlobFileReader::MultiGetBlob(
-    const ReadOptions& read_options,
-    const autovector<std::reference_wrapper<const Slice>>& user_keys,
-    const autovector<uint64_t>& offsets,
-    const autovector<uint64_t>& value_sizes, autovector<Status*>& statuses,
-    autovector<PinnableSlice*>& values, uint64_t* bytes_read) const {
-  const size_t num_blobs = user_keys.size();
+void BlobFileReader::MultiGetBlob(const ReadOptions& read_options,
+                                  autovector<BlobReadRequest*>& blob_reqs,
+                                  uint64_t* bytes_read) const {
+  const size_t num_blobs = blob_reqs.size();
   assert(num_blobs > 0);
-  assert(num_blobs == offsets.size());
-  assert(num_blobs == value_sizes.size());
-  assert(num_blobs == statuses.size());
-  assert(num_blobs == values.size());
+  assert(num_blobs <= MultiGetContext::MAX_BATCH_SIZE);
 
 #ifndef NDEBUG
-  for (size_t i = 0; i < offsets.size() - 1; ++i) {
-    assert(offsets[i] <= offsets[i + 1]);
+  for (size_t i = 0; i < num_blobs - 1; ++i) {
+    assert(blob_reqs[i]->offset <= blob_reqs[i + 1]->offset);
   }
 #endif  // !NDEBUG
 
-  std::vector<FSReadRequest> read_reqs(num_blobs);
+  std::vector<FSReadRequest> read_reqs;
   autovector<uint64_t> adjustments;
   uint64_t total_len = 0;
+  read_reqs.reserve(num_blobs);
   for (size_t i = 0; i < num_blobs; ++i) {
-    const size_t key_size = user_keys[i].get().size();
-    assert(IsValidBlobOffset(offsets[i], key_size, value_sizes[i], file_size_));
+    const size_t key_size = blob_reqs[i]->user_key->size();
+    const uint64_t offset = blob_reqs[i]->offset;
+    const uint64_t value_size = blob_reqs[i]->len;
+
+    if (!IsValidBlobOffset(offset, key_size, value_size, file_size_)) {
+      *blob_reqs[i]->status = Status::Corruption("Invalid blob offset");
+      continue;
+    }
+    if (blob_reqs[i]->compression != compression_type_) {
+      *blob_reqs[i]->status =
+          Status::Corruption("Compression type mismatch when reading a blob");
+      continue;
+    }
+
     const uint64_t adjustment =
         read_options.verify_checksums
             ? BlobLogRecord::CalculateAdjustmentForRecordHeader(key_size)
             : 0;
-    assert(offsets[i] >= adjustment);
+    assert(blob_reqs[i]->offset >= adjustment);
     adjustments.push_back(adjustment);
-    read_reqs[i].offset = offsets[i] - adjustment;
-    read_reqs[i].len = value_sizes[i] + adjustment;
-    total_len += read_reqs[i].len;
+
+    FSReadRequest read_req;
+    read_req.offset = blob_reqs[i]->offset - adjustment;
+    read_req.len = blob_reqs[i]->len + adjustment;
+    read_reqs.emplace_back(read_req);
+    total_len += read_req.len;
   }
 
   RecordTick(statistics_, BLOB_DB_BLOB_FILE_BYTES_READ, total_len);
@@ -439,9 +450,12 @@ void BlobFileReader::MultiGetBlob(
     for (auto& req : read_reqs) {
       req.status.PermitUncheckedError();
     }
-    for (size_t i = 0; i < num_blobs; ++i) {
-      assert(statuses[i]);
-      *statuses[i] = s;
+    for (auto& req : blob_reqs) {
+      assert(req->status);
+      if (!req->status->IsCorruption()) {
+        // Avoid overwriting corruption status.
+        *req->status = s;
+      }
     }
     return;
   }
@@ -449,33 +463,39 @@ void BlobFileReader::MultiGetBlob(
   assert(s.ok());
 
   uint64_t total_bytes = 0;
-  for (size_t i = 0; i < num_blobs; ++i) {
-    auto& req = read_reqs[i];
-    const auto& record_slice = req.result;
+  for (size_t i = 0, j = 0; i < num_blobs; ++i) {
+    assert(blob_reqs[i]->status);
+    if (!blob_reqs[i]->status->ok()) {
+      continue;
+    }
 
-    assert(statuses[i]);
+    assert(j < read_reqs.size());
+    auto& req = read_reqs[j++];
+    const auto& record_slice = req.result;
     if (req.status.ok() && record_slice.size() != req.len) {
       req.status = IOStatus::Corruption("Failed to read data from blob file");
     }
 
-    *statuses[i] = req.status;
-    if (!statuses[i]->ok()) {
+    *blob_reqs[i]->status = req.status;
+    if (!blob_reqs[i]->status->ok()) {
       continue;
     }
 
     // Verify checksums if enabled
     if (read_options.verify_checksums) {
-      *statuses[i] = VerifyBlob(record_slice, user_keys[i], value_sizes[i]);
-      if (!statuses[i]->ok()) {
+      *blob_reqs[i]->status =
+          VerifyBlob(record_slice, *blob_reqs[i]->user_key, blob_reqs[i]->len);
+      if (!blob_reqs[i]->status->ok()) {
         continue;
       }
     }
 
     // Uncompress blob if needed
-    Slice value_slice(record_slice.data() + adjustments[i], value_sizes[i]);
-    *statuses[i] = UncompressBlobIfNeeded(value_slice, compression_type_,
-                                          clock_, statistics_, values[i]);
-    if (statuses[i]->ok()) {
+    Slice value_slice(record_slice.data() + adjustments[i], blob_reqs[i]->len);
+    *blob_reqs[i]->status =
+        UncompressBlobIfNeeded(value_slice, compression_type_, clock_,
+                               statistics_, blob_reqs[i]->result);
+    if (blob_reqs[i]->status->ok()) {
       total_bytes += record_slice.size();
     }
   }

db/blob/blob_file_reader.h

@@ -8,6 +8,7 @@
 #include <cinttypes>
 #include <memory>
 
+#include "db/blob/blob_read_request.h"
 #include "file/random_access_file_reader.h"
 #include "rocksdb/compression_type.h"
 #include "rocksdb/rocksdb_namespace.h"
@@ -47,12 +48,9 @@ class BlobFileReader {
                  uint64_t* bytes_read) const;
 
   // offsets must be sorted in ascending order by caller.
-  void MultiGetBlob(
-      const ReadOptions& read_options,
-      const autovector<std::reference_wrapper<const Slice>>& user_keys,
-      const autovector<uint64_t>& offsets,
-      const autovector<uint64_t>& value_sizes, autovector<Status*>& statuses,
-      autovector<PinnableSlice*>& values, uint64_t* bytes_read) const;
+  void MultiGetBlob(const ReadOptions& read_options,
+                    autovector<BlobReadRequest*>& blob_reqs,
+                    uint64_t* bytes_read) const;
 
