Add DuckDB tests

[Giorgi]

Test for #1952

The NuGet package includes native libraries too.

[mgravell]

This is probably fine - I will need to try it locally - will try to do tomorrow

[mgravell]

I'm happy to merge as-is, but FYI: this doesn't actually work for netfx - I see that there's a netstandard2.0 package in the nuget, but: it doesn't seem to work; it doesn't work in the tests here, and doesn't work in standalone packages either; example:

<Project Sdk="Microsoft.NET.Sdk">
    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net472</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <LangVersion>12</LangVersion>
    </PropertyGroup>
    <ItemGroup>
        <PackageReference Include="DuckDB.NET.Data.Full" Version="0.9.0.3"/>
    </ItemGroup>
</Project>

with:

using DuckDB.NET.Data;

using var conn = new DuckDBConnection("Data Source=:memory:");
conn.Open();

gives:

Unhandled Exception: System.DllNotFoundException: Unable to load DLL 'duckdb': The specified module could not be found. (Exception from HRESULT: 0x8007007E)
   at DuckDB.NET.NativeMethods.Startup.DuckDBOpen(String path, DuckDBDatabase& database, DuckDBConfig config, IntPtr& error)
   at DuckDB.NET.Data.Internal.ConnectionManager.GetConnectionReference(DuckDBConnectionString connectionString)
   at DuckDB.NET.Data.DuckDBConnection.Open()
   at Program.<Main>$(String[] args) in C:\Code\ConsoleApp7\ConsoleApp7\Program.cs:line 4

The packaging might not be right. I haven't looked to see what you're packaging and how - it doesn't look like there are native binaries in the nupkg itself, so I'm guessing that they are embedded resources in the dll? More of a topic for DuckDB, but you might prefer to embed them in the nupkg rather than the dll; I also haven't checked to see how the unmanaged dll works re cross-platform (normally I'd expect to see a bunch of platform-specific native dlls in the nupkg, for this purpose)

(let me know if you need any help with any of this)

[mgravell]

see also:

where the failure is:

DuckDB is unavailable: Unable to load DLL 'duckdb': The specified module could not be found. (Exception from HRESULT: 0x8007007E)

[Giorgi]

It doesn't work for netfx but works for net core. The native libraries are under runtime folder but netfx doesn't know how to load them: https://stackoverflow.com/questions/56154884/nuget-package-not-copying-native-dlls-on-build

[Giorgi]

The native libraries are in another package that the top level depends on DuckDB.NET.Bindings.Full

[mgravell]

logged here: Giorgi/DuckDB.NET#151 - I guess the key bit is "it didn't work"

[mgravell]

@Giorgi ah, it is 32-bit vs 64-bit; see 151

[mgravell]

(I still can't get the tests to run in netfx, but my standalone console works 🤷)

[mgravell]

It doesn't work for netfx but works for net core. The native libraries are under runtime folder but netfx doesn't know how to load them: https://stackoverflow.com/questions/56154884/nuget-package-not-copying-native-dlls-on-build

I'm using SDK-style project, so this should work; it now works for the standalone console, if I explicitly use x64 rather than the implicit anycpu which is picking up x86