Updating entity mapped to JSONB column does not update the database

[andrewslavin]

Steps to reproduce:

1. Create an EF Core project with SomeEntity entity as described on this page https://www.npgsql.org/efcore/mapping/json.html#poco-mapping in the POCO mapping section.
2. Add code that creates a new instance of SomeEntity and calls SaveChanges() to persist it to the database.
3. Add code that reads SomeEntity back (on a different instance of DbContext), updates it as follows someEntity.Customer.Age = <different_number_from_what_it_currently_is>, and calls SaveChanges().

The expected outcome is that customer age will be updated in the DB, but actually no change happens. Looking at the entities in the ChangeTracker, I can see that SomeEntity is being tracked as Unchanged. I guess this is understandable - for EF to pick up the change, one of the SomeEntity instance properties needs to change. E.g. this produces the desired result: someEntity.Customer = new Customer { Age = <new_value>, <set all other props to old values>}.

Is there a way to make EF behave as expected? If not, it would be good to talk about this behaviour on the page I linked above.

[roji]

Sorry for not answering here sooner.

Version 8.0 of the provider introduced support for the standard EF ToJson() support, which is generally better than Npgsql's traditional POCO mapping; as a result, the latter is now discouraged (see the 8.0 release notes, as well as the updated JSON docs).

Note that DOM mapping (via JsonDocument/JsonElement) may still make sense in some scenarios, and performing full change-tracking there is tracked by #3314.