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1秒で分かる joins, includes, preload, eager_load

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メソッド テーブル結合 クエリ 条件絞り込み Association キャッシュ 使い所
joins INNER JOIN 1 条件絞り込み
left_join LEFT OUTER JOIN 1 条件絞り込み
eager_load LEFT OUTER JOIN 1 Assiociation先をRubyで読む
preload なし 1以上 複数Assiciationを先読みしておく場合。複雑なJOINでslow queryになるような場合
includes 場合による 1以上 場合による eager_loadかpreloadを使い分けてる


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