Create multiple Rails ActiveRecord records in one call/query

Question

In one of my Rails apps' AR classes, I ended up with an array of many newly initialised ActiveRecord objects.

I want to be able to save them to the DB in an efficient way, ideally, in one method call. At the moment, i have them wrapped inside a transaction.

Something like:

Object.transaction do
  @objects.map(&:save)
end

is there a more efficient solution to create/update an array of records?

Answer 1

You do right with wrapping everything into a transaction, becuase then the database flushes and updates indices only once.

You cannot insert many objects in a single SQL statement in standard SQL. MySQL can do that, but this is non-default. I doubt there is a huge performance advantage to this.

If this code is really time critical, you could run it asynchronously (by either moving it into a background thread - note there are issues with ActiveRecord and multithreading - or let it be executed by a worker. Or you could generate the SQL by hand - AR is not extremely efficient in doing so. However, I would go that way only if this is extremely critical, and would consider it a hack then.

Answer 2

I suggest using the activerecord-import gem until the mainline activerecord has support for bulk inserts.

It's fairly simple to use, for instance bulk inserting a bunch of "Rating" records:

# Example database record/model
class Rating < ActiveRecord::Base

end

ratings = []

# Create some fake data here..
100.times do |i|
    ratings << Rating.new({ stars: (rand * 5).to_i }) # random star rating
end

# Bulk import ratings (single query)
Rating.import(ratings)