   CompressionType GetCompressionType() const { return compression_type_; }
 

db/blob/blob_file_reader_test.cc

@@ -194,21 +194,21 @@ TEST_F(BlobFileReaderTest, CreateReaderAndGetBlob) {
     // MultiGetBlob
     bytes_read = 0;
     size_t total_size = 0;
-    autovector<std::reference_wrapper<const Slice>> key_refs;
-    for (const auto& key_ref : keys) {
-      key_refs.emplace_back(std::cref(key_ref));
-    }
-    autovector<uint64_t> offsets{blob_offsets[0], blob_offsets[1],
-                                 blob_offsets[2]};
-    autovector<uint64_t> sizes{blob_sizes[0], blob_sizes[1], blob_sizes[2]};
+
     std::array<Status, num_blobs> statuses_buf;
-    autovector<Status*> statuses{&statuses_buf[0], &statuses_buf[1],
-                                 &statuses_buf[2]};
     std::array<PinnableSlice, num_blobs> value_buf;
-    autovector<PinnableSlice*> values{&value_buf[0], &value_buf[1],
-                                      &value_buf[2]};
-    reader->MultiGetBlob(read_options, key_refs, offsets, sizes, statuses,
-                         values, &bytes_read);
+    std::array<BlobReadRequest, num_blobs> requests_buf;
+    autovector<BlobReadRequest*> blob_reqs;
+
+    for (size_t i = 0; i < num_blobs; ++i) {
+      requests_buf[i] =
+          BlobReadRequest(keys[i], blob_offsets[i], blob_sizes[i],
+                          kNoCompression, &value_buf[i], &statuses_buf[i]);
+      blob_reqs.push_back(&requests_buf[i]);
+    }
+
+    reader->MultiGetBlob(read_options, blob_reqs, &bytes_read);
+
     for (size_t i = 0; i < num_blobs; ++i) {
       ASSERT_OK(statuses_buf[i]);
       ASSERT_EQ(value_buf[i], blobs[i]);
@@ -300,15 +300,21 @@ TEST_F(BlobFileReaderTest, CreateReaderAndGetBlob) {
         blob_offsets[0],
         blob_offsets[1] - (keys[1].size() - key_refs[1].get().size()),
         blob_offsets[2]};
-    autovector<uint64_t> sizes{blob_sizes[0], blob_sizes[1], blob_sizes[2]};
+
     std::array<Status, num_blobs> statuses_buf;
-    autovector<Status*> statuses{&statuses_buf[0], &statuses_buf[1],
-                                 &statuses_buf[2]};
     std::array<PinnableSlice, num_blobs> value_buf;
-    autovector<PinnableSlice*> values{&value_buf[0], &value_buf[1],
-                                      &value_buf[2]};
-    reader->MultiGetBlob(read_options, key_refs, offsets, sizes, statuses,
-                         values, &bytes_read);
+    std::array<BlobReadRequest, num_blobs> requests_buf;
+    autovector<BlobReadRequest*> blob_reqs;
+
+    for (size_t i = 0; i < num_blobs; ++i) {
+      requests_buf[i] =
+          BlobReadRequest(key_refs[i], offsets[i], blob_sizes[i],
+                          kNoCompression, &value_buf[i], &statuses_buf[i]);
+      blob_reqs.push_back(&requests_buf[i]);
+    }
+
+    reader->MultiGetBlob(read_options, blob_reqs, &bytes_read);
+
     for (size_t i = 0; i < num_blobs; ++i) {
       if (i == 1) {
         ASSERT_TRUE(statuses_buf[i].IsCorruption());
@@ -339,17 +345,21 @@ TEST_F(BlobFileReaderTest, CreateReaderAndGetBlob) {
     Slice wrong_key_slice(incorrect_key, sizeof(incorrect_key) - 1);
     key_refs[2] = std::cref(wrong_key_slice);
 
-    autovector<uint64_t> offsets{blob_offsets[0], blob_offsets[1],
-                                 blob_offsets[2]};
-    autovector<uint64_t> sizes{blob_sizes[0], blob_sizes[1], blob_sizes[2]};
     std::array<Status, num_blobs> statuses_buf;
-    autovector<Status*> statuses{&statuses_buf[0], &statuses_buf[1],
-                                 &statuses_buf[2]};
     std::array<PinnableSlice, num_blobs> value_buf;
-    autovector<PinnableSlice*> values{&value_buf[0], &value_buf[1],
-                                      &value_buf[2]};
-    reader->MultiGetBlob(read_options, key_refs, offsets, sizes, statuses,
-                         values, &bytes_read);
+    std::array<BlobReadRequest, num_blobs> requests_buf;
+
+    for (size_t i = 0; i < num_blobs; ++i) {
+      requests_buf[i] =
+          BlobReadRequest(key_refs[i], blob_offsets[i], blob_sizes[i],
+                          kNoCompression, &value_buf[i], &statuses_buf[i]);
+    }
+
+    autovector<BlobReadRequest*> blob_reqs = {
+        &requests_buf[0], &requests_buf[1], &requests_buf[2]};
+
+    reader->MultiGetBlob(read_options, blob_reqs, &bytes_read);
+
     for (size_t i = 0; i < num_blobs; ++i) {
       if (i == num_blobs - 1) {
         ASSERT_TRUE(statuses_buf[i].IsCorruption());
@@ -376,17 +386,26 @@ TEST_F(BlobFileReaderTest, CreateReaderAndGetBlob) {
     for (const auto& key_ref : keys) {
       key_refs.emplace_back(std::cref(key_ref));
     }
-    autovector<uint64_t> offsets{blob_offsets[0], blob_offsets[1],
-                                 blob_offsets[2]};
-    autovector<uint64_t> sizes{blob_sizes[0], blob_sizes[1] + 1, blob_sizes[2]};
+
     std::array<Status, num_blobs> statuses_buf;
-    autovector<Status*> statuses{&statuses_buf[0], &statuses_buf[1],
-                                 &statuses_buf[2]};
     std::array<PinnableSlice, num_blobs> value_buf;
-    autovector<PinnableSlice*> values{&value_buf[0], &value_buf[1],
-                                      &value_buf[2]};
-    reader->MultiGetBlob(read_options, key_refs, offsets, sizes, statuses,
-                         values, &bytes_read);
+    std::array<BlobReadRequest, num_blobs> requests_buf;
+
+    requests_buf[0] =
+        BlobReadRequest(key_refs[0], blob_offsets[0], blob_sizes[0],
+                        kNoCompression, &value_buf[0], &statuses_buf[0]);
+    requests_buf[1] =
+        BlobReadRequest(key_refs[1], blob_offsets[1], blob_sizes[1] + 1,
+                        kNoCompression, &value_buf[1], &statuses_buf[1]);
+    requests_buf[2] =
+        BlobReadRequest(key_refs[2], blob_offsets[2], blob_sizes[2],
+                        kNoCompression, &value_buf[2], &statuses_buf[2]);
+
+    autovector<BlobReadRequest*> blob_reqs = {
+        &requests_buf[0], &requests_buf[1], &requests_buf[2]};
+
+    reader->MultiGetBlob(read_options, blob_reqs, &bytes_read);
+
     for (size_t i = 0; i < num_blobs; ++i) {
       if (i != 1) {
         ASSERT_OK(statuses_buf[i]);

db/blob/blob_read_request.h

@@ -0,0 +1,58 @@
+//  Copyright (c) Meta Platforms, Inc. and affiliates.
+//  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 <cinttypes>
+
+#include "rocksdb/compression_type.h"
+#include "rocksdb/slice.h"
+#include "rocksdb/status.h"
+#include "util/autovector.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// A read Blob request structure for use in BlobSource::MultiGetBlob and
+// BlobFileReader::MultiGetBlob.
+struct BlobReadRequest {
+  // User key to lookup the paired blob
+  const Slice* user_key = nullptr;
+
+  // File offset in bytes
+  uint64_t offset = 0;
+
+  // Length to read in bytes
+  size_t len = 0;
+
+  // Blob compression type
+  CompressionType compression = kNoCompression;
+
+  // Output parameter set by MultiGetBlob() to point to the data buffer, and
+  // the number of valid bytes
+  PinnableSlice* result = nullptr;
+
+  // Status of read
+  Status* status = nullptr;
+
+  BlobReadRequest(const Slice& _user_key, uint64_t _offset, size_t _len,
+                  CompressionType _compression, PinnableSlice* _result,
+                  Status* _status)
+      : user_key(&_user_key),
+        offset(_offset),
+        len(_len),
+        compression(_compression),
+        result(_result),
+        status(_status) {}
+
+  BlobReadRequest() = default;
+  BlobReadRequest(const BlobReadRequest& other) = default;
+  BlobReadRequest& operator=(const BlobReadRequest& other) = default;
+};
+
+using BlobFileReadRequests =
+    std::tuple<uint64_t /* file_number */, uint64_t /* file_size */,
+               autovector<BlobReadRequest>>;
+
+}  // namespace ROCKSDB_NAMESPACE

db/blob/blob_source.cc

@@ -202,31 +202,51 @@ Status BlobSource::GetBlob(const ReadOptions& read_options,
   return s;
 }
 
