chore: get rid of kv_args and replace it with slices to full_args

The main change is in tx_base.* where we introduce ShardArgs slice that
is only forward iterable. It allows us to go over sub-ranges of the full arguments
slice or read an index of any of its elements.

Since ShardArgs provide now indices into the original argument list we do not need to build the reverse index in transactions.

Signed-off-by: Roman Gershman <[email protected]>

src/server/command_registry.cc

@@ -40,9 +40,6 @@ CommandId::CommandId(const char* name, uint32_t mask, int8_t arity, int8_t first
  : facade::CommandId(name, mask, arity, first_key, last_key, acl_categories) {
  if (mask & CO::ADMIN)
  opt_mask_ |= CO::NOSCRIPT;
-
- if (mask & CO::BLOCKING)
- opt_mask_ |= CO::REVERSE_MAPPING;
 }
 
 bool CommandId::IsTransactional() const {
@@ -173,8 +170,6 @@ const char* OptName(CO::CommandOpt fl) {
  return "readonly";
  case DENYOOM:
  return "denyoom";
- case REVERSE_MAPPING:
- return "reverse-mapping";
  case FAST:
  return "fast";
  case LOADING:

src/server/command_registry.h

@@ -27,16 +27,13 @@ enum CommandOpt : uint32_t {
  LOADING = 1U << 3, // Command allowed during LOADING state.
  DENYOOM = 1U << 4, // use-memory in redis.
 
- // marked commands that demand preserve the order of keys to work correctly.
- // For example, MGET needs to know the order of keys to return the values in the same order.
- // BLPOP needs to know the order of keys to return the first non-empty list from the left.
- REVERSE_MAPPING = 1U << 5,
+ // UNUSED = 1U << 5,
 
  VARIADIC_KEYS = 1U << 6, // arg 2 determines number of keys. Relevant for ZUNIONSTORE, EVAL etc.
 
  ADMIN = 1U << 7, // implies NOSCRIPT,
  NOSCRIPT = 1U << 8,
- BLOCKING = 1U << 9, // implies REVERSE_MAPPING
+ BLOCKING = 1U << 9,
  HIDDEN = 1U << 10, // does not show in COMMAND command output
  INTERLEAVED_KEYS = 1U << 11, // keys are interleaved with arguments
  GLOBAL_TRANS = 1U << 12,

src/server/container_utils.cc

@@ -40,14 +40,12 @@ OpResult<std::pair<DbSlice::ConstIterator, unsigned>> FindFirstReadOnly(const Db
  int req_obj_type) {
  DCHECK(!args.Empty());
 
- unsigned i = 0;
- for (string_view key : args) {
- OpResult<DbSlice::ConstIterator> res = db_slice.FindReadOnly(cntx, key, req_obj_type);
+ for (auto it = args.begin(); it != args.end(); ++it) {
+ OpResult<DbSlice::ConstIterator> res = db_slice.FindReadOnly(cntx, *it, req_obj_type);
  if (res)
- return make_pair(res.value(), i);
+ return make_pair(res.value(), unsigned(it.index()));
  if (res.status() != OpStatus::KEY_NOTFOUND)
  return res.status();
- ++i;
  }
 
  VLOG(2) << "FindFirst not found";
@@ -119,8 +117,8 @@ OpResult<ShardFFResult> FindFirstNonEmpty(Transaction* trans, int req_obj_type)
  auto comp = [trans](const OpResult<FFResult>& lhs, const OpResult<FFResult>& rhs) {
  if (!lhs || !rhs)
  return lhs.ok();
- size_t i1 = trans->ReverseArgIndex(std::get<ShardId>(*lhs), std::get<unsigned>(*lhs));
- size_t i2 = trans->ReverseArgIndex(std::get<ShardId>(*rhs), std::get<unsigned>(*rhs));
+ size_t i1 = std::get<1>(*lhs);
+ size_t i2 = std::get<1>(*rhs);
  return i1 < i2;
  };
 

src/server/journal/types.h

@@ -42,15 +42,17 @@ struct Entry : public EntryBase {
  struct Payload {
  std::string_view cmd;
  std::variant<CmdArgList, // Parts of a full command.
- ShardArgs  // Command and its shard parts.
- >
+ ShardArgs, // Shard parts.
+ ArgSlice>
  args;
 
