discourse/db/migrate/20190529002752_add_unique_constraint_to_shadow_accounts.rb
Sam Saffron 5c524ea8a4 FEATURE: introduce dedicated storage and DB constraints for anon users
Previously we used custom fields to denote a user was anonymous, this was
risky in that custom fields are prone to race conditions and are not
properly dedicated, missing constraints and so on.

The new table `anonymous_users` is properly protected. There is only one
possible shadow account per user, which is enforced using a constraint.

Every anonymous user will have a unique row in the new table.
2019-05-29 14:26:24 +10:00

60 lines
1.6 KiB
Ruby

# frozen_string_literal: true
class AddUniqueConstraintToShadowAccounts < ActiveRecord::Migration[5.2]
def up
create_table :anonymous_users do |t|
t.integer :user_id, null: false
t.integer :master_user_id, null: false
t.boolean :active, null: false
t.timestamps
t.index [:user_id], unique: true
t.index [:master_user_id], unique: true, where: 'active'
end
rows = DB.exec <<~SQL
DELETE FROM user_custom_fields
WHERE name = 'shadow_id' AND value in (
SELECT value
FROM user_custom_fields
WHERE name = 'shadow_id'
GROUP BY value
HAVING COUNT(*) > 1
)
SQL
if rows > 0
STDERR.puts "Removed #{rows} duplicate shadow users"
end
rows = DB.exec <<~SQL
INSERT INTO anonymous_users(user_id, master_user_id, created_at, updated_at, active)
SELECT value::int, user_id, created_at, updated_at, 't'
FROM user_custom_fields
WHERE name = 'shadow_id'
SQL
rows += DB.exec <<~SQL
INSERT INTO anonymous_users(user_id, master_user_id, created_at, updated_at, active)
SELECT f.user_id, value::int, f.created_at, f.updated_at, 'f'
FROM user_custom_fields f
LEFT JOIN anonymous_users a on a.user_id = f.user_id
WHERE name = 'master_id' AND a.user_id IS NULL
SQL
if rows > 0
STDERR.puts "Migrated #{rows} anon users to new structure"
end
DB.exec <<~SQL
DELETE FROM user_custom_fields
WHERE name in ('shadow_id', 'master_id')
SQL
end
def down
raise ActiveRecord::IrreversibleMigration
end
end