-void BlobSource::MultiGetBlob(
-    const ReadOptions& read_options,
-    const autovector<std::reference_wrapper<const Slice>>& user_keys,
-    uint64_t file_number, uint64_t file_size,
-    const autovector<uint64_t>& offsets,
-    const autovector<uint64_t>& value_sizes, autovector<Status*>& statuses,
-    autovector<PinnableSlice*>& blobs, uint64_t* bytes_read) {
-  size_t num_blobs = user_keys.size();
+void BlobSource::MultiGetBlob(const ReadOptions& read_options,
+                              autovector<BlobFileReadRequests>& blob_reqs,
+                              uint64_t* bytes_read) {
+  assert(blob_reqs.size() > 0);
+
+  uint64_t total_bytes_read = 0;
+  uint64_t bytes_read_in_file = 0;
+
+  for (auto& [file_number, file_size, blob_reqs_in_file] : blob_reqs) {
+    // sort blob_reqs_in_file by file offset.
+    std::sort(
+        blob_reqs_in_file.begin(), blob_reqs_in_file.end(),
+        [](const BlobReadRequest& lhs, const BlobReadRequest& rhs) -> bool {
+          return lhs.offset < rhs.offset;
+        });
+
+    MultiGetBlobFromOneFile(read_options, file_number, file_size,
+                            blob_reqs_in_file, &bytes_read_in_file);
+
+    total_bytes_read += bytes_read_in_file;
+  }
+
+  if (bytes_read) {
+    *bytes_read = total_bytes_read;
+  }
+}
+
+void BlobSource::MultiGetBlobFromOneFile(const ReadOptions& read_options,
+                                         uint64_t file_number,
+                                         uint64_t file_size,
+                                         autovector<BlobReadRequest>& blob_reqs,
+                                         uint64_t* bytes_read) {
+  const size_t num_blobs = blob_reqs.size();
   assert(num_blobs > 0);
   assert(num_blobs <= MultiGetContext::MAX_BATCH_SIZE);
-  assert(num_blobs == offsets.size());
-  assert(num_blobs == value_sizes.size());
-  assert(num_blobs == statuses.size());
-  assert(num_blobs == blobs.size());
 
 #ifndef NDEBUG
-  for (size_t i = 0; i < offsets.size() - 1; ++i) {
-    assert(offsets[i] <= offsets[i + 1]);
+  for (size_t i = 0; i < num_blobs - 1; ++i) {
+    assert(blob_reqs[i].offset <= blob_reqs[i + 1].offset);
   }
 #endif  // !NDEBUG
 
   using Mask = uint64_t;
   Mask cache_hit_mask = 0;
 
-  Status s;
   uint64_t total_bytes = 0;
   const OffsetableCacheKey base_cache_key(db_id_, db_session_id_, file_number,
                                           file_size);
@@ -234,15 +254,18 @@ void BlobSource::MultiGetBlob(
   if (blob_cache_) {
     size_t cached_blob_count = 0;
     for (size_t i = 0; i < num_blobs; ++i) {
+      auto& req = blob_reqs[i];
+
       CachableEntry<std::string> blob_entry;
-      const CacheKey cache_key = base_cache_key.WithOffset(offsets[i]);
+      const CacheKey cache_key = base_cache_key.WithOffset(req.offset);
       const Slice key = cache_key.AsSlice();
 
-      s = GetBlobFromCache(key, &blob_entry);
+      const Status s = GetBlobFromCache(key, &blob_entry);
+
       if (s.ok() && blob_entry.GetValue()) {
-        assert(statuses[i]);
-        *statuses[i] = s;
-        blobs[i]->PinSelf(*blob_entry.GetValue());
+        assert(req.status);
+        *req.status = s;
+        req.result->PinSelf(*blob_entry.GetValue());
 
         // Update the counter for the number of valid blobs read from the cache.
         ++cached_blob_count;
@@ -251,10 +274,10 @@ void BlobSource::MultiGetBlob(
         uint64_t adjustment =
             read_options.verify_checksums
                 ? BlobLogRecord::CalculateAdjustmentForRecordHeader(
-                      user_keys[i].get().size())
+                      req.user_key->size())
                 : 0;
-        assert(offsets[i] >= adjustment);
-        total_bytes += value_sizes[i] + adjustment;
+        assert(req.offset >= adjustment);
+        total_bytes += req.len + adjustment;
         cache_hit_mask |= (Mask{1} << i);  // cache hit
       }
     }
@@ -272,8 +295,8 @@ void BlobSource::MultiGetBlob(
   if (no_io) {
     for (size_t i = 0; i < num_blobs; ++i) {
       if (!(cache_hit_mask & (Mask{1} << i))) {
-        assert(statuses[i]);
-        *statuses[i] =
+        assert(blob_reqs[i].status);
+        *blob_reqs[i].status =
             Status::Incomplete("Cannot read blob(s): no disk I/O allowed");
       }
     }
@@ -282,50 +305,43 @@ void BlobSource::MultiGetBlob(
 
   {
     // Find the rest of blobs from the file since I/O is allowed.
-    autovector<std::reference_wrapper<const Slice>> _user_keys;
-    autovector<uint64_t> _offsets;
-    autovector<uint64_t> _value_sizes;
-    autovector<Status*> _statuses;
-    autovector<PinnableSlice*> _blobs;
+    autovector<BlobReadRequest*> _blob_reqs;
     uint64_t _bytes_read = 0;
 
     for (size_t i = 0; i < num_blobs; ++i) {
       if (!(cache_hit_mask & (Mask{1} << i))) {
-        _user_keys.emplace_back(user_keys[i]);
-        _offsets.push_back(offsets[i]);
-        _value_sizes.push_back(value_sizes[i]);
-        _statuses.push_back(statuses[i]);
-        _blobs.push_back(blobs[i]);
+        _blob_reqs.push_back(&blob_reqs[i]);
       }
     }
 
     CacheHandleGuard<BlobFileReader> blob_file_reader;
-    s = blob_file_cache_->GetBlobFileReader(file_number, &blob_file_reader);
+    Status s =
+        blob_file_cache_->GetBlobFileReader(file_number, &blob_file_reader);
     if (!s.ok()) {
-      for (size_t i = 0; i < _blobs.size(); ++i) {
-        assert(_statuses[i]);
-        *_statuses[i] = s;
+      for (size_t i = 0; i < _blob_reqs.size(); ++i) {
+        assert(_blob_reqs[i]->status);
+        *_blob_reqs[i]->status = s;
       }
       return;
     }
 
     assert(blob_file_reader.GetValue());
 
-    blob_file_reader.GetValue()->MultiGetBlob(read_options, _user_keys,
-                                              _offsets, _value_sizes, _statuses,
-                                              _blobs, &_bytes_read);
+    blob_file_reader.GetValue()->MultiGetBlob(read_options, _blob_reqs,
+                                              &_bytes_read);
 
-    if (read_options.fill_cache) {
+    if (blob_cache_ && read_options.fill_cache) {
       // If filling cache is allowed and a cache is configured, try to put
       // the blob(s) to the cache.
-      for (size_t i = 0; i < _blobs.size(); ++i) {
-        if (_statuses[i]->ok()) {
+      for (size_t i = 0; i < _blob_reqs.size(); ++i) {
+        if (_blob_reqs[i]->status->ok()) {
           CachableEntry<std::string> blob_entry;
-          const CacheKey cache_key = base_cache_key.WithOffset(_offsets[i]);
+          const CacheKey cache_key =
+              base_cache_key.WithOffset(_blob_reqs[i]->offset);
           const Slice key = cache_key.AsSlice();
-          s = PutBlobIntoCache(key, &blob_entry, _blobs[i]);
+          s = PutBlobIntoCache(key, &blob_entry, _blob_reqs[i]->result);
           if (!s.ok()) {
-            *_statuses[i] = s;
+            *_blob_reqs[i]->status = s;
           }
         }
       }

db/blob/blob_source.h

@@ -10,6 +10,7 @@
 #include "cache/cache_helpers.h"
 #include "cache/cache_key.h"
 #include "db/blob/blob_file_cache.h"
+#include "db/blob/blob_read_request.h"
 #include "rocksdb/cache.h"
 #include "rocksdb/rocksdb_namespace.h"
 #include "table/block_based/cachable_entry.h"
@@ -37,7 +38,7 @@ class BlobSource {
 
   ~BlobSource();
 
