Update multiple rows with one query in rails

Question

The following Rails code results in 6 queries

people = { 1 => { "name" => "David" }, 2 => { "name" => "Jeremy" }, 3 => { "name" => "Tom" } }
Person.update(people.keys, people.values)

It will do TWO queries per updated row. One select and one update.

Is there a way to do the same task in Rails 4 with only one query (or only two queries)?

There are some information here on how to do it in MySQL, but not Rails: Multiple Updates in MySQL

Thanks.

short answer is no. because every transaction has to be atomic and isolated in a relational database. — Sam
– Sam, Commented Dec 10, 2013 at 23:58

Kaleidoscope · Accepted Answer · 2013-12-11 02:39:57Z

6

No, but not for the reason @Sam D gave.

It's because if you go through ActiveRecord, it's because you want to run validations, callbacks, etc. on the objects being updated. These validations and callbacks are not defined for a collection of objects.

You might say, "I don't care if they run." And that's fine. That's why rails gives you the ability to mass update through SQL directly.

answered Dec 11, 2013 at 2:39

Kaleidoscope

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2 Comments

user2725109 Over a year ago

Kaleidoscope, thank you for your explanation. As you mentioned, I don't care if validations and callbacks run. Do you have a link/reference for mass update through SQL in rails? Thanks.

Kaleidoscope Over a year ago

api.rubyonrails.org/classes/ActiveRecord/…

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