  Payload() = default;
  Payload(std::string_view c, CmdArgList a) : cmd(c), args(a) {
  }
  Payload(std::string_view c, const ShardArgs& a) : cmd(c), args(a) {
  }
+ Payload(std::string_view c, ArgSlice a) : cmd(c), args(a) {
+ }
  };
 
  Entry(TxId txid, Op opcode, DbIndex dbid, uint32_t shard_cnt,

src/server/json_family.cc

@@ -1543,12 +1543,14 @@ void JsonFamily::MGet(CmdArgList args, ConnectionContext* cntx) {
  continue;
 
  vector<OptString>& res = mget_resp[sid];
- for (size_t j = 0; j < res.size(); ++j) {
- if (!res[j])
+ ShardArgs shard_args = transaction->GetShardArgs(sid);
+ unsigned src_index = 0;
+ for (auto it = shard_args.begin(); it != shard_args.end(); ++it, ++src_index) {
+ if (!res[src_index])
  continue;
 
- uint32_t indx = transaction->ReverseArgIndex(sid, j);
- results[indx] = std::move(res[j]);
+ uint32_t dst_indx = it.index();
+ results[dst_indx] = std::move(res[src_index]);
  }
  }
 
@@ -2091,8 +2093,7 @@ void JsonFamily::Register(CommandRegistry* registry) {
  constexpr size_t kMsetFlags = CO::WRITE | CO::DENYOOM | CO::FAST | CO::INTERLEAVED_KEYS;
  registry->StartFamily();
  *registry << CI{"JSON.GET", CO::READONLY | CO::FAST, -2, 1, 1, acl::JSON}.HFUNC(Get);
- *registry << CI{"JSON.MGET", CO::READONLY | CO::FAST | CO::REVERSE_MAPPING, -3, 1, -2, acl::JSON}
- .HFUNC(MGet);
+ *registry << CI{"JSON.MGET", CO::READONLY | CO::FAST, -3, 1, -2, acl::JSON}.HFUNC(MGet);
  *registry << CI{"JSON.TYPE", CO::READONLY | CO::FAST, 3, 1, 1, acl::JSON}.HFUNC(Type);
  *registry << CI{"JSON.STRLEN", CO::READONLY | CO::FAST, 3, 1, 1, acl::JSON}.HFUNC(StrLen);
  *registry << CI{"JSON.OBJLEN", CO::READONLY | CO::FAST, 3, 1, 1, acl::JSON}.HFUNC(ObjLen);

src/server/list_family.cc

@@ -158,6 +158,22 @@ struct CircularMessages {
 // Used to recover logs for BLPOP failures. See OpBPop.
 thread_local CircularMessages debugMessages{50};
 
+// A bit awkward translation from a single key to ShardArgs.
+// We create a mutable slice (which will never be mutated) from the key, then we create
+// a CmdArgList of size 1 that references mslice and finally
+// we reference the first element in the CmdArgList via islice.
+struct SingleArg {
+ MutableSlice mslice;
+ IndexSlice islice{0, 1};
+
+ SingleArg(string_view arg) : mslice(const_cast<char*>(arg.data()), arg.size()) {
+ }
+
+ ShardArgs Get() {
+ return ShardArgs{CmdArgList{&mslice, 1}, absl::MakeSpan(&islice, 1)};
+ }
+};
+
 class BPopPusher {
  public:
  BPopPusher(string_view pop_key, string_view push_key, ListDir popdir, ListDir pushdir);
@@ -448,7 +464,9 @@ OpResult<string> MoveTwoShards(Transaction* trans, string_view src, string_view
  // hack, again. since we hacked which queue we are waiting on (see RunPair)
  // we must clean-up src key here manually. See RunPair why we do this.
  // in short- we suspended on "src" on both shards.
- shard->blocking_controller()->FinalizeWatched(ArgSlice{&src, 1}, t);
+
+ SingleArg single_arg{src};
+ shard->blocking_controller()->FinalizeWatched(single_arg.Get(), t);
  }
  } else {
  DVLOG(1) << "Popping value from list: " << key;
@@ -873,7 +891,8 @@ OpResult<string> BPopPusher::RunSingle(ConnectionContext* cntx, time_point tp) {
  return op_res;
  }
 