-  // Read a blob from the underlying cache or storage.
+  // Read a blob from the underlying cache or one blob file.
   //
   // If successful, returns ok and sets "*value" to the newly retrieved
   // uncompressed blob. If there was an error while fetching the blob, sets
@@ -52,25 +53,44 @@ class BlobSource {
                  FilePrefetchBuffer* prefetch_buffer, PinnableSlice* value,
                  uint64_t* bytes_read);
 
-  // Read multiple blobs from the underlying cache or storage.
+  // Read multiple blobs from the underlying cache or blob file(s).
   //
-  // If successful, returns ok and sets the elements of blobs to the newly
-  // retrieved uncompressed blobs. If there was an error while fetching one of
-  // blobs, sets its corresponding "blobs[i]" to empty and sets "statuses[i]" to
-  // a non-ok status.
+  // If successful, returns ok and sets "result" in the elements of "blob_reqs"
+  // to the newly retrieved uncompressed blobs. If there was an error while
+  // fetching one of blobs, sets its "result" to empty and sets its
+  // corresponding "status" to a non-ok status.
   //
   // Note:
-  //  - Offsets must be sorted in ascending order by caller.
+  //  - The main difference between this function and MultiGetBlobFromOneFile is
+  //    that this function can read multiple blobs from multiple blob files.
+  //
   //  - For consistency, whether the blob is found in the cache or on disk, sets
   //  "*bytes_read" to the total size of on-disk (possibly compressed) blob
   //  records.
-  void MultiGetBlob(
-      const ReadOptions& read_options,
-      const autovector<std::reference_wrapper<const Slice>>& user_keys,
+  void MultiGetBlob(const ReadOptions& read_options,
+                    autovector<BlobFileReadRequests>& blob_reqs,
+                    uint64_t* bytes_read);
+
+  // Read multiple blobs from the underlying cache or one blob file.
+  //
+  // If successful, returns ok and sets "result" in the elements of "blob_reqs"
+  // to the newly retrieved uncompressed blobs. If there was an error while
+  // fetching one of blobs, sets its "result" to empty and sets its
+  // corresponding "status" to a non-ok status.
+  //
+  // Note:
+  //  - The main difference between this function and MultiGetBlob is that this
+  //  function is only used for the case where the demanded blobs are stored in
+  //  one blob file. MultiGetBlob will call this function multiple times if the
+  //  demanded blobs are stored in multiple blob files.
+  //
+  //  - For consistency, whether the blob is found in the cache or on disk, sets
+  //  "*bytes_read" to the total size of on-disk (possibly compressed) blob
+  //  records.
+  void MultiGetBlobFromOneFile(const ReadOptions& read_options,
                                uint64_t file_number, uint64_t file_size,
-      const autovector<uint64_t>& offsets,
-      const autovector<uint64_t>& value_sizes, autovector<Status*>& statuses,
-      autovector<PinnableSlice*>& blobs, uint64_t* bytes_read);
+                               autovector<BlobReadRequest>& blob_reqs,
+                               uint64_t* bytes_read);
 
   inline Status GetBlobFileReader(
       uint64_t blob_file_number,

db/blob/blob_source_test.cc

@@ -561,6 +561,199 @@ TEST_F(BlobSourceTest, GetCompressedBlobs) {
   }
 }
 
+TEST_F(BlobSourceTest, MultiGetBlobsFromMultiFiles) {
+  options_.cf_paths.emplace_back(
+      test::PerThreadDBPath(env_, "BlobSourceTest_MultiGetBlobsFromMultiFiles"),
+      0);
+
+  options_.statistics = CreateDBStatistics();
+  Statistics* statistics = options_.statistics.get();
+  assert(statistics);
+
+  DestroyAndReopen(options_);
+
+  ImmutableOptions immutable_options(options_);
+
+  constexpr uint32_t column_family_id = 1;
+  constexpr bool has_ttl = false;
+  constexpr ExpirationRange expiration_range;
+  constexpr uint64_t blob_files = 2;
+  constexpr size_t num_blobs = 32;
+
+  std::vector<std::string> key_strs;
+  std::vector<std::string> blob_strs;
+
+  for (size_t i = 0; i < num_blobs; ++i) {
+    key_strs.push_back("key" + std::to_string(i));
+    blob_strs.push_back("blob" + std::to_string(i));
+  }
+
+  std::vector<Slice> keys;
+  std::vector<Slice> blobs;
+
+  uint64_t file_size = BlobLogHeader::kSize;
+  uint64_t blob_value_bytes = 0;
+  for (size_t i = 0; i < num_blobs; ++i) {
+    keys.push_back({key_strs[i]});
+    blobs.push_back({blob_strs[i]});
+    blob_value_bytes += blobs[i].size();
+    file_size += BlobLogRecord::kHeaderSize + keys[i].size() + blobs[i].size();
+  }
+  file_size += BlobLogFooter::kSize;
+  const uint64_t blob_records_bytes =
+      file_size - BlobLogHeader::kSize - BlobLogFooter::kSize;
+
+  std::vector<uint64_t> blob_offsets(keys.size());
+  std::vector<uint64_t> blob_sizes(keys.size());
+
+  {
+    // Write key/blob pairs to multiple blob files.
+    for (size_t i = 0; i < blob_files; ++i) {
+      const uint64_t file_number = i + 1;
+      WriteBlobFile(immutable_options, column_family_id, has_ttl,
+                    expiration_range, expiration_range, file_number, keys,
+                    blobs, kNoCompression, blob_offsets, blob_sizes);
+    }
+  }
+
+  constexpr size_t capacity = 10;
+  std::shared_ptr<Cache> backing_cache =
+      NewLRUCache(capacity);  // Blob file cache
+
+  FileOptions file_options;
+  constexpr HistogramImpl* blob_file_read_hist = nullptr;
+
+  std::unique_ptr<BlobFileCache> blob_file_cache(new BlobFileCache(
+      backing_cache.get(), &immutable_options, &file_options, column_family_id,
+      blob_file_read_hist, nullptr /*IOTracer*/));
+
+  BlobSource blob_source(&immutable_options, db_id_, db_session_id_,
+                         blob_file_cache.get());
+
+  ReadOptions read_options;
+  read_options.verify_checksums = true;
+
+  uint64_t bytes_read = 0;
+
+  {
+    // MultiGetBlob
+    read_options.fill_cache = true;
+    read_options.read_tier = ReadTier::kReadAllTier;
+
+    autovector<BlobFileReadRequests> blob_reqs;
+    std::array<autovector<BlobReadRequest>, blob_files> blob_reqs_in_file;
+    std::array<PinnableSlice, num_blobs * blob_files> value_buf;
+    std::array<Status, num_blobs * blob_files> statuses_buf;
+
+    for (size_t i = 0; i < blob_files; ++i) {
+      const uint64_t file_number = i + 1;
+      for (size_t j = 0; j < num_blobs; ++j) {
+        blob_reqs_in_file[i].emplace_back(
+            keys[j], blob_offsets[j], blob_sizes[j], kNoCompression,
+            &value_buf[i * num_blobs + j], &statuses_buf[i * num_blobs + j]);
+      }
+      blob_reqs.emplace_back(file_number, file_size, blob_reqs_in_file[i]);
+    }
+
+    get_perf_context()->Reset();
+    statistics->Reset().PermitUncheckedError();
+
+    blob_source.MultiGetBlob(read_options, blob_reqs, &bytes_read);
+
+    for (size_t i = 0; i < blob_files; ++i) {
+      const uint64_t file_number = i + 1;
+      for (size_t j = 0; j < num_blobs; ++j) {
+        ASSERT_OK(statuses_buf[i * num_blobs + j]);
+        ASSERT_EQ(value_buf[i * num_blobs + j], blobs[j]);
+        ASSERT_TRUE(blob_source.TEST_BlobInCache(file_number, file_size,
+                                                 blob_offsets[j]));
+      }
+    }
+
+    // Retrieved all blobs from 2 blob files twice via MultiGetBlob and
+    // TEST_BlobInCache.
+    ASSERT_EQ((int)get_perf_context()->blob_cache_hit_count,
+              num_blobs * blob_files);
+    ASSERT_EQ((int)get_perf_context()->blob_read_count,
+              num_blobs * blob_files);  // blocking i/o
+    ASSERT_EQ((int)get_perf_context()->blob_read_byte,
+              blob_records_bytes * blob_files);  // blocking i/o
+    ASSERT_GE((int)get_perf_context()->blob_checksum_time, 0);
+    ASSERT_EQ((int)get_perf_context()->blob_decompress_time, 0);
+
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_MISS),
+              num_blobs * blob_files);  // MultiGetBlob
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_HIT),
+              num_blobs * blob_files);  // TEST_BlobInCache
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_ADD),
+              num_blobs * blob_files);  // MultiGetBlob
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_BYTES_READ),
+              blob_value_bytes * blob_files);  // TEST_BlobInCache
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_BYTES_WRITE),
+              blob_value_bytes * blob_files);  // MultiGetBlob
+
+    get_perf_context()->Reset();
+    statistics->Reset().PermitUncheckedError();
+
+    autovector<BlobReadRequest> fake_blob_reqs_in_file;
+    std::array<PinnableSlice, num_blobs> fake_value_buf;
+    std::array<Status, num_blobs> fake_statuses_buf;
+
+    const uint64_t fake_file_number = 100;
+    for (size_t i = 0; i < num_blobs; ++i) {
+      fake_blob_reqs_in_file.emplace_back(
+          keys[i], blob_offsets[i], blob_sizes[i], kNoCompression,
+          &fake_value_buf[i], &fake_statuses_buf[i]);
+    }
+
+    // Add a fake multi-get blob request.
+    blob_reqs.emplace_back(fake_file_number, file_size, fake_blob_reqs_in_file);
+
+    blob_source.MultiGetBlob(read_options, blob_reqs, &bytes_read);
+
+    // Check the real blob read requests.
+    for (size_t i = 0; i < blob_files; ++i) {
+      const uint64_t file_number = i + 1;
+      for (size_t j = 0; j < num_blobs; ++j) {
+        ASSERT_OK(statuses_buf[i * num_blobs + j]);
+        ASSERT_EQ(value_buf[i * num_blobs + j], blobs[j]);
+        ASSERT_TRUE(blob_source.TEST_BlobInCache(file_number, file_size,
+                                                 blob_offsets[j]));
+      }
+    }
+
+    // Check the fake blob request.
+    for (size_t i = 0; i < num_blobs; ++i) {
+      ASSERT_TRUE(fake_statuses_buf[i].IsIOError());
+      ASSERT_TRUE(fake_value_buf[i].empty());
+      ASSERT_FALSE(blob_source.TEST_BlobInCache(fake_file_number, file_size,
+                                                blob_offsets[i]));
+    }
+
+    // Retrieved all blobs from 3 blob files (including the fake one) twice
+    // via MultiGetBlob and TEST_BlobInCache.
+    ASSERT_EQ((int)get_perf_context()->blob_cache_hit_count,
+              num_blobs * blob_files * 2);
+    ASSERT_EQ((int)get_perf_context()->blob_read_count,
+              0);  // blocking i/o
+    ASSERT_EQ((int)get_perf_context()->blob_read_byte,
+              0);  // blocking i/o
+    ASSERT_GE((int)get_perf_context()->blob_checksum_time, 0);
+    ASSERT_EQ((int)get_perf_context()->blob_decompress_time, 0);
+
+    // Fake blob requests: MultiGetBlob and TEST_BlobInCache
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_MISS), num_blobs * 2);
+    // Real blob requests: MultiGetBlob and TEST_BlobInCache
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_HIT),
+              num_blobs * blob_files * 2);
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_ADD), 0);
+    // Real blob requests: MultiGetBlob and TEST_BlobInCache
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_BYTES_READ),
+              blob_value_bytes * blob_files * 2);
+    ASSERT_EQ(statistics->getTickerCount(BLOB_DB_CACHE_BYTES_WRITE), 0);
+  }
+}
+
 TEST_F(BlobSourceTest, MultiGetBlobsFromCache) {
   options_.cf_paths.emplace_back(
       test::PerThreadDBPath(env_, "BlobSourceTest_MultiGetBlobsFromCache"), 0);
@@ -625,23 +818,15 @@ TEST_F(BlobSourceTest, MultiGetBlobsFromCache) {
   constexpr FilePrefetchBuffer* prefetch_buffer = nullptr;
 
