Question

What is your roadmap for supporting other types? I'm particularly interested in json, jsonb and arrays (of floats).

Thanks -- Don

lganzzzo commented 3 years ago

Hello @dsmyth ,

Just updated the readme with the list of supported data-types. :)

What is your roadmap for supporting other types? I'm particularly interested in json, jsonb and arrays (of floats).

At the moment there is no roadmap for this. A better types-support will be developed dynamically based on community requests/PRs/and ease of implementation.

My estimations:

Arrays - easy - might be added pretty soon (others also asked for array support).
JSON - hard - investigation needed.
JSONB - hard - investigation needed.

Also, if you'd like to contribute - I'll provide the necessary assistance.

Best Regards, Leonid

dsmyth commented 3 years ago

I'm willing to try adding arrays -- my current need is a float4 array. If I catch it in the deserializer, I can see my data in memory: In pgsql:

twdb=# select boxbounds from captures where captureid=1;
        boxbounds        
-------------------------
 {0,1.1,2.2,3.3,4.4,5.5}

In gdb:

(gdb) x/68xb data.data
0x7f45c40f8740: 0x00    0x00    0x00    0x01    0x00    0x00    0x00    0x00
0x7f45c40f8748: 0x00    0x00    0x02    0xbc    0x00    0x00    0x00    0x06
0x7f45c40f8750: 0x00    0x00    0x00    0x01    0x00    0x00    0x00    0x04
0x7f45c40f8758: 0x00    0x00    0x00    0x00    0x00    0x00    0x00    0x04
0x7f45c40f8760: 0x3f    0x8c    0xcc    0xcd    0x00    0x00    0x00    0x04
0x7f45c40f8768: 0x40    0x0c    0xcc    0xcd    0x00    0x00    0x00    0x04
0x7f45c40f8770: 0x40    0x53    0x33    0x33    0x00    0x00    0x00    0x04
0x7f45c40f8778: 0x40    0x8c    0xcc    0xcd    0x00    0x00    0x00    0x04
0x7f45c40f8780: 0x40    0xb0    0x00    0x00

Offset 58, 68, 70, 78 and 80 are the IEEE754 representation of the 4 byte floating point numbers in the field. Can you point me to how to parse this data structure?

Here's my start at adding the deserializer method:

oatpp::Void Deserializer::deserializeArray(const Deserializer* _this, const InData& data, const Type* type) {

    (void) _this;
    (void) type;

    switch(data.oid) {
        case FLOAT4ARRAYOID: return oatpp::Vector<Float32>();
        case FLOAT8ARRAYOID: return oatpp::Vector<Float64>();
    }

    if(data.isNull) {
        return oatpp::postgresql::Uuid();
    }

    return postgresql::Uuid((p_char8)data.data);
}

lganzzzo commented 3 years ago

Hey @dsmyth ,

Please create a draft PR so that we can collaborate on this feature.

Can you point me to how to parse this data structure?

First, let's start by creating a template method for parsing arrays to oatpp::Vector, oatpp::List, oatpp::UnorderedSet. We ganna have a template method because functionality will be mostly the same:

Let's use JSON deserializer as a reference - See JSON array deserialization

template<class Collection> 
oatpp::Void Deserializer::deserializeArray(const Deserializer* _this, const InData& data, const Type* type) {

  auto polymorphicDispatcher = static_cast<const typename Collection::Class::PolymorphicDispatcher*>(type->polymorphicDispatcher);

  auto itemType = *type->params.begin(); // Get "wanted" type of the list item

  // TODO - check that wanted itemType is compatible with the data OID item type.

  if(data.isNull) {
    // return nullptr with the type. - after we've checked the type.
    return oatpp::Void(nullptr, type);
  }

  auto listWrapper = polymorphicDispatcher->createObject(); // Instantiate list of the "wanted" type
  const auto& list = listWrapper.template staticCast<Collection>();

  // TODO - read "InData data" and push items to list

  return list;

}

Then, reference this method by referencing it here - https://github.com/oatpp/oatpp-postgresql/blob/master/src/oatpp-postgresql/mapping/Deserializer.cpp#L72 - for Vector, List, and UnorderedSet

oatpp / oatpp-postgresql

API question: other types #3

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