- auto wcb = [&](Transaction* t, EngineShard* shard) { return ShardArgs{&this->pop_key_, 1}; };
+ SingleArg single_arg{pop_key_};
+ auto wcb = [&](Transaction* t, EngineShard* shard) { return single_arg.Get(); };
 
  const auto key_checker = [](EngineShard* owner, const DbContext& context, Transaction*,
  std::string_view key) -> bool {
@@ -900,11 +919,13 @@ OpResult<string> BPopPusher::RunPair(ConnectionContext* cntx, time_point tp) {
  return op_res;
  }
 
+ SingleArg single_arg(this->pop_key_);
+
  // a hack: we watch in both shards for pop_key but only in the source shard it's relevant.
  // Therefore we follow the regular flow of watching the key but for the destination shard it
  // will never be triggerred.
  // This allows us to run Transaction::Execute on watched transactions in both shards.
- auto wcb = [&](Transaction* t, EngineShard* shard) { return ArgSlice{&this->pop_key_, 1}; };
+ auto wcb = [&](Transaction* t, EngineShard* shard) { return single_arg.Get(); };
 
  const auto key_checker = [](EngineShard* owner, const DbContext& context, Transaction*,
  std::string_view key) -> bool {

src/server/stream_family.cc

@@ -2989,17 +2989,19 @@ void XReadImpl(CmdArgList args, std::optional<ReadOpts> opts, ConnectionContext*
  continue;
 
  vector<RecordVec>& results = xread_resp[sid];
+ unsigned src_index = 0;
+ ShardArgs shard_args = cntx->transaction->GetShardArgs(sid);
 
- for (size_t i = 0; i < results.size(); ++i) {
- if (results[i].size() == 0) {
+ for (auto it = shard_args.begin(); it != shard_args.end(); ++it, ++src_index) {
+ if (results[src_index].size() == 0) {
  continue;
  }
 
  resolved_streams++;
 
  // Add the stream records ordered by the original stream arguments.
- size_t indx = cntx->transaction->ReverseArgIndex(sid, i);
- res[indx - opts->streams_arg] = std::move(results[i]);
+ size_t dst_indx = it.index();
+ res[dst_indx - opts->streams_arg] = std::move(results[src_index]);
  }
  }
 
@@ -3323,7 +3325,7 @@ constexpr uint32_t kXAutoClaim = WRITE | STREAM | FAST;
 void StreamFamily::Register(CommandRegistry* registry) {
  using CI = CommandId;
  registry->StartFamily();
- constexpr auto kReadFlags = CO::READONLY | CO::BLOCKING | CO::REVERSE_MAPPING | CO::VARIADIC_KEYS;
+ constexpr auto kReadFlags = CO::READONLY | CO::BLOCKING | CO::VARIADIC_KEYS;
  *registry << CI{"XADD", CO::WRITE | CO::DENYOOM | CO::FAST, -5, 1, 1, acl::kXAdd}.HFUNC(XAdd)
  << CI{"XCLAIM", CO::WRITE | CO::FAST, -6, 1, 1, acl::kXClaim}.HFUNC(XClaim)
  << CI{"XDEL", CO::WRITE | CO::FAST, -3, 1, 1, acl::kXDel}.HFUNC(XDel)

src/server/string_family.cc

@@ -275,13 +275,15 @@ void OpMSet(const OpArgs& op_args, const ShardArgs& args, atomic_bool* success)
  SetCmd sg(op_args, false);
 