   {
-    // MultiGetBlob
+    // MultiGetBlobFromOneFile
     uint64_t bytes_read = 0;
-
-    autovector<std::reference_wrapper<const Slice>> key_refs;
-    autovector<uint64_t> offsets;
-    autovector<uint64_t> sizes;
     std::array<Status, num_blobs> statuses_buf;
-    autovector<Status*> statuses;
     std::array<PinnableSlice, num_blobs> value_buf;
-    autovector<PinnableSlice*> values;
+    autovector<BlobReadRequest> blob_reqs;
 
     for (size_t i = 0; i < num_blobs; i += 2) {  // even index
-      key_refs.emplace_back(std::cref(keys[i]));
-      offsets.push_back(blob_offsets[i]);
-      sizes.push_back(blob_sizes[i]);
-      statuses.push_back(&statuses_buf[i]);
-      values.push_back(&value_buf[i]);
+      blob_reqs.emplace_back(keys[i], blob_offsets[i], blob_sizes[i],
+                             kNoCompression, &value_buf[i], &statuses_buf[i]);
       ASSERT_FALSE(blob_source.TEST_BlobInCache(blob_file_number, file_size,
                                                 blob_offsets[i]));
     }
@@ -652,9 +837,8 @@ TEST_F(BlobSourceTest, MultiGetBlobsFromCache) {
     statistics->Reset().PermitUncheckedError();
 
     // Get half of blobs
-    blob_source.MultiGetBlob(read_options, key_refs, blob_file_number,
-                             file_size, offsets, sizes, statuses, values,
-                             &bytes_read);
+    blob_source.MultiGetBlobFromOneFile(read_options, blob_file_number,
+                                        file_size, blob_reqs, &bytes_read);
 
     uint64_t fs_read_bytes = 0;
     uint64_t ca_read_bytes = 0;
@@ -709,27 +893,19 @@ TEST_F(BlobSourceTest, MultiGetBlobsFromCache) {
                                                blob_offsets[i]));
     }
 
-    // Cache-only MultiGetBlob
+    // Cache-only MultiGetBlobFromOneFile
     read_options.read_tier = ReadTier::kBlockCacheTier;
     get_perf_context()->Reset();
     statistics->Reset().PermitUncheckedError();
 
-    key_refs.clear();
-    offsets.clear();
-    sizes.clear();
-    statuses.clear();
-    values.clear();
+    blob_reqs.clear();
     for (size_t i = 0; i < num_blobs; ++i) {
-      key_refs.emplace_back(std::cref(keys[i]));
-      offsets.push_back(blob_offsets[i]);
-      sizes.push_back(blob_sizes[i]);
-      statuses.push_back(&statuses_buf[i]);
-      values.push_back(&value_buf[i]);
+      blob_reqs.emplace_back(keys[i], blob_offsets[i], blob_sizes[i],
+                             kNoCompression, &value_buf[i], &statuses_buf[i]);
     }
 
-    blob_source.MultiGetBlob(read_options, key_refs, blob_file_number,
-                             file_size, offsets, sizes, statuses, values,
-                             &bytes_read);
+    blob_source.MultiGetBlobFromOneFile(read_options, blob_file_number,
+                                        file_size, blob_reqs, &bytes_read);
 
     uint64_t blob_bytes = 0;
     for (size_t i = 0; i < num_blobs; ++i) {
@@ -759,24 +935,17 @@ TEST_F(BlobSourceTest, MultiGetBlobsFromCache) {
   options_.blob_cache->EraseUnRefEntries();
 
   {
-    // Cache-only MultiGetBlob
+    // Cache-only MultiGetBlobFromOneFile
     uint64_t bytes_read = 0;
     read_options.read_tier = ReadTier::kBlockCacheTier;
 
