DB Migration chokes deployment

[icarito]

This migration appears stuck in production deployment process:

class AddFirstTagPoster < ActiveRecord::Migration[5.1]
  def find_and_update
    User.joins(:node).where('node.status = ?', 1).each do |user|
      if user.nodes.present?
        node = user.nodes.first
        node.add_tag('first-time-post', user)
      end
    end
  end

  def up
    find_and_update
  end
end

[icarito]

My impression is that joining Users and Node is heavy...

[jywarren]

ahhhhhhh i should've caught that. Sorry! Should we refactor that and try running again?

…

On Wed, Mar 6, 2019 at 1:57 AM Sebastian Silva ***@***.***> wrote: My impression is that joining Users and Node is heavy... — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#4924 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABfJ8I9CauUA61xzSjrg8oS3vNh1zpoks5vT2aygaJpZM4bgL4r> .

[namangupta01]

What exactly we want to do here?

[jywarren]

I think we need to add additional conditions to the User...() call so that we aren't trying to fetch all user records. But according to previous tests, this should only be calling 7k records, which isn't all that much:

> User.joins(:node).where('node.status = ?', 1).count
=> 7278
> User.joins(:comments).count
=> 15201

@icarito do you think even 7k records would be too many and could be causing this?

[jywarren]

Testing the above on live db console to benchmark...

[jywarren]

I wonder if it's just taking a really long time to go through and make all the tags, but that potentially it's not actually hanging but just taking a really long time to iterate through 7k records and do this for each one?

[jywarren]

OK, compare:

> User.joins(:node).where('node.status = ?', 1).count => 7278

User.joins(:node).where('node.status = ?', 1).distinct.count => 1407

User.includes(:node).where(node: { status: 1 }).count => 1407

Gah, ok well that helps a bit...

[jywarren]

https://guides.rubyonrails.org/active_record_querying.html#specifying-conditions-on-eager-loaded-associations

[jywarren]

Attempted fix here: 1737876

[jywarren]

Deploying this now... hoping!

[jywarren]

Done! It worked!