121 lines
3.6 KiB
Ruby
121 lines
3.6 KiB
Ruby
# frozen_string_literal: true
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class DeduplicateEpicIids < ActiveRecord::Migration[6.0]
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include Gitlab::Database::MigrationHelpers
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DOWNTIME = false
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INDEX_NAME = 'index_epics_on_group_id_and_iid'
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disable_ddl_transaction!
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class Epic < ActiveRecord::Base
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end
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class InternalId < ActiveRecord::Base
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class << self
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def generate_next(subject, scope, usage, init)
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InternalIdGenerator.new(subject, scope, usage, init).generate
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end
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end
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# Increments #last_value and saves the record
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#
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# The operation locks the record and gathers a `ROW SHARE` lock (in PostgreSQL).
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# As such, the increment is atomic and safe to be called concurrently.
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def increment_and_save!
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update_and_save { self.last_value = (last_value || 0) + 1 }
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end
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private
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def update_and_save(&block)
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lock!
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yield
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save!
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last_value
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end
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end
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# See app/models/internal_id
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class InternalIdGenerator
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attr_reader :subject, :scope, :scope_attrs, :usage, :init
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def initialize(subject, scope, usage, init = nil)
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@subject = subject
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@scope = scope
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@usage = usage
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@init = init
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raise ArgumentError, 'Scope is not well-defined, need at least one column for scope (given: 0)' if scope.empty? || usage.to_s != 'epics'
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end
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# Generates next internal id and returns it
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# init: Block that gets called to initialize InternalId record if not present
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# Make sure to not throw exceptions in the absence of records (if this is expected).
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def generate
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subject.transaction do
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# Create a record in internal_ids if one does not yet exist
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# and increment its last value
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#
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# Note this will acquire a ROW SHARE lock on the InternalId record
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record.increment_and_save!
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end
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end
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def record
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@record ||= (lookup || create_record)
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end
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def lookup
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InternalId.find_by(**scope, usage: usage_value)
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end
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def usage_value
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4 # see Enums::InternalId - this is the value for epics
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end
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# Create InternalId record for (scope, usage) combination, if it doesn't exist
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#
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# We blindly insert without synchronization. If another process
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# was faster in doing this, we'll realize once we hit the unique key constraint
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# violation. We can safely roll-back the nested transaction and perform
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# a lookup instead to retrieve the record.
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def create_record
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raise ArgumentError, 'Cannot initialize without init!' unless init
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instance = subject.is_a?(::Class) ? nil : subject
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subject.transaction(requires_new: true) do
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InternalId.create!(
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**scope,
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usage: usage_value,
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last_value: init.call(instance, scope) || 0
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)
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end
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rescue ActiveRecord::RecordNotUnique
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lookup
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end
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end
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def up
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duplicate_epic_ids = ApplicationRecord.connection.execute('SELECT iid, group_id, COUNT(*) FROM epics GROUP BY iid, group_id HAVING COUNT(*) > 1;')
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duplicate_epic_ids.each do |dup|
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Epic.where(iid: dup['iid'], group_id: dup['group_id']).last(dup['count'] - 1).each do |epic|
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new_iid = InternalId.generate_next(epic,
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{ namespace_id: epic.group_id },
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:epics, ->(instance, _) { instance.class.where(group_id: epic.group_id).maximum(:iid) }
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)
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epic.update!(iid: new_iid)
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end
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end
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add_concurrent_index :epics, [:group_id, :iid], unique: true, name: INDEX_NAME
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end
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def down
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# only remove the index, as we do not want to create the duplicates back
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remove_concurrent_index :epics, [:group_id, :iid], name: INDEX_NAME
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end
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end
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