-    autovector<std::reference_wrapper<const Slice>> key_refs;
-    autovector<uint64_t> offsets;
-    autovector<uint64_t> sizes;
     std::array<Status, num_blobs> statuses_buf;
-    autovector<Status*> statuses;
     std::array<PinnableSlice, num_blobs> value_buf;
-    autovector<PinnableSlice*> values;
+    autovector<BlobReadRequest> blob_reqs;
 
     for (size_t i = 0; i < num_blobs; i++) {
-      key_refs.emplace_back(std::cref(keys[i]));
-      offsets.push_back(blob_offsets[i]);
-      sizes.push_back(blob_sizes[i]);
-      statuses.push_back(&statuses_buf[i]);
-      values.push_back(&value_buf[i]);
+      blob_reqs.emplace_back(keys[i], blob_offsets[i], blob_sizes[i],
+                             kNoCompression, &value_buf[i], &statuses_buf[i]);
       ASSERT_FALSE(blob_source.TEST_BlobInCache(blob_file_number, file_size,
                                                 blob_offsets[i]));
     }
@@ -784,9 +953,8 @@ TEST_F(BlobSourceTest, MultiGetBlobsFromCache) {
     get_perf_context()->Reset();
     statistics->Reset().PermitUncheckedError();
 
-    blob_source.MultiGetBlob(read_options, key_refs, blob_file_number,
-                             file_size, offsets, sizes, statuses, values,
-                             &bytes_read);
+    blob_source.MultiGetBlobFromOneFile(read_options, blob_file_number,
+                                        file_size, blob_reqs, &bytes_read);
 
     for (size_t i = 0; i < num_blobs; ++i) {
       ASSERT_TRUE(statuses_buf[i].IsIncomplete());
@@ -809,40 +977,33 @@ TEST_F(BlobSourceTest, MultiGetBlobsFromCache) {
   }
 
   {
-    // MultiGetBlob from non-existing file
+    // MultiGetBlobFromOneFile from non-existing file
     uint64_t bytes_read = 0;
-    uint64_t file_number = 100;  // non-existing file
+    uint64_t non_existing_file_number = 100;
     read_options.read_tier = ReadTier::kReadAllTier;
 
-    autovector<std::reference_wrapper<const Slice>> key_refs;
-    autovector<uint64_t> offsets;
-    autovector<uint64_t> sizes;
     std::array<Status, num_blobs> statuses_buf;
-    autovector<Status*> statuses;
     std::array<PinnableSlice, num_blobs> value_buf;
-    autovector<PinnableSlice*> values;
+    autovector<BlobReadRequest> blob_reqs;
 
     for (size_t i = 0; i < num_blobs; i++) {
-      key_refs.emplace_back(std::cref(keys[i]));
-      offsets.push_back(blob_offsets[i]);
-      sizes.push_back(blob_sizes[i]);
-      statuses.push_back(&statuses_buf[i]);
-      values.push_back(&value_buf[i]);
-      ASSERT_FALSE(blob_source.TEST_BlobInCache(file_number, file_size,
-                                                blob_offsets[i]));
+      blob_reqs.emplace_back(keys[i], blob_offsets[i], blob_sizes[i],
+                             kNoCompression, &value_buf[i], &statuses_buf[i]);
+      ASSERT_FALSE(blob_source.TEST_BlobInCache(non_existing_file_number,
+                                                file_size, blob_offsets[i]));
     }
 
     get_perf_context()->Reset();
     statistics->Reset().PermitUncheckedError();
 
-    blob_source.MultiGetBlob(read_options, key_refs, file_number, file_size,
-                             offsets, sizes, statuses, values, &bytes_read);
+    blob_source.MultiGetBlobFromOneFile(read_options, non_existing_file_number,
+                                        file_size, blob_reqs, &bytes_read);
 
     for (size_t i = 0; i < num_blobs; ++i) {
       ASSERT_TRUE(statuses_buf[i].IsIOError());
       ASSERT_TRUE(value_buf[i].empty());
-      ASSERT_FALSE(blob_source.TEST_BlobInCache(file_number, file_size,
-                                                blob_offsets[i]));
+      ASSERT_FALSE(blob_source.TEST_BlobInCache(non_existing_file_number,
+                                                file_size, blob_offsets[i]));
     }
 
     ASSERT_EQ((int)get_perf_context()->blob_cache_hit_count, 0);

db/blob/db_blob_basic_test.cc

@@ -299,6 +299,141 @@ TEST_F(DBBlobBasicTest, MultiGetBlobs) {
   }
 }
 
+TEST_F(DBBlobBasicTest, MultiGetBlobsFromCache) {
+  Options options = GetDefaultOptions();
+
+  LRUCacheOptions co;
+  co.capacity = 2048;
+  co.num_shard_bits = 2;
+  co.metadata_charge_policy = kDontChargeCacheMetadata;
+  auto backing_cache = NewLRUCache(co);
+
+  constexpr size_t min_blob_size = 6;
+  options.min_blob_size = min_blob_size;
+  options.create_if_missing = true;
+  options.enable_blob_files = true;
+  options.blob_cache = backing_cache;
+
+  BlockBasedTableOptions block_based_options;
+  block_based_options.no_block_cache = false;
+  block_based_options.block_cache = backing_cache;
+  block_based_options.cache_index_and_filter_blocks = true;
+  options.table_factory.reset(NewBlockBasedTableFactory(block_based_options));
+
+  DestroyAndReopen(options);
+
+  // Put then retrieve three key-values. The first value is below the size limit
+  // and is thus stored inline; the other two are stored separately as blobs.
+  constexpr size_t num_keys = 3;
+
+  constexpr char first_key[] = "first_key";
+  constexpr char first_value[] = "short";
+  static_assert(sizeof(first_value) - 1 < min_blob_size,
+                "first_value too long to be inlined");
+
+  ASSERT_OK(Put(first_key, first_value));
+
+  constexpr char second_key[] = "second_key";
+  constexpr char second_value[] = "long_value";
+  static_assert(sizeof(second_value) - 1 >= min_blob_size,
+                "second_value too short to be stored as blob");
+
+  ASSERT_OK(Put(second_key, second_value));
+
+  constexpr char third_key[] = "third_key";
+  constexpr char third_value[] = "other_long_value";
+  static_assert(sizeof(third_value) - 1 >= min_blob_size,
+                "third_value too short to be stored as blob");
+
+  ASSERT_OK(Put(third_key, third_value));
+
+  ASSERT_OK(Flush());
+
+  ReadOptions read_options;
+  read_options.fill_cache = false;
+
+  std::array<Slice, num_keys> keys{{first_key, second_key, third_key}};
+
+  {
+    std::array<PinnableSlice, num_keys> values;
+    std::array<Status, num_keys> statuses;
+
+    db_->MultiGet(read_options, db_->DefaultColumnFamily(), num_keys, &keys[0],
+                  &values[0], &statuses[0]);
+
+    ASSERT_OK(statuses[0]);
+    ASSERT_EQ(values[0], first_value);
+
+    ASSERT_OK(statuses[1]);
+    ASSERT_EQ(values[1], second_value);
+
+    ASSERT_OK(statuses[2]);
+    ASSERT_EQ(values[2], third_value);
+  }
+
+  // Try again with no I/O allowed. The first (inlined) value should be
+  // successfully read; however, the two blob values could only be read from the
+  // blob file, so for those the read should return Incomplete.
+  read_options.read_tier = kBlockCacheTier;
+
+  {
+    std::array<PinnableSlice, num_keys> values;
+    std::array<Status, num_keys> statuses;
+
+    db_->MultiGet(read_options, db_->DefaultColumnFamily(), num_keys, &keys[0],
+                  &values[0], &statuses[0]);
+
+    ASSERT_OK(statuses[0]);
+    ASSERT_EQ(values[0], first_value);
+
+    ASSERT_TRUE(statuses[1].IsIncomplete());
+
+    ASSERT_TRUE(statuses[2].IsIncomplete());
+  }
+
+  // Fill the cache when reading blobs from the blob file.
+  read_options.read_tier = kReadAllTier;
+  read_options.fill_cache = true;
+
+  {
+    std::array<PinnableSlice, num_keys> values;
+    std::array<Status, num_keys> statuses;
+
+    db_->MultiGet(read_options, db_->DefaultColumnFamily(), num_keys, &keys[0],
+                  &values[0], &statuses[0]);
+
+    ASSERT_OK(statuses[0]);
+    ASSERT_EQ(values[0], first_value);
+
+    ASSERT_OK(statuses[1]);
+    ASSERT_EQ(values[1], second_value);
+
+    ASSERT_OK(statuses[2]);
+    ASSERT_EQ(values[2], third_value);
+  }
+
+  // Try again with no I/O allowed. All blobs should be successfully read from
+  // the cache.
+  read_options.read_tier = kBlockCacheTier;
+
+  {
+    std::array<PinnableSlice, num_keys> values;
+    std::array<Status, num_keys> statuses;
+
+    db_->MultiGet(read_options, db_->DefaultColumnFamily(), num_keys, &keys[0],
+                  &values[0], &statuses[0]);
+
+    ASSERT_OK(statuses[0]);
+    ASSERT_EQ(values[0], first_value);
+
+    ASSERT_OK(statuses[1]);
+    ASSERT_EQ(values[1], second_value);
+
+    ASSERT_OK(statuses[2]);
+    ASSERT_EQ(values[2], third_value);
+  }
+}
+
 #ifndef ROCKSDB_LITE
 TEST_F(DBBlobBasicTest, MultiGetWithDirectIO) {
   Options options = GetDefaultOptions();
@@ -492,8 +627,23 @@ TEST_F(DBBlobBasicTest, MultiGetWithDirectIO) {
 
