Eager Loading

Eager loading allows you to efficiently load graphs of related objects in a single Verse query. It is useful when you know that you will need access to the related objects as part of a single operation, such as rendering a view. Eager loading can be used to avoid the N+1 query problem.

Eager loading in Verse is specified using the with query operator. The with operator takes an expression that specifies the related navigations to load. E.g.

let eager = db.from.artists.limit(1).with(a => a.albums);

for await (const artist of eager) {
  console.log(artist);
}

In this example, the albums navigation property will be eagerly loaded with the artist. It outputs:

{
  artistId: 1,
  name: 'AC/DC',
  albums: [
    {
      albumId: 1,
      title: 'For Those About To Rock We Salute You',
      artistId: 1
    },
    { albumId: 4, title: 'Let There Be Rock', artistId: 1 }
  ]
}

Multiple navigations can be specified as part of a single with operation. E.g. load an artist with their albums and tracks:

const artistAlbumsTracks = await db.from.artists
  .limit(1)
  .with(ar => ar.albums.with(al => al.tracks))
  .toArray();

Or, load a track with its album and artist:

const trackAlbumArtist = await db.from.tracks
  .limit(1)
  .with(t => t.album.artist)
  .toArray();

note

Verse uses a single query to load the related objects. This strategy is known as Left Join Fetching.