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# frozen_string_literal: true
module Gitlab
module Database
module Partitioning
class MonthlyStrategy
attr_reader :model, :partitioning_key
# We create this many partitions in the future
HEADROOM = 6.months
delegate :table_name, to: :model
def initialize(model, partitioning_key)
@model = model
@partitioning_key = partitioning_key
end
def current_partitions
result = connection.select_all(<<~SQL)
select
pg_class.relname,
parent_class.relname as base_table,
pg_get_expr(pg_class.relpartbound, inhrelid) as condition
from pg_class
inner join pg_inherits i on pg_class.oid = inhrelid
inner join pg_class parent_class on parent_class.oid = inhparent
inner join pg_namespace ON pg_namespace.oid = pg_class.relnamespace
where pg_namespace.nspname = #{connection.quote(Gitlab::Database::DYNAMIC_PARTITIONS_SCHEMA)}
and parent_class.relname = #{connection.quote(table_name)}
and pg_class.relispartition
order by pg_class.relname
SQL
result.map do |record|
TimePartition.from_sql(table_name, record['relname'], record['condition'])
end
end
# Check the currently existing partitions and determine which ones are missing
def missing_partitions
desired_partitions - current_partitions
end
private
def desired_partitions
[].tap do |parts|
min_date, max_date = relevant_range
parts << partition_for(upper_bound: min_date)
while min_date < max_date
next_date = min_date.next_month
parts << partition_for(lower_bound: min_date, upper_bound: next_date)
min_date = next_date
end
end
end
# This determines the relevant time range for which we expect to have data
# (and therefore need to create partitions for).
#
# Note: We typically expect the first partition to be half-unbounded, i.e.
# to start from MINVALUE to a specific date `x`. The range returned
# does not include the range of the first, half-unbounded partition.
def relevant_range
if first_partition = current_partitions.min
# Case 1: First partition starts with MINVALUE, i.e. from is nil -> start with first real partition
# Case 2: Rather unexpectedly, first partition does not start with MINVALUE, i.e. from is not nil
# In this case, use first partition beginning as a start
min_date = first_partition.from || first_partition.to
end
# In case we don't have a partition yet
min_date ||= Date.today
min_date = min_date.beginning_of_month
max_date = Date.today.end_of_month + HEADROOM
[min_date, max_date]
end
def partition_for(lower_bound: nil, upper_bound:)
TimePartition.new(table_name, lower_bound, upper_bound)
end
def connection
ActiveRecord::Base.connection
end
end
end
end
end
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