ruby 41 lines · 9 steps

Batch-processing dormant users in Rails

A service object that archives, purges, and exports large user sets without loading everything into memory.

Explained by highlit
Rails Intermediate batch-processing activerecord service-object memory-efficiency bulk-updates
1class InactiveAccountCleanup
2 BATCH_SIZE = 500
3 INACTIVITY_THRESHOLD = 18.months
4 
5 def call
6 cutoff = INACTIVITY_THRESHOLD.ago
7 dormant = User.where("last_active_at < ?", cutoff).where(archived_at: nil)
8 
9 dormant.find_each(batch_size: BATCH_SIZE) do |user|
10 user.update_columns(archived_at: Time.current)
11 AccountArchivedMailer.with(user: user).farewell_notice.deliver_later
12 end
13 end
14 
15 def purge_soft_deleted!
16 scope = User.where.not(deleted_at: nil).where("deleted_at < ?", 30.days.ago)
17 
18 scope.in_batches(of: BATCH_SIZE) do |relation|
19 ids = relation.pluck(:id)
20 
21 Comment.where(user_id: ids).delete_all
22 ApiToken.where(user_id: ids).delete_all
23 relation.delete_all
24 
25 Rails.logger.info("Purged #{ids.size} users, oldest id #{ids.min}")
26 end
27 end
28 
29 def export_report(io)
30 User.select(:id, :email, :last_active_at)
31 .order(:id)
32 .find_in_batches(batch_size: 1_000) do |group|
33 rows = group.map do |user|
34 [user.id, user.email, user.last_active_at&.iso8601]
35 end
36 
37 io.write(rows.map { |row| row.join(",") }.join("\n"))
38 io.write("\n")
39 end
40 end
41end
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Batched iteration keeps memory flat when acting on tables that don't fit comfortably in RAM.
  2. 2Choosing update_columns, delete_all, or a mailer per row is a deliberate trade of callbacks and speed.
  3. 3Deleting dependent rows by foreign key before the parent avoids orphaned records when callbacks are bypassed.

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