Missing operator< for HazelcastJsonValue

[RikeVoltz]

C++ compiler version: gcc 9.3
Hazelcast Cpp client version: 3.12
Hazelcast server version: 3.12
Number of the clients: 1
Cluster size, i.e. the number of Hazelcast cluster members: 3
OS version (Windows/Linux/OSX): Linux Ubuntu 20.04

Please attach relevant logs and files for client and server side.

Expected behaviour

.values(PagingPredicate(n)) method for IMap<std::string, HazelcastJsonValue> compiles successfully and produce correct output(first n values in the map)

Actual behaviour

/home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/impl/LazyEntryArrayImpl.h: In instantiation of ‘bool hazelcast::client::impl::LazyEntryArrayImpl<K, V>::Item::operator<(const hazelcast::client::impl::LazyEntryArrayImpl<K, V>::Item&) const [with K = std::__cxx11::basic_string<char>; V = hazelcast::client::HazelcastJsonValue]’:
/usr/include/c++/9/bits/predefined_ops.h:43:23:   required from ‘constexpr bool __gnu_cxx::__ops::_Iter_less_iter::operator()(_Iterator1, _Iterator2) const [with _Iterator1 = __gnu_cxx::__normal_iterator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item*, std::vector<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item, std::allocator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item> > >; _Iterator2 = __gnu_cxx::__normal_iterator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item*, std::vector<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item, std::allocator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item> > >]’
/usr/include/c++/9/bits/stl_algo.h:81:17:   required from ‘void std::__move_median_to_first(_Iterator, _Iterator, _Iterator, _Iterator, _Compare) [with _Iterator = __gnu_cxx::__normal_iterator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item*, std::vector<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item, std::allocator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item> > >; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’
/usr/include/c++/9/bits/stl_algo.h:1920:34:   required from ‘_RandomAccessIterator std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item*, std::vector<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item, std::allocator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item> > >; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’
/usr/include/c++/9/bits/stl_algo.h:1952:38:   required from ‘void std::__introsort_loop(_RandomAccessIterator, _RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item*, std::vector<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item, std::allocator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item> > >; _Size = long int; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’
/usr/include/c++/9/bits/stl_algo.h:1967:25:   required from ‘void std::__sort(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item*, std::vector<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item, std::allocator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item> > >; _Compare = __gnu_cxx::__ops::_Iter_less_iter]’
/usr/include/c++/9/bits/stl_algo.h:4867:18:   required from ‘void std::sort(_RAIter, _RAIter) [with _RAIter = __gnu_cxx::__normal_iterator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item*, std::vector<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item, std::allocator<hazelcast::client::impl::LazyEntryArrayImpl<std::__cxx11::basic_string<char>, hazelcast::client::HazelcastJsonValue>::Item> > >]’
/home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/impl/EntryArrayImpl.h:56:30:   required from ‘void hazelcast::client::impl::EntryArrayImpl<K, V>::sort(hazelcast::client::query::IterationType, const hazelcast::util::Comparator<std::pair<const K*, const V*> >*) [with K = std::__cxx11::basic_string<char>; V = hazelcast::client::HazelcastJsonValue]’
/home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/map/ClientMapProxy.h:809:21:   required from ‘std::vector<V> hazelcast::client::map::ClientMapProxy<K, V>::values(hazelcast::client::query::PagingPredicate<K, V>&) [with K = std::__cxx11::basic_string<char>; V = hazelcast::client::HazelcastJsonValue]’
/home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/IMap.h:642:49:   required from ‘std::vector<V> hazelcast::client::IMap<K, V>::values(hazelcast::client::query::PagingPredicate<K, V>&) [with K = std::__cxx11::basic_string<char>; V = hazelcast::client::HazelcastJsonValue]’
/home/rikevoltz/work/Projects/hazelcast_tests/main.cpp:25:43:   required from here
/home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/impl/LazyEntryArrayImpl.h:226:47: error: no match for ‘operator<’ (operand types are ‘hazelcast::client::HazelcastJsonValue’ and ‘hazelcast::client::HazelcastJsonValue’)
  226 |                                 return *value < *rhs.value;
      |                                        ~~~~~~~^~~~~~~~~~~~
In file included from /home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/config/NearCacheConfig.h:29,
                 from /home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/ClientConfig.h:33,
                 from /home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/map/impl/ClientMapProxyFactory.h:20,
                 from /home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/impl/HazelcastClientInstanceImpl.h:26,
                 from /home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/HazelcastClient.h:19,
                 from /home/rikevoltz/work/Projects/hazelcast_tests/main.cpp:1:
/home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/TypedData.h:83:28: note: candidate: ‘bool hazelcast::client::operator<(const hazelcast::client::TypedData&, const hazelcast::client::TypedData&)’
   83 |         bool HAZELCAST_API operator<(const TypedData &lhs, const TypedData &rhs);
      |                            ^~~~~~~~
/home/rikevoltz/.conan/data/hazelcast-cpp-client/3.12/_/_/package/49e7f59961e8ed9b7d1d33caa2e6d613b00b72a5/include/hazelcast/client/TypedData.h:83:55: note:   no known conversion for argument 1 from ‘hazelcast::client::HazelcastJsonValue’ to ‘const hazelcast::client::TypedData&’
   83 |         bool HAZELCAST_API operator<(const TypedData &lhs, const TypedData &rhs);
      |                                      ~~~~~~~~~~~~~~~~~^~~

