Import CSV data faster in rails - ruby-on-rails

Question

I am building an import module to import a large set of orders from a csv file. I have a model called Order where the data needs to be stored.
A simplified version of the Order model is below
sku
quantity
value
customer_email
order_date
status
When importing the data two things have to happen
Any dates or currencies need to be cleaned up i.e. dates are represented as strings in the csv, this needs to be converted into a Rails Date object and currencies need to converted to a decimal by removing any commas or dollar signs
If a row already exists it has to be updated, the uniqueness is checked based on two columns.
Currently I use a simple csv import code
CSV.foreach("orders.csv") do |row|
order = Order.first_or_initialize(sku: row[0], customer_email: row[3])
order.quantity = row[1]
order.value= parse_currency(row[2])
order.order_date = parse_date(row[4])
order.status = row[5]
order.save!
end
Where parse_currency and parse_date are two functions used to extract the values from strings. In the case of the date it is just a wrapper for Date.strptime.
I can add a check to see if the record already exists and do nothing in case it already exists and that should save a little time. But I am looking for something that is significantly faster. Currently importing around 100k rows takes around 30 mins with an empty database. It will get slower as the data size increases.
So I am basically looking for a faster way to import the data.
Any help would be appreciated.
Edit
After some more testing based on the comments here I have an observation and a question. I am not sure if they should go here or if I need to open a new thread for the questions. So please let me know if I have to move this to a separate question.
I ran a test using Postgres copy to import the data from the file and it took less than a minute. I just imported the data into a new table without any validations. So the import can be much faster.
The Rails overhead seems to be coming from 2 places
The multiple database calls that are happening i.e. the first_or_initialize for each row. This ends up becoming multiple SQL calls because it has to first find the record and then update it and then save it.
Bandwidth. Each time the SQL server is called the data flows back and forth which adds up to a lot of time
Now for my question. How do I move the update/create logic to the database i.e. If an order already exists based on the sku and customer_email it needs to update the record else a new record needs to be created. Currently with rails I am using the first_or_initialize method to get the record in case it exists and update it, else I am creating a new one and saving it. How do I do that in SQL.
I could run a raw SQL query using ActiveRecord connection execute but I do not think that would be a very elegant way of doing it. Is there a better way of doing that?

Answer 1

Since ruby 1.9 fastcsv is now part of ruby core. You don't need to use a special gem. Simply use CSV.
With 100k records ruby takes 0.018 secs / record. In my opinion most of your time will be used within Order.first_or_initialize. This part of your code takes an extra roundtrip to your database. Initialization of an ActiveRecord takes it time too. But to realy be sure I would suggest that you benchmark your code.
Benchmark.bm do |x|
x.report("CSV evel") { CSV.foreach("orders.csv") {} }
x.report("Init: ") { 1.upto(100_000) {Order.first_or_initialize(sku: rand(...), customer_email: rand(...))} } # use rand query to prevent query caching
x.report('parse_currency') { 1.upto(100_000) { parse_currency(...} }
x.report('parse_date') { 1.upto(100_000) { parse_date(...} }
end
You should also watch memory consumption during your import. Maybe the garbage collection does not run often enough or objects are not cleaned up.
To gain speed you can follow Matt Brictson hint and bypass ActiveRecord.
You can try the gem activerecord-import or you can start to go parallel, for instance multiprocessing with fork or multithreading with Thread.new.