2020-02-17 18:09:00 +00:00
|
|
|
# frozen_string_literal: true
|
|
|
|
|
|
|
|
# For large tables, PostgreSQL can take a long time to count rows due to MVCC.
|
|
|
|
# Implements a distinct and ordinary batch counter
|
|
|
|
# Needs indexes on the column below to calculate max, min and range queries
|
|
|
|
# For larger tables just set use higher batch_size with index optimization
|
|
|
|
# See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/22705
|
|
|
|
# Examples:
|
|
|
|
# extend ::Gitlab::Database::BatchCount
|
|
|
|
# batch_count(User.active)
|
|
|
|
# batch_count(::Clusters::Cluster.aws_installed.enabled, :cluster_id)
|
|
|
|
# batch_distinct_count(::Project, :creator_id)
|
|
|
|
module Gitlab
|
|
|
|
module Database
|
|
|
|
module BatchCount
|
|
|
|
def batch_count(relation, column = nil, batch_size: nil)
|
|
|
|
BatchCounter.new(relation, column: column).count(batch_size: batch_size)
|
|
|
|
end
|
|
|
|
|
|
|
|
def batch_distinct_count(relation, column = nil, batch_size: nil)
|
|
|
|
BatchCounter.new(relation, column: column).count(mode: :distinct, batch_size: batch_size)
|
|
|
|
end
|
|
|
|
|
|
|
|
class << self
|
|
|
|
include BatchCount
|
|
|
|
end
|
|
|
|
end
|
|
|
|
|
|
|
|
class BatchCounter
|
|
|
|
FALLBACK = -1
|
2020-03-10 09:08:10 +00:00
|
|
|
MIN_REQUIRED_BATCH_SIZE = 1_250
|
2020-02-17 18:09:00 +00:00
|
|
|
MAX_ALLOWED_LOOPS = 10_000
|
|
|
|
SLEEP_TIME_IN_SECONDS = 0.01 # 10 msec sleep
|
|
|
|
# Each query should take <<500ms https://gitlab.com/gitlab-org/gitlab/-/merge_requests/22705
|
2020-03-25 00:08:11 +00:00
|
|
|
DEFAULT_DISTINCT_BATCH_SIZE = 10_000
|
|
|
|
DEFAULT_BATCH_SIZE = 100_000
|
2020-02-17 18:09:00 +00:00
|
|
|
|
|
|
|
def initialize(relation, column: nil)
|
|
|
|
@relation = relation
|
|
|
|
@column = column || relation.primary_key
|
|
|
|
end
|
|
|
|
|
|
|
|
def unwanted_configuration?(finish, batch_size, start)
|
|
|
|
batch_size <= MIN_REQUIRED_BATCH_SIZE ||
|
|
|
|
(finish - start) / batch_size >= MAX_ALLOWED_LOOPS ||
|
|
|
|
start > finish
|
|
|
|
end
|
|
|
|
|
|
|
|
def count(batch_size: nil, mode: :itself)
|
|
|
|
raise 'BatchCount can not be run inside a transaction' if ActiveRecord::Base.connection.transaction_open?
|
|
|
|
raise "The mode #{mode.inspect} is not supported" unless [:itself, :distinct].include?(mode)
|
|
|
|
|
|
|
|
# non-distinct have better performance
|
2020-03-25 00:08:11 +00:00
|
|
|
batch_size ||= mode == :distinct ? DEFAULT_DISTINCT_BATCH_SIZE : DEFAULT_BATCH_SIZE
|
2020-02-17 18:09:00 +00:00
|
|
|
|
|
|
|
start = @relation.minimum(@column) || 0
|
|
|
|
finish = @relation.maximum(@column) || 0
|
|
|
|
|
|
|
|
raise "Batch counting expects positive values only for #{@column}" if start < 0 || finish < 0
|
|
|
|
return FALLBACK if unwanted_configuration?(finish, batch_size, start)
|
|
|
|
|
|
|
|
counter = 0
|
|
|
|
batch_start = start
|
|
|
|
|
|
|
|
while batch_start <= finish
|
|
|
|
begin
|
|
|
|
counter += batch_fetch(batch_start, batch_start + batch_size, mode)
|
|
|
|
batch_start += batch_size
|
|
|
|
rescue ActiveRecord::QueryCanceled
|
|
|
|
# retry with a safe batch size & warmer cache
|
|
|
|
if batch_size >= 2 * MIN_REQUIRED_BATCH_SIZE
|
|
|
|
batch_size /= 2
|
|
|
|
else
|
|
|
|
return FALLBACK
|
|
|
|
end
|
|
|
|
end
|
|
|
|
sleep(SLEEP_TIME_IN_SECONDS)
|
|
|
|
end
|
|
|
|
|
|
|
|
counter
|
|
|
|
end
|
|
|
|
|
|
|
|
def batch_fetch(start, finish, mode)
|
|
|
|
# rubocop:disable GitlabSecurity/PublicSend
|
|
|
|
@relation.select(@column).public_send(mode).where(@column => start..(finish - 1)).count
|
|
|
|
end
|
|
|
|
end
|
|
|
|
end
|
|
|
|
end
|