 TEST_F(DBBlobBasicTest, MultiGetBlobsFromMultipleFiles) {
   Options options = GetDefaultOptions();
-  options.enable_blob_files = true;
+
+  LRUCacheOptions co;
+  co.capacity = 2 << 20; // 2MB
+  co.num_shard_bits = 2;
+  co.metadata_charge_policy = kDontChargeCacheMetadata;
+  auto backing_cache = NewLRUCache(co);
+
   options.min_blob_size = 0;
+  options.create_if_missing = true;
+  options.enable_blob_files = true;
+  options.blob_cache = backing_cache;
+
+  BlockBasedTableOptions block_based_options;
+  block_based_options.no_block_cache = false;
+  block_based_options.block_cache = backing_cache;
+  block_based_options.cache_index_and_filter_blocks = true;
+  options.table_factory.reset(NewBlockBasedTableFactory(block_based_options));
 
   Reopen(options);
 
@@ -519,9 +669,15 @@ TEST_F(DBBlobBasicTest, MultiGetBlobsFromMultipleFiles) {
   for (size_t i = 0; i < keys.size(); ++i) {
     keys[i] = key_strs[i];
   }
+
+  ReadOptions read_options;
+  read_options.read_tier = kReadAllTier;
+  read_options.fill_cache = false;
+
+  {
     std::array<PinnableSlice, kNumKeys> values;
     std::array<Status, kNumKeys> statuses;
-  db_->MultiGet(ReadOptions(), db_->DefaultColumnFamily(), kNumKeys, &keys[0],
+    db_->MultiGet(read_options, db_->DefaultColumnFamily(), kNumKeys, &keys[0],
                   &values[0], &statuses[0]);
 
     for (size_t i = 0; i < kNumKeys; ++i) {
@@ -530,6 +686,50 @@ TEST_F(DBBlobBasicTest, MultiGetBlobsFromMultipleFiles) {
     }
   }
 
+  read_options.read_tier = kBlockCacheTier;
+
+  {
+    std::array<PinnableSlice, kNumKeys> values;
+    std::array<Status, kNumKeys> statuses;
+    db_->MultiGet(read_options, db_->DefaultColumnFamily(), kNumKeys, &keys[0],
+                  &values[0], &statuses[0]);
+
+    for (size_t i = 0; i < kNumKeys; ++i) {
+      ASSERT_TRUE(statuses[i].IsIncomplete());
+      ASSERT_TRUE(values[i].empty());
+    }
+  }
+
+  read_options.read_tier = kReadAllTier;
+  read_options.fill_cache = true;
+
+  {
+    std::array<PinnableSlice, kNumKeys> values;
+    std::array<Status, kNumKeys> statuses;
+    db_->MultiGet(read_options, db_->DefaultColumnFamily(), kNumKeys, &keys[0],
+                  &values[0], &statuses[0]);
+
+    for (size_t i = 0; i < kNumKeys; ++i) {
+      ASSERT_OK(statuses[i]);
+      ASSERT_EQ(value_strs[i], values[i]);
+    }
+  }
+
+  read_options.read_tier = kBlockCacheTier;
+
+  {
+    std::array<PinnableSlice, kNumKeys> values;
+    std::array<Status, kNumKeys> statuses;
+    db_->MultiGet(read_options, db_->DefaultColumnFamily(), kNumKeys, &keys[0],
+                  &values[0], &statuses[0]);
+
+    for (size_t i = 0; i < kNumKeys; ++i) {
+      ASSERT_OK(statuses[i]);
+      ASSERT_EQ(value_strs[i], values[i]);
+    }
+  }
+}
+
 TEST_F(DBBlobBasicTest, GetBlob_CorruptIndex) {
   Options options = GetDefaultOptions();
   options.enable_blob_files = true;

db/version_set.cc

@@ -1907,114 +1907,62 @@ Status Version::GetBlob(const ReadOptions& read_options, const Slice& user_key,
 
 void Version::MultiGetBlob(
     const ReadOptions& read_options, MultiGetRange& range,
-    std::unordered_map<uint64_t, BlobReadRequests>& blob_rqs) {
-  if (read_options.read_tier == kBlockCacheTier) {
-    Status s = Status::Incomplete("Cannot read blob(s): no disk I/O allowed");
-    for (const auto& elem : blob_rqs) {
-      for (const auto& blob_rq : elem.second) {
-        const KeyContext& key_context = blob_rq.second;
-        assert(key_context.s);
-        assert(key_context.s->ok());
-        *(key_context.s) = s;
-        assert(key_context.get_context);
-        auto& get_context = *(key_context.get_context);
-        get_context.MarkKeyMayExist();
-      }
-    }
-    return;
-  }
+    std::unordered_map<uint64_t, BlobReadContexts>& blob_ctxs) {
+  assert(!blob_ctxs.empty());
 
-  assert(!blob_rqs.empty());
-  Status status;
+  autovector<BlobFileReadRequests> blob_reqs;
 
-  for (auto& elem : blob_rqs) {
-    const uint64_t blob_file_number = elem.first;
+  for (auto& ctx : blob_ctxs) {
+    const auto file_number = ctx.first;
+    const auto blob_file_meta = storage_info_.GetBlobFileMetaData(file_number);
 
-    if (!storage_info_.GetBlobFileMetaData(blob_file_number)) {
-      auto& blobs_in_file = elem.second;
+    autovector<BlobReadRequest> blob_reqs_in_file;
+    BlobReadContexts& blobs_in_file = ctx.second;
     for (const auto& blob : blobs_in_file) {
+      const BlobIndex& blob_index = blob.first;
       const KeyContext& key_context = blob.second;
-        *(key_context.s) = Status::Corruption("Invalid blob file number");
-      }
-      continue;
-    }
 
-    CacheHandleGuard<BlobFileReader> blob_file_reader;
-    assert(blob_source_);
-    status =
-        blob_source_->GetBlobFileReader(blob_file_number, &blob_file_reader);
-    assert(!status.ok() || blob_file_reader.GetValue());
-
-    auto& blobs_in_file = elem.second;
-    if (!status.ok()) {
-      for (const auto& blob : blobs_in_file) {
-        const KeyContext& key_context = blob.second;
-        *(key_context.s) = status;
-      }
+      if (!blob_file_meta) {
+        *key_context.s = Status::Corruption("Invalid blob file number");
         continue;
       }
 
