Need a help to update coherence cache values in c++

Question

Hi,
I need to update coherence cache value of a particular object.
Managed<ExposureHolderContract>::Handle contract =
cast<Managed<ExposureHolderContract>::Handle>(cache->get(vsName));
contract->setName("dsafd");
When i try to cast to a ManagedObject:: Handle it says
coherence::lang::ConstCastException: attempt to cast from a "const coherence::lang::Managed<ExposureHolderContract>" to a "coherence::lang::Managed<ExposureHolderContract>"
at void coherence::lang::coh_throw_const_cast(const std::type_info&, const std::type_info&)(ConstCastException.cpp:27)
at coherence::lang::coh_throw_const_cast(std::type_info const&, std::type_info const&)
<stack frame symbol unavailable>
<stack frame symbol unavailable>
<stack frame symbol unavailable>
<stack frame symbol unavailable>
<stack frame symbol unavailable>
at __libc_start_main
on thread "main"
In the documentation it says in order to call non static methods we need to retrieve the handle.
but when I try to cast to a handle it fails.
I'm inserting data to coherence cache by calling Managed::create method. Is this method making immutable object.
ExposureHolderContract tempEhc(contractId, name, date, age, weight);
Managed<ExposureHolderContract>::Handle ss = Managed<ExposureHolderContract>::create(tempEhc);
cache->put(String::create(contractId.c_str()), ss);
Please help me to update the recorde value.
regards,
sura

Answer 1

Hi Sura,
It is a matter of safety and correctness. The in-process caches return a locally held object, and thus if you made some change to it, that change would be visible within the in-process cache, while not visible to the remote cache. Thus future access to the in-process cache would see a value which does not actually exist in the remote cache. While it is true that if you modify it with the intent to immediately re-insert it this shrinks the window of incorrectness that window still exists, and of course the cache has no idea if you will ever reinsert the value. As for the effect on performance it should be insignificant if you actually do put it back in the cache as the cost of a cache update will easily be multiple orders of magnitude greater then the cost of the clone. Also remember there is no requirement to clone a value if you don't intend to mutate it, you can safely use it via the View. So the only time the performance cost of the clone could be considered significant is when you intend to mutate but not reinsert the data, but a clone is also necessary there as not cloning it would leave the in-process cache in an inconsistent state with respect to the remote cache.
Mark
Oracle Coherence