The same situation with another type (string, int, etc.) compiles and works correctly. This is likely due to the missng operator< for HazelcastJsonValue.

Steps to reproduce the behaviour

auto client = hazelcast::client::HazelcastClient{config};
auto some_map = client.getMap<std::string, HazelcastJsonValue>("test_map");
some_map.put("some_key", HazelcastJsonValue("{\"id\":\"some_id\"}"));
some_map.put("some_other_key", HazelcastJsonValue("{\"id\":\"some_other_id\"}"));
some_map.put("another_key", HazelcastJsonValue("{\"id\":\"another_id\"}"));
auto predicate = PagingPredicate<std::string, HazelcastJsonValue>(2);
auto results = some_map.values(predicate);

[ihsandemir]

Hello @RikeVoltz Thanks for reporting this issue. It indeed is a problem. This is actually very much related to the solution of the other reported issue #589 . When we change the IMap::values as this, it compiles without a problem:

                std::vector<V> values() {
                    std::vector<serialization::pimpl::Data> dataResult = proxy::IMapImpl::valuesData();
                    size_t size = dataResult.size();
                    std::vector<V> values;
                    for (size_t i = 0; i < size; ++i) {
                        std::auto_ptr<V> value = toObject<V>(dataResult[i]);
                        values.push_back(*value);
                    }
                    return values;
                }

I will add related tests and issues into the 4.0 release for this issue as well.

Thanks again for reporting the problem.

[RikeVoltz]

Probably i missed something, but isn't this issue related to https://github.com/hazelcast/hazelcast-cpp-client/blob/v3.12/hazelcast/include/hazelcast/client/map/ClientMapProxy.h#L802 ?
Also I tried to fix as you propose in my fork (just to be confident), and this proposal fix just #589, but not #590, but I could have missed something or done something wrong, could you check it, please?

[ihsandemir]

Hello @RikeVoltz Yes, you are correct, I did not realize the PagingPredicate usage there, my bad. The PAgingPredicate uses a local sort operation at this line https://github.com/hazelcast/hazelcast-cpp-client/blob/v3.12/hazelcast/include/hazelcast/client/impl/LazyEntryArrayImpl.h#L226 which causes the problem. For this, we need a less operator.

By the way, at 4.0, we are changing PagingPredicate so that there is no sorting at the client side but it is performed at the server side, this is done for Java and i will be submitting this change PR in the following weeks for 4.0. When that is in place, it will also solve the problem, but until then, we need a less operator in place which is really trivial, if you are able to compile the project, I was able to compile your program with this fix in HazelcastJsonValue.cpp:

        bool HazelcastJsonValue::operator<(const HazelcastJsonValue &rhs) const {
            return jsonString < rhs.jsonString;
        }

HazelcastJsonValue.h:
class HAZELCAST_API HazelcastJsonValue {
public:
.....
bool operator<(const HazelcastJsonValue &rhs) const;

[burakcelebi]

Hi @RikeVoltz, super glad to hear that you are trying to fix it! Would you like to send a PR? We'd love to get a contribution from you. Please let us know :)

[RikeVoltz]

Hi @RikeVoltz, super glad to hear that you are trying to fix it! Would you like to send a PR? We'd love to get a contribution from you. Please let us know :)

Sure, thanks for the invitation, here you are :)

[burakcelebi]

Great, you are fast! :)