-    assert(blob_file_reader.GetValue());
-    const uint64_t file_size = blob_file_reader.GetValue()->GetFileSize();
-    const CompressionType compression =
-        blob_file_reader.GetValue()->GetCompressionType();
-
-    // sort blobs_in_file by file offset.
-    std::sort(
-        blobs_in_file.begin(), blobs_in_file.end(),
-        [](const BlobReadRequest& lhs, const BlobReadRequest& rhs) -> bool {
-          assert(lhs.first.file_number() == rhs.first.file_number());
-          return lhs.first.offset() < rhs.first.offset();
-        });
-
-    autovector<std::reference_wrapper<const KeyContext>> blob_read_key_contexts;
-    autovector<std::reference_wrapper<const Slice>> user_keys;
-    autovector<uint64_t> offsets;
-    autovector<uint64_t> value_sizes;
-    autovector<Status*> statuses;
-    autovector<PinnableSlice*> values;
-    for (const auto& blob : blobs_in_file) {
-      const auto& blob_index = blob.first;
-      const KeyContext& key_context = blob.second;
       if (blob_index.HasTTL() || blob_index.IsInlined()) {
-        *(key_context.s) =
+        *key_context.s =
             Status::Corruption("Unexpected TTL/inlined blob index");
         continue;
       }
-      const uint64_t key_size = key_context.ukey_with_ts.size();
-      const uint64_t offset = blob_index.offset();
-      const uint64_t value_size = blob_index.size();
-      if (!IsValidBlobOffset(offset, key_size, value_size, file_size)) {
-        *(key_context.s) = Status::Corruption("Invalid blob offset");
-        continue;
+
+      key_context.value->Reset();
+      blob_reqs_in_file.emplace_back(
+          key_context.ukey_with_ts, blob_index.offset(), blob_index.size(),
+          blob_index.compression(), key_context.value, key_context.s);
+    }
+    if (blob_reqs_in_file.size() > 0) {
+      const auto file_size = blob_file_meta->GetBlobFileSize();
+      blob_reqs.emplace_back(file_number, file_size, blob_reqs_in_file);
     }
-      if (blob_index.compression() != compression) {
-        *(key_context.s) =
-            Status::Corruption("Compression type mismatch when reading a blob");
-        continue;
   }
-      blob_read_key_contexts.emplace_back(std::cref(key_context));
-      user_keys.emplace_back(std::cref(key_context.ukey_with_ts));
-      offsets.push_back(blob_index.offset());
-      value_sizes.push_back(blob_index.size());
-      statuses.push_back(key_context.s);
-      values.push_back(key_context.value);
-    }
-    blob_file_reader.GetValue()->MultiGetBlob(read_options, user_keys, offsets,
-                                              value_sizes, statuses, values,
-                                              /*bytes_read=*/nullptr);
-    size_t num = blob_read_key_contexts.size();
-    assert(num == user_keys.size());
-    assert(num == offsets.size());
-    assert(num == value_sizes.size());
-    assert(num == statuses.size());
-    assert(num == values.size());
-    for (size_t i = 0; i < num; ++i) {
-      if (statuses[i]->ok()) {
-        range.AddValueSize(blob_read_key_contexts[i].get().value->size());
+
+  if (blob_reqs.size() > 0) {
+    blob_source_->MultiGetBlob(read_options, blob_reqs, /*bytes_read=*/nullptr);
+  }
+
+  for (auto& ctx : blob_ctxs) {
+    BlobReadContexts& blobs_in_file = ctx.second;
+    for (const auto& blob : blobs_in_file) {
+      const KeyContext& key_context = blob.second;
+      if (key_context.s->ok()) {
+        range.AddValueSize(key_context.value->size());
         if (range.GetValueSize() > read_options.value_size_soft_limit) {
-          *(blob_read_key_contexts[i].get().s) = Status::Aborted();
+          *key_context.s = Status::Aborted();
         }
+      } else if (key_context.s->IsIncomplete()) {
+        // read_options.read_tier == kBlockCacheTier
+        // Cannot read blob(s): no disk I/O allowed
+        assert(key_context.get_context);
+        auto& get_context = *(key_context.get_context);
+        get_context.MarkKeyMayExist();
       }
     }
   }
@@ -2253,7 +2201,7 @@ void Version::MultiGet(const ReadOptions& read_options, MultiGetRange* range,
 
   MultiGetRange keys_with_blobs_range(*range, range->begin(), range->end());
   // blob_file => [[blob_idx, it], ...]
-  std::unordered_map<uint64_t, BlobReadRequests> blob_rqs;
+  std::unordered_map<uint64_t, BlobReadContexts> blob_ctxs;
   int prev_level = -1;
 
   while (!fp.IsSearchEnded()) {
@@ -2270,7 +2218,7 @@ void Version::MultiGet(const ReadOptions& read_options, MultiGetRange* range,
         // Call MultiGetFromSST for looking up a single file
         s = MultiGetFromSST(read_options, fp.CurrentFileRange(),
                             fp.GetHitFileLevel(), fp.IsHitFileLastInLevel(), f,
-                            blob_rqs, num_filter_read, num_index_read,
+                            blob_ctxs, num_filter_read, num_index_read,
                             num_sst_read);
         if (fp.GetHitFileLevel() == 0) {
           dump_stats_for_l0_file = true;
@@ -2285,7 +2233,7 @@ void Version::MultiGet(const ReadOptions& read_options, MultiGetRange* range,
       while (f != nullptr) {
         mget_tasks.emplace_back(MultiGetFromSSTCoroutine(
             read_options, fp.CurrentFileRange(), fp.GetHitFileLevel(),
-            fp.IsHitFileLastInLevel(), f, blob_rqs, num_filter_read,
+            fp.IsHitFileLastInLevel(), f, blob_ctxs, num_filter_read,
             num_index_read, num_sst_read));
         if (fp.KeyMaySpanNextFile()) {
           break;
@@ -2358,8 +2306,8 @@ void Version::MultiGet(const ReadOptions& read_options, MultiGetRange* range,
                       num_level_read);
   }
 
-  if (s.ok() && !blob_rqs.empty()) {
-    MultiGetBlob(read_options, keys_with_blobs_range, blob_rqs);
+  if (s.ok() && !blob_ctxs.empty()) {
+    MultiGetBlob(read_options, keys_with_blobs_range, blob_ctxs);
   }
 
   // Process any left over keys

db/version_set.h

@@ -860,11 +860,11 @@ class Version {
                  FilePrefetchBuffer* prefetch_buffer, PinnableSlice* value,
                  uint64_t* bytes_read) const;
 
-  using BlobReadRequest =
+  using BlobReadContext =
       std::pair<BlobIndex, std::reference_wrapper<const KeyContext>>;
-  using BlobReadRequests = std::vector<BlobReadRequest>;
+  using BlobReadContexts = std::vector<BlobReadContext>;
   void MultiGetBlob(const ReadOptions& read_options, MultiGetRange& range,
-                    std::unordered_map<uint64_t, BlobReadRequests>& blob_rqs);
+                    std::unordered_map<uint64_t, BlobReadContexts>& blob_ctxs);
 
   // Loads some stats information from files (if update_stats is set) and
   // populates derived data structures. Call without mutex held. It needs to be
@@ -989,7 +989,7 @@ class Version {
       /* ret_type */ Status, /* func_name */ MultiGetFromSST,
       const ReadOptions& read_options, MultiGetRange file_range,
       int hit_file_level, bool is_hit_file_last_in_level, FdWithKeyRange* f,
-      std::unordered_map<uint64_t, BlobReadRequests>& blob_rqs,
+      std::unordered_map<uint64_t, BlobReadContexts>& blob_ctxs,
       uint64_t& num_filter_read, uint64_t& num_index_read,
       uint64_t& num_sst_read);
 

db/version_set_sync_and_async.h

@@ -14,7 +14,7 @@ namespace ROCKSDB_NAMESPACE {
 DEFINE_SYNC_AND_ASYNC(Status, Version::MultiGetFromSST)
 (const ReadOptions& read_options, MultiGetRange file_range, int hit_file_level,
  bool is_hit_file_last_in_level, FdWithKeyRange* f,
- std::unordered_map<uint64_t, BlobReadRequests>& blob_rqs,
+ std::unordered_map<uint64_t, BlobReadContexts>& blob_ctxs,
  uint64_t& num_filter_read, uint64_t& num_index_read, uint64_t& num_sst_read) {
   bool timer_enabled = GetPerfLevel() >= PerfLevel::kEnableTimeExceptForMutex &&
                        get_perf_context()->per_level_perf_context_enabled;
@@ -110,7 +110,7 @@ DEFINE_SYNC_AND_ASYNC(Status, Version::MultiGetFromSST)
             Status tmp_s = blob_index.DecodeFrom(blob_index_slice);
             if (tmp_s.ok()) {
               const uint64_t blob_file_num = blob_index.file_number();
-              blob_rqs[blob_file_num].emplace_back(
+              blob_ctxs[blob_file_num].emplace_back(
                   std::make_pair(blob_index, std::cref(*iter)));
             } else {
               *(iter->s) = tmp_s;