  size_t index = 0;
+ bool partial = false;
  for (auto it = args.begin(); it != args.end(); ++it) {
  string_view key = *it;
  ++it;
  string_view value = *it;
  DVLOG(1) << "MSet " << key << ":" << value;
  if (sg.Set(params, key, value) != OpStatus::OK) { // OOM for example.
  success->store(false);
+ partial = true;
  break;
  }
  index += 2;
@@ -290,18 +292,29 @@ void OpMSet(const OpArgs& op_args, const ShardArgs& args, atomic_bool* success)
  if (auto journal = op_args.shard->journal(); journal) {
  // We write a custom journal because an OOM in the above loop could lead to partial success, so
  // we replicate only what was changed.
- string_view cmd;
- ArgSlice cmd_args;
- if (index == 0) {
- // All shards must record the tx was executed for the replica to execute it, so we send a PING
- // in case nothing was changed
- cmd = "PING";
+ if (partial) {
+ string_view cmd;
+ ArgSlice cmd_args;
+ vector<string_view> store_args(index);
+ if (index == 0) {
+ // All shards must record the tx was executed for the replica to execute it, so we send a
+ // PING in case nothing was changed
+ cmd = "PING";
+ } else {
+ // journal [0, i)
+ cmd = "MSET";
+ unsigned i = 0;
+ for (string_view arg : args) {
+ store_args[i++] = arg;
+ if (i >= store_args.size())
+ break;
+ }
+ cmd_args = absl::MakeSpan(store_args);
+ }
+ RecordJournal(op_args, cmd, cmd_args, op_args.tx->GetUniqueShardCnt());
  } else {
- // journal [0, i)
- cmd = "MSET";
- cmd_args = ArgSlice(args.begin(), index);
+ RecordJournal(op_args, "MSET", args, op_args.tx->GetUniqueShardCnt());
  }
- RecordJournal(op_args, cmd, cmd_args, op_args.tx->GetUniqueShardCnt());
  }
 }
 
@@ -1163,16 +1176,17 @@ void StringFamily::MGet(CmdArgList args, ConnectionContext* cntx) {
  src.storage_list->next = res.storage_list;
  res.storage_list = src.storage_list;
  src.storage_list = nullptr;
-
- for (size_t j = 0; j < src.resp_arr.size(); ++j) {
- if (!src.resp_arr[j])
+ ShardArgs shard_args = transaction->GetShardArgs(sid);
+ unsigned src_indx = 0;
+ for (auto it = shard_args.begin(); it != shard_args.end(); ++it, ++src_indx) {
+ if (!src.resp_arr[src_indx])
  continue;
 
- uint32_t indx = transaction->ReverseArgIndex(sid, j);
+ uint32_t indx = it.index();
 
- res.resp_arr[indx] = std::move(src.resp_arr[j]);
+ res.resp_arr[indx] = std::move(src.resp_arr[src_indx]);
  if (cntx->protocol() == Protocol::MEMCACHE) {
- res.resp_arr[indx]->key = ArgS(args, indx);
+ res.resp_arr[indx]->key = *it;
  }
  }
  }
@@ -1488,9 +1502,7 @@ void StringFamily::Register(CommandRegistry* registry) {
  << CI{"GETEX", CO::WRITE | CO::DENYOOM | CO::FAST | CO::NO_AUTOJOURNAL, -1, 1, 1, acl::kGetEx}
  .HFUNC(GetEx)
  << CI{"GETSET", CO::WRITE | CO::DENYOOM | CO::FAST, 3, 1, 1, acl::kGetSet}.HFUNC(GetSet)
- << CI{"MGET", CO::READONLY | CO::FAST | CO::REVERSE_MAPPING | CO::IDEMPOTENT, -2, 1, -1,
- acl::kMGet}
- .HFUNC(MGet)
+ << CI{"MGET", CO::READONLY | CO::FAST | CO::IDEMPOTENT, -2, 1, -1, acl::kMGet}.HFUNC(MGet)
  << CI{"MSET", kMSetMask, -3, 1, -1, acl::kMSet}.HFUNC(MSet)
  << CI{"MSETNX", kMSetMask, -3, 1, -1, acl::kMSetNx}.HFUNC(MSetNx)
  << CI{"STRLEN", CO::READONLY | CO::FAST, 2, 1, 1, acl::kStrLen}.HFUNC(StrLen)