102 lines
3.6 KiB
Ruby
102 lines
3.6 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module Database
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module Count
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# This strategy counts based on PostgreSQL's statistics in pg_stat_user_tables.
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#
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# Specifically, it relies on the column reltuples in said table. An additional
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# check is performed to make sure statistics were updated within the last hour.
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#
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# Otherwise, this strategy skips tables with outdated statistics.
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#
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# There are no guarantees with respect to the accuracy of this strategy. Runtime
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# however is guaranteed to be "fast", because it only looks up statistics.
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class ReltuplesCountStrategy
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attr_reader :models
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def initialize(models)
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@models = models
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end
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# Returns a hash of the table names that have recently updated tuples.
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#
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# @returns [Hash] Table name to count mapping (e.g. { 'projects' => 5, 'users' => 100 })
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def count
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size_estimates
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rescue *CONNECTION_ERRORS
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{}
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end
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private
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# Models using single-type inheritance (STI) don't work with
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# reltuple count estimates. We just have to ignore them and
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# use another strategy to compute them.
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def non_sti_models(models)
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models.reject { |model| sti_model?(model) }
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end
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def non_sti_table_names(models)
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non_sti_models(models).map(&:table_name)
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end
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def sti_model?(model)
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model.column_names.include?(model.inheritance_column) &&
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model.base_class != model
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end
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def table_to_model_mapping
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@table_to_model_mapping ||= models.each_with_object({}) { |model, h| h[model.table_name] = model }
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end
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def table_to_model(table_name)
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table_to_model_mapping[table_name]
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end
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def size_estimates(check_statistics: true)
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results = {}
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models.group_by { |model| model.connection_db_config.name }.map do |db_name, models_for_db|
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base_model = Gitlab::Database.database_base_models[db_name]
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tables = non_sti_table_names(models_for_db)
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# Querying tuple stats only works on the primary. Due to load balancing, the
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# easiest way to do this is to start a transaction.
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base_model.transaction do
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Gitlab::Database::SharedModel.using_connection(base_model.connection) do
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get_statistics(tables, check_statistics: check_statistics).each do |row|
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model = table_to_model(row.table_name)
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results[model] = row.estimate
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end
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end
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end
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end
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results
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end
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# Generates the PostgreSQL query to return the tuples for tables
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# that have been vacuumed or analyzed in the last hour.
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#
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# @param [Array] table names
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# @returns [Hash] Table name to count mapping (e.g. { 'projects' => 5, 'users' => 100 })
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def get_statistics(table_names, check_statistics: true)
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time = 6.hours.ago
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query = ::Gitlab::Database::PgClass.joins("LEFT JOIN pg_stat_user_tables ON pg_stat_user_tables.relid = pg_class.oid")
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.where(relname: table_names)
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.where('schemaname = current_schema()')
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.select('pg_class.relname AS table_name, reltuples::bigint AS estimate')
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if check_statistics
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query = query.where('last_vacuum > ? OR last_autovacuum > ? OR last_analyze > ? OR last_autoanalyze > ?',
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time, time, time, time)
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end
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query
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end
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end
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end
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end
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end
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