Verwendung von HasCustomFields in einem Plugin

Entwickler
1

I have a model in a plugin. The model is Pfaffmananger::Server, the table is pfaffmanager_servers. For Reasons, I want to have custom fields for this model (I expect there to be ways that I want to extend the server data that are likely to be used only for a few instances and I don’t want a zillion mostly-unused fields in the model).

Here’s the migration that creates the table:

class CreatePfaffmanagerServerCustomField < ActiveRecord::Migration[6.0]
  def change
    create_table :pfaffmanager_server_custom_fields do |t|
      t.integer :server_id, null: false
      t.string :name, limit: 256, null: false
      t.text :value
      t.timestamps null: false
    end
    add_index :pfaffmanager_server_custom_fields, [:server_id, :name]
  end
end

If I use pfaffmanager_server_id instead of server_id the migration fails because it can’t find server_id, but when I use pfaffmanager_server_id for the field name, when I go to save a server after I create a custom field, I get:

  Pfaffmanager::ServerCustomField Load (0.4ms)  SELECT "pfaffmanager_server_custom_fields".* FROM "pfaffmanager_server_custom_fields" WHERE "pfaffmanager_server_custom_fields"."server_id" = 1
   (0.2ms)  ROLLBACK
PG::UndefinedColumn: ERROR:  column "pfaffmanager_server_id" of relation "pfaffmanager_server_custom_fields" does not exist
LINE 1: INSERT INTO pfaffmanager_server_custom_fields (pfaffmanager_...

So if the migration has field pfaffmanager_server_id the migration fails, and if the field name is server_id the save fails.

I’m looking at save_custom_fields in concers/has_custom_fields.rb, but can’t quite figure out if there’s some way to override that.

Is there something that I can do besides refactor the whole thing to use server rather than pfaffmanager_server?

2

Did you also update the add_index call to point to pfaffmanager_server_id?

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3

Thanks so much, David!

Yes. That could be my problem. I guess that’s the error message I should have included. And I can make the migration work with either field (though with pfaffmanager_server_id as the field name, the index name becomes > 63 characters, so I have to use a different name for the index.

Let me try again.

server_id as the field name

class CreatePfaffmanagerServerCustomField < ActiveRecord::Migration[6.0]
  def change
    create_table :pfaffmanager_server_custom_fields do |t|
      t.integer :server_id, null: false
      t.string :name, limit: 256, null: false
      t.text :value
      t.timestamps null: false
    end
    add_index :pfaffmanager_server_custom_fields, [:server_id, :name]
  end
end

Fails on save with:

 Pfaffmanager::ServerCustomField Load (3.8ms)  SELECT "pfaffmanager_server_custom_fields".* FROM "pfaffmanager_server_custom_fields" WHERE "pfaffmanager_server_custom_fields"."server_id" = 1
   (1.4ms)  ROLLBACK
PG::UndefinedColumn: ERROR:  column "pfaffmanager_server_id" of relation "pfaffmanager_server_custom_fields" does not exist
LINE 1: INSERT INTO pfaffmanager_server_custom_fields (pfaffmanager_...
                                                       ^

So it’s looking for pfaffmanager_server_id. Now, let’s use pfaffmanager_server_id.

pfaffmanager_server_id as field name

Here’s the migration:

class CreatePfaffmanagerServerCustomField < ActiveRecord::Migration[6.0]
  def change
    create_table :pfaffmanager_server_custom_fields do |t|
      t.integer :pfaffmanager_server_id, null: false
      t.string :name, limit: 256, null: false
      t.text :value
      t.timestamps null: false
    end
    add_index :pfaffmanager_server_custom_fields,
      [:pfaffmanager_server_id, :name],
      name: 'index_pfaffmanager_server_custom_fields_on_server_id_and_name'

  end
end

Here’s what happens when I try s.custom_fields (the above was able to return nil for this but didn’t fail until I tried to save a custom field). I register_custom_field_type here):

 pry(main)> s.custom_fields
   (1.1ms)  SELECT "pfaffmanager_server_custom_fields"."name", "pfaffmanager_server_custom_fields"."value" FROM "pfaffmanager_server_custom_fields" WHERE "pfaffmanager_server_custom_fields"."server_id" = 1 ORDER BY id asc
ActiveRecord::StatementInvalid: PG::UndefinedColumn: ERROR:  column pfaffmanager_server_custom_fields.server_id does not exist
LINE 1: ...e" FROM "pfaffmanager_server_custom_fields" WHERE "pfaffmana...
                                                             ^

from /home/pfaffman/.rbenv/versions/2.7.1/lib/ruby/gems/2.7.0/gems/rack-mini-profiler-2.3.0/lib/patches/db/pg.rb:69:in `exec_params'
Caused by PG::UndefinedColumn: ERROR:  column pfaffmanager_server_custom_fields.server_id does not exist
LINE 1: ...e" FROM "pfaffmanager_server_custom_fields" WHERE "pfaffmana...
                                                             ^

Now it’s looking for server_id.

So it seems like custom_fields wants it one way a save_custom_fields wants it the other.

It doesn’t care what the index name is, does it?

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4

I don’t think so, no

I think the second approach is probably the one to aim for (using pfaffman_server_id as the column name)

I wonder if overriding this method may help:

You can check the current value on the console like

Server.new.custom_fields_fk

If that’s server_id, then I suggest overriding that method in your Server model

class Server < ...
  def custom_fields_fk
    "pfaffman_server_id"
  end
end
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5

Or maybe it’s this bit :thinking:

https://github.com/discourse/discourse/blob/master/app/models/concerns/has_custom_fields.rb#L76-L77

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6

Thanks so much! So
Server.new.custom_fields_fk is pfaffmanager_server_id if I use pfaffmanager_serfver_id. So maybe I should use server_id and then override as you suggested above.

It looks like refresh_custom_fields_from_db is trying to use the wrong names. I don’t quite understand what _custom_fields.order... is doing.

https://github.com/discourse/discourse/blob/master/app/models/concerns/has_custom_fields.rb#L276-283

I’m going to see what happens if I use server_id and if I can then override custom_fields_fk

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7

Ha! You did it! Thanks so much. I switched it to server_id and then did this in my server.rb model:

    def custom_fields_fk
      @custom_fields_fk ||= "server_id"
    end

As long as that’s going to override that only for this model and not break user_custom_field and friends I think I should be ready to start beating myself over the head again on Best way to enforce permissions--controller or constraint?. And then I can add routes to do stuff like fill my new custom fields with . . . something.

I can’t thank you enough. You likely saved me a whole day. I owe you a :beer:!

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8

Great! :tada: If you can think of a way to make it more generic then that would certainly be PR-welcome.

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9

If something occurs to me I’ll let you know or submit a PR, but I have to think that a plugin that wants to use custom fields is pretty far out on the edge.

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10

OM_fk_G.

custom_fields_fk schien so dumm, dass ich annahm, es sei etwas, das ich löschen wollte und dem ich einen dummen Namen gegeben hatte, damit ich wüsste, dass es sicher zu löschen war. Es war später, also löschte ich es. Und dann schlugen meine Spezifikationen fehl.

Es gab sogar einen Kommentar mit einem Link zu diesem Thema im Code.

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