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includes_conditions

🔗 Eager Loading Conditions with includes and references​

To avoid the N+1 problem while filtering on associations, combine includes with references and where. references tells Rails to generate proper JOINs for the WHERE clause.

# Fetch posts that have comments by author with ID 42
posts = Post.includes(:comments)
            .references(:comments)
            .where(comments: { author_id: 42 })