No translation for dictionary indexer on jsonb columns

Consider the following entity:

public class User
{
      [Key]
      public Guid Id { get; set; }

      [Column(TypeName = "jsonb")]
      public Dictionary<string, object> Properties { get; set; }
}

And then querying:

context.User.Where(x => x.Properties["something"] == "something else").ToList();

Ends up not being able to translate.

Translating the method call of get_Item to something npgsql can understand has proven to be difficult. And one would assume translating it into the proper binding is not possible due to the dynamic nature. I would assume some internal work is needed to properly translate get_Item into sql directly instead.

I looked into perhaps doing a custom Visitor to handle this case but my Expression knowledge lacks in this case and it does not seem possible in the end anyways. Also to clarify, changing the dictionary to a JsonDocument type is not warranted in this case.

[roji]

Thanks for the added details. Yeah, mapping Dictionary<string, object> and translating the indexer seems like a very valid scenario to me - I’ve noted it for 6.0 (I’ll probably be doing work on this in EF itself). Jsonpath is definitely also on my list, tracked by https://github.com/npgsql/efcore.pg/issues/1045 for PG specifically - but again I’ll look into this from a cross-database perspective for 6.0.

Will keep this open for now to specifically track dictionary indexer for EFCore.PG.

[roji]

This is indeed unsupported at the moment. The mapping itself works since System.Text.Json can serialize/deserialize dictionary as JSON, but the query pipeline does not support the translating of the dictionary indexer, as you’ve noticed. There’s nothing impossible or special about it - just like we translate the various methods on JsonDocument, it’s possible to translate this.

We are planning a general JSON overhaul for EF Core 6.0 - not just for the PostgreSQL provider - so at this point I’m a bit reluctant to make this change. Is there any specific reason you don’t want to use JsonDocument, except for aesthetics?