debian-mirror-gitlab/lib/gitlab/background_migration/backfill_design_internal_ids.rb

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2021-01-29 00:20:46 +05:30
# frozen_string_literal: true
module Gitlab
module BackgroundMigration
# Backfill design.iid for a range of projects
class BackfillDesignInternalIds
# See app/models/internal_id
# This is a direct copy of the application code with the following changes:
# - usage enum is hard-coded to the value for design_management_designs
# - init is not passed around, but ignored
class InternalId < ActiveRecord::Base
def self.track_greatest(subject, scope, new_value)
InternalIdGenerator.new(subject, scope).track_greatest(new_value)
end
# Increments #last_value with new_value if it is greater than the current,
# and saves the record
#
# The operation locks the record and gathers a `ROW SHARE` lock (in PostgreSQL).
# As such, the increment is atomic and safe to be called concurrently.
def track_greatest_and_save!(new_value)
update_and_save { self.last_value = [last_value || 0, new_value].max }
end
private
def update_and_save(&block)
lock!
yield
# update_and_save_counter.increment(usage: usage, changed: last_value_changed?)
save!
last_value
end
end
# See app/models/internal_id
class InternalIdGenerator
attr_reader :subject, :scope, :scope_attrs
def initialize(subject, scope)
@subject = subject
@scope = scope
raise ArgumentError, 'Scope is not well-defined, need at least one column for scope (given: 0)' if scope.empty?
end
# Create a record in internal_ids if one does not yet exist
# and set its new_value if it is higher than the current last_value
#
# Note this will acquire a ROW SHARE lock on the InternalId record
def track_greatest(new_value)
subject.transaction do
record.track_greatest_and_save!(new_value)
end
end
def record
@record ||= (lookup || create_record)
end
def lookup
InternalId.find_by(**scope, usage: usage_value)
end
def usage_value
10 # see Enums::InternalId - this is the value for design_management_designs
end
# Create InternalId record for (scope, usage) combination, if it doesn't exist
#
# We blindly insert without synchronization. If another process
# was faster in doing this, we'll realize once we hit the unique key constraint
# violation. We can safely roll-back the nested transaction and perform
# a lookup instead to retrieve the record.
def create_record
subject.transaction(requires_new: true) do
InternalId.create!(
**scope,
usage: usage_value,
last_value: 0
)
end
rescue ActiveRecord::RecordNotUnique
lookup
end
end
attr_reader :design_class
def initialize(design_class)
@design_class = design_class
end
def perform(relation)
start_id, end_id = relation.pluck("min(project_id), max(project_id)").flatten
table = 'design_management_designs'
ActiveRecord::Base.connection.execute <<~SQL
WITH
starting_iids(project_id, iid) as (
SELECT project_id, MAX(COALESCE(iid, 0))
FROM #{table}
WHERE project_id BETWEEN #{start_id} AND #{end_id}
GROUP BY project_id
),
with_calculated_iid(id, iid) as (
SELECT design.id,
init.iid + ROW_NUMBER() OVER (PARTITION BY design.project_id ORDER BY design.id ASC)
FROM #{table} as design, starting_iids as init
WHERE design.project_id BETWEEN #{start_id} AND #{end_id}
AND design.iid IS NULL
AND init.project_id = design.project_id
)
UPDATE #{table}
SET iid = with_calculated_iid.iid
FROM with_calculated_iid
WHERE #{table}.id = with_calculated_iid.id
SQL
# track the new greatest IID value
relation.each do |design|
current_max = design_class.where(project_id: design.project_id).maximum(:iid)
scope = { project_id: design.project_id }
InternalId.track_greatest(design, scope, current_max)
end
end
end
end
end