JOIN (Q.on) query returns nothig.

[Lao-Ax]

I have 3 linked tables. One is omitted.
First table

export default class Tag extends Model {
	static table = 'tags';

	static associations = {
		docs: { type: 'has_many', foreignKey: 'tag_id' }
	};

	@field('name') name;
	@field('color') color;
	@children('docs') docs;
}

It has two records: [ ('t1', 'tag1', 'green'), ('id2', 'tag2', 'red') ]

Second table

export default class Doc extends Model {
	static table = 'docs';

	static associations = {
		tags: { type: 'belongs_to', key: 'tag_id' },
		authors: { type: 'belongs_to', key: 'author_id' }
	};

	@field('tag_id') tagId;
	@field('author_id') authorId;
	@field('done') done;
	@relation('tags', 'tag_id') tag;
	@relation('authors', 'author_id') author;
}

It has one record: [ ('d1', 't1', 'some_author_id', 'not done') ]

I try to get dos marked by tag1:

const collection = db.get('docs');
const records= await collection.query(Q.on('tags', 'name', 'tag1')).fetch();

and I have got [].

What I'm doing wrong?

[Lao-Ax]

I'm very frustrated. The code is fully OK. I've just deleted the app, inputed the data once again, run the query and everything is in place.
So, threat this like an example of quering :)