[incubator-kvrocks] branch unstable updated: Use the rocksdb mget to improve the performance (#1453)

[hu...@apache.org]

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hulk pushed a commit to branch unstable
in repository https://gitbox.apache.org/repos/asf/incubator-kvrocks.git


The following commit(s) were added to refs/heads/unstable by this push:
     new 60d13ef9 Use the rocksdb mget to improve the performance (#1453)
60d13ef9 is described below

commit 60d13ef9c71a401b59a011f686a1b8e6024360e4
Author: Zevin <ze...@gmail.com>
AuthorDate: Mon May 22 13:27:41 2023 +0800

    Use the rocksdb mget to improve the performance (#1453)
    
    DB::MultiGet pushes fields query to RocksDB, thus RocksDB can perform optimizations, such as async io by io uring.
    Although this optimization is less than mget for strings, it is valuable
    because different fields may lies in different levels of the LSM Tree, thus async io can take effect.
---
 src/types/redis_hash.cc | 25 ++++++++++++++++++-------
 1 file changed, 18 insertions(+), 7 deletions(-)

diff --git a/src/types/redis_hash.cc b/src/types/redis_hash.cc
index 389b8e19..8cec66ad 100644
--- a/src/types/redis_hash.cc
+++ b/src/types/redis_hash.cc
@@ -174,16 +174,27 @@ rocksdb::Status Hash::MGet(const Slice &user_key, const std::vector<Slice> &fiel
   rocksdb::ReadOptions read_options;
   read_options.snapshot = ss.GetSnapShot();
   storage_->SetReadOptions(read_options);
+  std::vector<rocksdb::Slice> keys;
 
-  std::string sub_key, value;
+  keys.reserve(fields.size());
+  std::vector<std::string> sub_keys;
+  sub_keys.resize(fields.size());
+  int i = 0;
   for (const auto &field : fields) {
-    InternalKey(ns_key, field, metadata.version, storage_->IsSlotIdEncoded()).Encode(&sub_key);
-    value.clear();
-    s = storage_->Get(read_options, sub_key, &value);
-    if (!s.ok() && !s.IsNotFound()) return s;
+    InternalKey(ns_key, field, metadata.version, storage_->IsSlotIdEncoded()).Encode(&(sub_keys[i]));
+    keys.emplace_back(sub_keys[i++]);
+  }
 
-    values->emplace_back(value);
-    statuses->emplace_back(s);
+  std::vector<rocksdb::PinnableSlice> values_vector;
+  values_vector.resize(keys.size());
+  std::vector<rocksdb::Status> statuses_vector;
+  statuses_vector.resize(keys.size());
+  storage_->MultiGet(read_options, storage_->GetDB()->DefaultColumnFamily(), keys.size(), keys.data(),
+                     values_vector.data(), statuses_vector.data());
+  for (size_t i = 0; i < keys.size(); i++) {
+    if (!statuses_vector[i].ok() && !statuses_vector[i].IsNotFound()) return statuses_vector[i];
+    values->emplace_back(values_vector[i].ToString());
+    statuses->emplace_back(statuses_vector[i]);
   }
   return rocksdb::Status::OK();
 }