Implement deque trimming method, only in state machine for now

qclient @ b71d76c0

-Subproject commit 7e410bd8fc4d1a6e5f782792209f2e6d24e0d06a
+Subproject commit b71d76c06850b45a86758e3ac6d1052364ded3b6

src/Commands.cc

@@ -83,6 +83,7 @@ struct cmdMapInit {
     redis_cmd_map["deque_pop_front"] = {RedisCommand::DEQUE_POP_FRONT, CommandType::WRITE};
     redis_cmd_map["deque_push_back"] = {RedisCommand::DEQUE_PUSH_BACK, CommandType::WRITE};
     redis_cmd_map["deque_pop_back"] = {RedisCommand::DEQUE_POP_BACK, CommandType::WRITE};
+    redis_cmd_map["deque_trim_front"] = {RedisCommand::DEQUE_TRIM_FRONT, CommandType::WRITE};
     redis_cmd_map["config_set"] = {RedisCommand::CONFIG_SET, CommandType::WRITE};
     redis_cmd_map["lhset"] = {RedisCommand::LHSET, CommandType::WRITE};
     redis_cmd_map["lhdel"] = {RedisCommand::LHDEL, CommandType::WRITE};

src/Commands.hh

@@ -88,6 +88,7 @@ enum class RedisCommand {
   DEQUE_POP_FRONT,
   DEQUE_PUSH_BACK,
   DEQUE_POP_BACK,
+  DEQUE_TRIM_FRONT,
   DEQUE_LEN,
 
   RAW_SCAN,

src/StateMachine.cc

@@ -1055,6 +1055,31 @@ rocksdb::Status StateMachine::dequePopBack(StagingArea &stagingArea, const std::
   return this->dequePop(stagingArea, Direction::kRight, key, item);
 }
 
+rocksdb::Status StateMachine::dequeTrimFront(StagingArea &stagingArea, const std::string &key, uint64_t maxToKeep, int64_t &itemsRemoved) {
+  WriteOperation operation(stagingArea, key, KeyType::kDeque);
+  if(!operation.valid()) return wrong_type();
+
+  KeyDescriptor &descriptor = operation.descriptor();
+
+  int64_t toRemove = descriptor.getSize() - maxToKeep;
+  if(toRemove <= 0) {
+    operation.cancel();
+    itemsRemoved = 0;
+    return rocksdb::Status::OK();
+  }
+
+  for(uint64_t nextToEliminate = descriptor.getStartIndex()+1; nextToEliminate <=
+    descriptor.getStartIndex() + toRemove; nextToEliminate++) {
+    qdb_assert(operation.deleteField(unsignedIntToBinaryString(nextToEliminate)));
+  }
+
+  itemsRemoved = toRemove;
+  descriptor.setStartIndex(descriptor.getStartIndex() + toRemove);
+
+  qdb_assert(descriptor.getEndIndex() - descriptor.getStartIndex() - 1 == maxToKeep);
+  return operation.finalize(descriptor.getEndIndex() - descriptor.getStartIndex() - 1);
+}
+
 void StateMachine::advanceClock(StagingArea &stagingArea, ClockValue newValue) {
   // Assert we're not setting the clock back..
   ClockValue prevValue;
@@ -1780,3 +1805,7 @@ rocksdb::Status StateMachine::lease_get(const std::string &key, ClockValue clock
 rocksdb::Status StateMachine::lease_release(const std::string &key, ClockValue clockUpdate,  LogIndex index) {
   CHAIN(index, lease_release, key, clockUpdate);
 }
+
+rocksdb::Status StateMachine::dequeTrimFront(const std::string &key, uint64_t maxToKeep, int64_t &itemsRemoved, LogIndex index) {
+  CHAIN(index, dequeTrimFront, key, maxToKeep, itemsRemoved);
+}
\ No newline at end of file

src/StateMachine.hh

@@ -87,6 +87,7 @@ public:
   rocksdb::Status dequePushBack(StagingArea &stagingArea, const std::string &key, const VecIterator &start, const VecIterator &end, int64_t &length);
   rocksdb::Status dequePopFront(StagingArea &stagingArea, const std::string &key, std::string &item);
   rocksdb::Status dequePopBack(StagingArea &stagingArea, const std::string &key, std::string &item);
+  rocksdb::Status dequeTrimFront(StagingArea &stagingArea, const std::string &key, uint64_t maxToKeep, int64_t &itemsRemoved);
 
   void advanceClock(StagingArea &stagingArea, ClockValue newValue);
   LeaseAcquisitionStatus lease_acquire(StagingArea &stagingArea, const std::string &key, const std::string &value, ClockValue clockUpdate, uint64_t duration, LeaseInfo &info);
@@ -150,6 +151,7 @@ public:
   rocksdb::Status dequePushBack(const std::string &key, const VecIterator &start, const VecIterator &end, int64_t &length, LogIndex index = 0);
   rocksdb::Status dequePopFront(const std::string &key, std::string &item, LogIndex index = 0);
   rocksdb::Status dequePopBack(const std::string &key, std::string &item, LogIndex index = 0);
+  rocksdb::Status dequeTrimFront(const std::string &key, uint64_t maxToKeep, int64_t &itemsRemoved, LogIndex index = 0);
   rocksdb::Status dequeLen(const std::string &key, size_t &len);
   rocksdb::Status lhset(const std::string &key, const std::string &field, const std::string &hint, const std::string &value, bool &fieldcreated, LogIndex index = 0);
   rocksdb::Status lhlen(const std::string &key, size_t &len);

test/state-machine.cc

@@ -402,6 +402,45 @@ TEST_F(State_Machine, DequeOperations) {
   ASSERT_NOTFOUND(stateMachine()->dequePopFront("my_list", item));
 }
 
+TEST_F(State_Machine, DequeTrimming) {
+  std::vector<std::string> vec = {"1", "2", "3", "4", "5", "6", "7"};
+  int64_t length;
+
+  ASSERT_OK(stateMachine()->dequePushBack("my-deque", vec.begin(), vec.end(), length));
+  ASSERT_EQ(length, 7);
+
+  ASSERT_OK(stateMachine()->dequeTrimFront("my-deque", 50, length));
+  ASSERT_EQ(length, 0);
+
+  size_t len;
+  ASSERT_OK(stateMachine()->dequeLen("my-deque", len));
+  ASSERT_EQ(len, 7u);
+
+  ASSERT_OK(stateMachine()->dequeTrimFront("my-deque", 5, length));
+  ASSERT_EQ(length, 2);
+
+  ASSERT_OK(stateMachine()->dequeLen("my-deque", len));
+  ASSERT_EQ(len, 5u);
+
+  std::string item;
+  ASSERT_OK(stateMachine()->dequePopFront("my-deque", item));
+  ASSERT_EQ(item, "3");
+
+  ASSERT_OK(stateMachine()->dequePopFront("my-deque", item));
+  ASSERT_EQ(item, "4");
+
+  ASSERT_OK(stateMachine()->dequePopFront("my-deque", item));
+  ASSERT_EQ(item, "5");
+
+  ASSERT_OK(stateMachine()->dequePopFront("my-deque", item));
+  ASSERT_EQ(item, "6");
+
+  ASSERT_OK(stateMachine()->dequePopFront("my-deque", item));
+  ASSERT_EQ(item, "7");
+
+  ASSERT_NOTFOUND(stateMachine()->dequePopFront("my-deque", item));
+}
+
 TEST_F(State_Machine, DequeOperations2) {
   std::vector<std::string> vec = {"item1", "item2", "item3", "item4"};
   int64_t length;