How Can I Optimize Rails Performance by Executing Raw SQL Queries?

Execute Raw SQL Queries in Rails

To improve the performance of a Rails application, you can consider utilizing raw SQL queries, especially on Heroku where requests are prone to timeout errors. Let's explore how to convert a specific code snippet to raw SQL:

@payments = PaymentDetail.joins(:project).order('payment_details.created_at desc')
@payment_errors = PaymentError.joins(:project).order('payment_errors.created_at desc')

@all_payments = (@payments + @payment_errors)

This code combines two associations, @payments and @payment_errors, into @all_payments. To execute this query as raw SQL, you can use the following steps:

sql = "SELECT * FROM payment_details
        JOIN projects ON payment_details.project_id = projects.id
        ORDER BY payment_details.created_at DESC
        UNION
        SELECT * FROM payment_errors
        JOIN projects ON payment_errors.project_id = projects.id
        ORDER BY payment_errors.created_at DESC;"

records_array = ActiveRecord::Base.connection.execute(sql)

The resulting records_array will contain an array of records obtained from your SQL query, allowing you to iterate through them as needed. This approach is faster than the original Ruby code as it bypasses Rails' ORM layer, directly accessing the database.

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