Dynamic select from jsonb

Hi,

I’m creating dynamic system and some values are stored in jsonb in Postgres. I would like to filter values from json by selecting like this:

select values->>name, values->>description from cms.contents c where c.type = 'product'

with linq query:

db.Contents.Select("name", "description") because input is List<string>

How can I do that in linq2db? I tried something like SqlKata but I don’t want change my ORM because of a few jsonb columns. 😦

Thanks! Pavel

[sdanyliv]

Yes, it is possible via dynamic expressions. Try to produce expression tree dynamically like this one:

Expression<Func<Context, SomeResult>> mapper = 
   c => new SomeResult
   { 
       Id = c.Id,
       Values = new Dictionary<string, string> { 
           {"name", c.Values.JsonProp("name")},
           {"description", c.Values.JsonProp("description")},
       }
   }

[sdanyliv]

Still cannot handle whole idea

[Sql.Expression("{0}->>{1}", ServerSideOnly = true)]
public static string JsonProp(this JObject obj, [SqlQueryDependent] string propName)
   => throw new NotImplementedException();

db.GetTable<Content>()
   .Where(c => c.Values.JsonProp("name") == someName)
   .Select(c => new { name.= c.Values.JsonProp("name"), description = c.Values.JsonProp("description")})

For making projection whole dynamic, I think yes you have to create class dynamically. I need to check one solution, maybe we can convert JObject to Dictionary in projection automatically