Bulk Insert records into Active Record table

Question

I found that my Model.create! statements were taking a very long time to run when I added a large number of records at once. Looked at ActiveRecord-Import but it didn't work with an array of hashes (which is what I have and which I think is pretty common). How can I improve the performance?

Answer 1

Use the activerecord-import gem. Let us say you are reading a CSV file and generating a Product catalogue and you want to insert records in batches of 1000:

batch,batch_size = [], 1_000 
CSV.foreach("/data/new_products.csv", :headers => true) do |row|
  batch << Product.new(row)

  if batch.size >= batch_size
    Product.import batch
    batch = []
  end
end
Product.import batch

Answer 2

Thanks to Chris Heald @cheald for his 2009 article, with showed me that the best way to go was the multi-row insert command.

Added the following code to my initializers/active_record.rb file, changed my Model.create!(...) calls to Model.import!(...) and away it goes. A couple caveats:

1) It does not validate the data.
2) It uses the form of the SQL INSERT command that reads like ...

INSERT INTO <table> (field-1, field-2, ...) 
       VALUES (value-1-1, value-1-2, ...), (value-2-1, value-2-2, ...), ...`

... which may not be the correct syntax for all databases, but it works with Postgres. It would not be difficult to alter the code for the appropriate syntax for your SQL version.

In my particular case, inserting 19K+ records into a simple table on my development machine (MacBook Pro with 8GB RAM, 2.4GHz Intel Core i5 and and SSD) went from 223 seconds using 'model.create!' to 7.2 seconds using a 'model.import!'.

class ActiveRecord::Base

  def self.import!(record_list)
    raise ArgumentError "record_list not an Array of Hashes" unless record_list.is_a?(Array) && record_list.all? {|rec| rec.is_a? Hash }
    key_list, value_list = convert_record_list(record_list)        
    sql = "INSERT INTO #{self.table_name} (#{key_list.join(", ")}) VALUES #{value_list.map {|rec| "(#{rec.join(", ")})" }.join(" ,")}"
    self.connection.insert_sql(sql)
  end

  def self.convert_record_list(record_list)
    key_list = record_list.map(&:keys).flatten.uniq.sort

    value_list = record_list.map do |rec|
      list = []
      key_list.each {|key| list <<  ActiveRecord::Base.connection.quote(rec[key]) }
      list
    end

    return [key_list, value_list]
  end
end

Answer 3

I started running into problems with large numbers of records (> 10000), so I modified the code to work in groups of 1000 records at a time. Here is a link to the new code:

https://gist.github.com/jackrg/76ade1724bd816292e4e

Answer 4

You can also use the activerecord-insert_many gem. Just make an array of objects!

events = [{name: "Movie Night", time: "10:00"}, {name: "Tutoring", time: "7:00"}, ...]

Event.insert_many(events)

Answer 5

Using a transaction speeds up bulk inserts a lot!

Model.transaction do
    many.times{ Model.create! }
end

If multiple Models are involved, do a Model.transaction for each model, which is affected:

Model1.transaction do
    Model2.transaction do
        many.times do
            m1 = Model1.create!
            m1.add_model2
        end
    end
end