New Features

• Sequel now supports :lateral_subquery as a strategy when eager loading, eager graphing, and filtering by limited associations. For eager graphing and filtering, this strategy is likely to be the fastest strategy. Example with eager_graph:

  Artist.eager_graph_with_options(:first_10_albums,
    limit_strategy: :lateral_subquery).all
  # SELECT artists.id, artists.name,
  #        first_10_albums.id AS first_10_albums_id,
  #        first_10_albums.name AS first_10_albums_name,
  #        first_10_albums.artist_id,
  #        first_10_albums.release_date
  # FROM artists
  # LEFT OUTER JOIN LATERAL (
  #   SELECT *
  #   FROM albums
  #   WHERE (first_10_albums.artist_id = artists.id)
  #   ORDER BY release_date
  #   LIMIT 10
  # ) AS first_10_albums ON true
  # ORDER BY first_10_albums.release_date
  

  This is supported on all association types supporting limited associations:

  • one_to_many/one_to_one

  • many_to_many/one_through_one

  • many_through_many/one_through_many (many_through_many plugin)

  This requires native support for LATERAL subqueries, so it works on PostgreSQL, DB2, and HSQLDB. It does not work on MSSQL or SQLAnywhere, even with the LATERAL emulation offered by the mssql_emulate_lateral_with_apply extension.

  This is not currently used as the default eager_graph and filter by associations limit strategy on databases that support it. That change will likely be made in a future Sequel release.