Implement HCLONE for copying entire hashes

CHANGELOG.md

 # Changelog
 All notable changes to this project will be documented in this file.
 
+## Unreleased
+### Added
+- Command `hclone` for creating identical copies of entire hashes.
+
 ## 0.2.9 (2018-07-16)
 ### Added
 - Commands `convert-string-to-int`, `convert-int-to-string` to convert between

src/Commands.cc

@@ -75,6 +75,7 @@ struct cmdMapInit {
     redis_cmd_map["hincrbyfloat"] = {RedisCommand::HINCRBYFLOAT, CommandType::WRITE};
     redis_cmd_map["hincrbymulti"] = {RedisCommand::HINCRBYMULTI, CommandType::WRITE};
     redis_cmd_map["hdel"] = {RedisCommand::HDEL, CommandType::WRITE};
+    redis_cmd_map["hclone"] = {RedisCommand::HCLONE, CommandType::WRITE};
     redis_cmd_map["sadd"] = {RedisCommand::SADD, CommandType::WRITE};
     redis_cmd_map["srem"] = {RedisCommand::SREM, CommandType::WRITE};
     redis_cmd_map["smove"] = {RedisCommand::SMOVE, CommandType::WRITE};

src/Commands.hh

@@ -63,6 +63,7 @@ enum class RedisCommand {
   HSCAN,
   HSETNX,
   HINCRBYFLOAT,
+  HCLONE,
 
   LHMSET,
   LHSET,

src/Dispatcher.cc

@@ -235,6 +235,13 @@ RedisEncodedResponse RedisDispatcher::dispatchWrite(StagingArea &stagingArea, Re
       if(request.size() <= 2) return errArgs(request);
       return dispatchHDEL(stagingArea, request[1], request.begin()+2, request.end());
     }
+    case RedisCommand::HCLONE: {
+      if(request.size() != 3) return errArgs(request);
+
+      rocksdb::Status st = store.hclone(stagingArea, request[1], request[2]);
+      if(!st.ok()) return Formatter::fromStatus(st);
+      return Formatter::ok();
+    }
     case RedisCommand::SADD: {
       if(request.size() <= 2) return errArgs(request);
       int64_t count = 0;

src/StateMachine.cc

@@ -1098,6 +1098,44 @@ rocksdb::Status StateMachine::lease_get(StagingArea &stagingArea, const std::str
   return rocksdb::Status::OK();
 }
 
+rocksdb::Status StateMachine::hclone(StagingArea &stagingArea, const std::string &source, const std::string &target) {
+  WriteOperation operation(stagingArea, target, KeyType::kHash);
+  if(!operation.valid()) return wrong_type();
+  if(operation.keyExists()) {
+    operation.cancel();
+    return rocksdb::Status::InvalidArgument("ERR target key already exists, will not overwrite");
+  }
+
+  KeyDescriptor sourceKeyInfo = getKeyDescriptor(stagingArea, source);
+  if(sourceKeyInfo.empty()) {
+    operation.cancel();
+    return rocksdb::Status::OK(); // source key is empty, do nothing
+  }
+
+  if(sourceKeyInfo.getKeyType() != KeyType::kHash) {
+    operation.cancel();
+    return wrong_type();
+  }
+
+  int64_t newsize = 0;
+  FieldLocator locator(KeyType::kHash, source);
+
+  IteratorPtr iter(stagingArea.getIterator());
+  for(iter->Seek(locator.getPrefix()); iter->Valid(); iter->Next()) {
+    std::string tmp = iter->key().ToString();
+    if(!StringUtils::startswith(tmp, locator.toSlice())) break;
+
+    operation.writeField(
+      std::string(tmp.begin()+locator.getPrefixSize(), tmp.end()),
+      iter->value().ToString()
+    );
+    newsize++;
+  }
+
+  qdb_assert(newsize == sourceKeyInfo.getSize());
+  return operation.finalize(newsize);
+}
+
 void StateMachine::advanceClock(ClockValue newValue, LogIndex index) {
   StagingArea stagingArea(*this);
   advanceClock(stagingArea, newValue);

