Cached a Pokémon's latest revision

This removes the need to use a GROUP or DISTINCT in eager-loading Pokémon on the front page. It duplicates data, but provisions are in place to keep the cache up-to-date. When a Pokémon record is updated, it is required that its cache points to the current revision. When a revision is created, it updates the Pokémon's cache to point to it, because a new revision will always be the most recent one, and it is impossible to reorder revisions.

This does not affect the number of queries used on the front page (see #1).

refs #4

1 files changed, 19 insertions, 0 deletions

@@ -0,0 +1,19 @@
+class CacheCurrentPokemonRevision < ActiveRecord::Migration[5.1]
+  def up
+    change_table :pokeviewer_pokemon do |t|
+      t.references :current, null: true
+    end
+
+    add_foreign_key :pokeviewer_pokemon, :pokeviewer_revisions,
+      column: :current_id
+
+    Pokeviewer::Pokemon.all.each do |p|
+      p.current_id = p.revisions.last.id
+      p.save!
+    end
+  end
+
+  def down
+    remove_column :pokeviewer_pokemon, :current_id
+  end
+end