feat(server): Add GETDEL command (#365)

* Added GETDEL command

* fix(server): Implement Del inside OpGet

* fix(server): Swapped result for CHECK macro

* docs(contributors): Added myself to Contributors

CONTRIBUTORS.md

@@ -8,3 +8,4 @@
 * **[Ryan Russell](https://github.com/ryanrussell)**
   * Docs & Code Readability
 * **[Ali-Akber Saifee](https://github.com/alisaifee)**
+* **[Elle Y](https://github.com/inohime)**

src/server/string_family.cc

@@ -191,13 +191,24 @@ OpResult<bool> ExtendOrSkip(const OpArgs& op_args, string_view key, string_view
   return ExtendExisting(op_args, *it_res, key, val, prepend);
 }
 
-OpResult<string> OpGet(const OpArgs& op_args, string_view key) {
+OpResult<string> OpGet(const OpArgs& op_args, string_view key, bool del_hit = false) {
   OpResult<PrimeIterator> it_res = op_args.shard->db_slice().Find(op_args.db_cntx, key, OBJ_STRING);
   if (!it_res.ok())
     return it_res.status();
 
   const PrimeValue& pv = it_res.value()->second;
 
+  if (del_hit) {
+    string key_bearer = GetString(op_args.shard, pv);
+
+    DVLOG(1) << "Del: " << key;
+    auto& db_slice = op_args.shard->db_slice();
+
+    CHECK(db_slice.Del(op_args.db_cntx.db_index, it_res.value()));
+
+    return key_bearer;
+  }
+
   return GetString(op_args.shard, pv);
 }
 
@@ -597,6 +608,36 @@ void StringFamily::Get(CmdArgList args, ConnectionContext* cntx) {
   }
 }
 
+void StringFamily::GetDel(CmdArgList args, ConnectionContext* cntx) {
+  get_qps.Inc();
+
+  string_view key = ArgS(args, 1);
+
+  auto cb = [&](Transaction* t, EngineShard* shard) {
+    bool run_del = true;
+    return OpGet(t->GetOpArgs(shard), key, run_del);
+  };
+
+  DVLOG(1) << "Before Get::ScheduleSingleHopT " << key;
+
+  Transaction* trans = cntx->transaction;
+  OpResult<string> result = trans->ScheduleSingleHopT(std::move(cb));
+
+  if (result) {
+    DVLOG(1) << "GET " << trans->DebugId() << ": " << key << " " << result.value();
+    (*cntx)->SendBulkString(*result);
+  } else {
+    switch (result.status()) {
+      case OpStatus::WRONG_TYPE:
+        (*cntx)->SendError(kWrongTypeErr);
+        break;
+      default:
+        DVLOG(1) << "GET " << key << " nil";
+        (*cntx)->SendNull();
+    }
+  }
+}
+
 void StringFamily::GetSet(CmdArgList args, ConnectionContext* cntx) {
   string_view key = ArgS(args, 1);
   string_view value = ArgS(args, 2);
@@ -1038,6 +1079,7 @@ void StringFamily::Register(CommandRegistry* registry) {
             << CI{"INCRBYFLOAT", CO::WRITE | CO::DENYOOM | CO::FAST, 3, 1, 1, 1}.HFUNC(IncrByFloat)
             << CI{"DECRBY", CO::WRITE | CO::DENYOOM | CO::FAST, 3, 1, 1, 1}.HFUNC(DecrBy)
             << CI{"GET", CO::READONLY | CO::FAST, 2, 1, 1, 1}.HFUNC(Get)
+            << CI{"GETDEL", CO::WRITE | CO::DENYOOM | CO::FAST, 2, 1, 1, 1}.HFUNC(GetDel)
             << CI{"GETSET", CO::WRITE | CO::DENYOOM | CO::FAST, 3, 1, 1, 1}.HFUNC(GetSet)
             << CI{"MGET", CO::READONLY | CO::FAST | CO::REVERSE_MAPPING, -2, 1, -1, 1}.HFUNC(MGet)
             << CI{"MSET", CO::WRITE | CO::DENYOOM, -3, 1, -1, 2}.HFUNC(MSet)

src/server/string_family.h

@@ -57,6 +57,7 @@ class StringFamily {
   static void Decr(CmdArgList args, ConnectionContext* cntx);
   static void DecrBy(CmdArgList args, ConnectionContext* cntx);
   static void Get(CmdArgList args, ConnectionContext* cntx);
+  static void GetDel(CmdArgList args, ConnectionContext* cntx);
   static void GetRange(CmdArgList args, ConnectionContext* cntx);
   static void GetSet(CmdArgList args, ConnectionContext* cntx);
   static void Incr(CmdArgList args, ConnectionContext* cntx);

src/server/string_family_test.cc

@@ -387,4 +387,16 @@ TEST_F(StringFamilyTest, SetPxAtExAt) {
   EXPECT_EQ(Run({"get", "foo2"}), "abc");
 }
 
+TEST_F(StringFamilyTest, GetDel) {
+  auto resp = Run({"set", "foo", "bar"});
+  EXPECT_THAT(resp, "OK");
+
+  resp = Run({"getdel", "foo"});
+  // foo's value
+  ASSERT_THAT(resp, ArgType(RespExpr::STRING));
+
+  resp = Run({"get", "foo"});
+  ASSERT_THAT(resp, ArgType(RespExpr::NIL));
+}
+
 }  // namespace dfly