src/StateMachine.hh

@@ -73,6 +73,7 @@ public:
   rocksdb::Status hincrby(StagingArea &stagingArea, const std::string &key, const std::string &field, const std::string &incrby, int64_t &result);
   rocksdb::Status hincrbyfloat(StagingArea &stagingArea, const std::string &key, const std::string &field, const std::string &incrby, double &result);
   rocksdb::Status hdel(StagingArea &stagingArea, const std::string &key, const VecIterator &start, const VecIterator &end, int64_t &removed);
+  rocksdb::Status hclone(StagingArea &stagingArea, const std::string &source, const std::string &target);
 
   rocksdb::Status lhset(StagingArea &stagingArea, const std::string &key, const std::string &field, const std::string &hint, const std::string &value, bool &fieldcreated);
   rocksdb::Status lhdel(StagingArea &stagingArea, const std::string &key, const VecIterator &start, const VecIterator &end, int64_t &removed);

test/e2e.cc

@@ -1354,3 +1354,56 @@ TEST_F(Raft_e2e, InconsistentIteratorsTest) {
 
   ASSERT_REPLY(delReply, 1);
 }
+
+TEST_F(Raft_e2e, CloneHash) {
+  spinup(0); spinup(1); spinup(2);
+  RETRY_ASSERT_TRUE(checkStateConsensus(0, 1, 2));
+
+  int leaderID = getLeaderID();
+
+  std::vector<std::future<redisReplyPtr>> replies;
+  for(size_t i = 0; i < 10; i++) {
+    replies.emplace_back(tunnel(leaderID)->exec("HSET", "hash", SSTR("f" << i), SSTR("v" << i)));
+  }
+
+  for(size_t i = 0; i < 10; i++) {
+    ASSERT_REPLY(replies[i], 1);
+  }
+
+  ASSERT_REPLY(tunnel(leaderID)->exec("hclone", "hash", "hash2"), "OK");
+
+  redisReplyPtr hgetall = tunnel(leaderID)->exec("hgetall", "hash2").get();
+
+  ASSERT_EQ(
+    qclient::describeRedisReply(hgetall),
+    "1) \"f0\"\n"
+    "2) \"v0\"\n"
+    "3) \"f1\"\n"
+    "4) \"v1\"\n"
+    "5) \"f2\"\n"
+    "6) \"v2\"\n"
+    "7) \"f3\"\n"
+    "8) \"v3\"\n"
+    "9) \"f4\"\n"
+    "10) \"v4\"\n"
+    "11) \"f5\"\n"
+    "12) \"v5\"\n"
+    "13) \"f6\"\n"
+    "14) \"v6\"\n"
+    "15) \"f7\"\n"
+    "16) \"v7\"\n"
+    "17) \"f8\"\n"
+    "18) \"v8\"\n"
+    "19) \"f9\"\n"
+    "20) \"v9\"\n"
+  );
+
+  ASSERT_REPLY(tunnel(leaderID)->exec("hclone", "hash", "hash2"), "ERR Invalid argument: ERR target key already exists, will not overwrite");
+  ASSERT_REPLY(tunnel(leaderID)->exec("sadd", "my-set", "s1"), 1);
+
+  ASSERT_REPLY(tunnel(leaderID)->exec("hclone", "my-set", "hash3"), "ERR Invalid argument: WRONGTYPE Operation against a key holding the wrong kind of value");
+  ASSERT_REPLY(tunnel(leaderID)->exec("hclone", "hash", "my-set"), "ERR Invalid argument: WRONGTYPE Operation against a key holding the wrong kind of value");
+  ASSERT_REPLY(tunnel(leaderID)->exec("hclone", "not-existing", "hash"), "ERR Invalid argument: ERR target key already exists, will not overwrite");
+  ASSERT_REPLY(tunnel(leaderID)->exec("hclone", "not-existing", "not-existing-2"), "OK");
+  ASSERT_REPLY(tunnel(leaderID)->exec("exists", "not-existing", "not-existing-2"), 0);
+}