Any change to describe a default source for a property that sets a new value on an update?

[shackra]

not sure how to ask this since I'm not a specialist on database things.

I have the following:

module default {
     abstract type DatedType {
          required property created_at -> datetime {
               default := std::datetime_current();
               readonly := true;
          };
          required property updated_at -> datetime {
               default := std::datetime_current();
          };
          property deleted_at -> datetime;
     }

     type User extending DatedType {
          required property username -> str {
               constraint exclusive;
          };
     }

     type Name extending DatedType {
          required property lang -> str;
          required property value -> str;

          constraint exclusive on ( (.lang, .value) );
     }
}

as you can see, I defined a type with fields that represent when the thing was created, when it was updated and when it was (soft) deleted. Setting a default upon creation is kind of easy since we have default in there. If we had something like default on update := std::datetime_current(); I could probably define updated_at as readonly := true as I did with created_at and let edgedb update that property for me when I'm updating some record.

Is this currently possible in some other way other than manually setting the new value on updates?

[elprans]

Currently, there isn't a schema-level way of implementing updated_at like you've described, so you'll need to keep including updated_at := std::datetime_current() in your UPDATE statements.

We are working on a general query rewrite system (see roadmap), which would allow arbitrary injection of operations into queries based on a condition (or unconditionally). Here's how (tentatively) your schema would look:

module default {
     abstract type DatedType {
          required property updated_at -> datetime;
          property deleted_at -> datetime;

          rule bump_updated_at on update {
              update DatedType set { updated_at := datetime_current() }
          }
     }
}

Or, in a more general audit log-style system:

module default {
     abstract type DatedType {
          required property updated_at -> datetime;
          property deleted_at -> datetime;

          rule audit on update {
              insert AuditLog { text := "updated " ++ DatedType.__type__.name ++ " on " ++ datetime_current() }
          }
     }
}

We expect this (or some part of it) to land in 2.0.

[ifiokjr]

Thanks for the answer. Is this still on the roadmap?

[elprans]

Yes, though not for 2.0.

[nrathaus]

Was this addressed? we are at version 4.0? or are you referring to something else when you mention 2.0

[raddevon]

Mutation rewrites were implemented in 3.0.

[nrathaus]

Thank you for the update, it wasn't clear from the issue above that it was - maybe it is a good idea to mark it at the title as [solved]?