Continuous Aggregates DSL

[jonatas]

It's related to #64.

Full example:

# lib/timescaledb/continuous_aggregates.rb
require 'bundler/inline'

gemfile do
  source 'https://rubygems.org'
  gem 'timescaledb', path: '.'
  gem 'pry'
end

class Download < ActiveRecord::Base
  extend Timescaledb::ActsAsHypertable
  include Timescaledb::ContinuousAggregatesHelper

  acts_as_hypertable time_column: 'ts'

  scope :total_downloads, -> { select("count(*) as total") }
  scope :downloads_by_gem, -> { select("gem_name, count(*) as total").group(:gem_name) }
  scope :downloads_by_version, -> { select("gem_name, gem_version, count(*) as total").group(:gem_name, :gem_version) }

  continuous_aggregates(
    timeframes: [:minute, :hour, :day, :month],
    scopes: [:total_downloads, :downloads_by_gem, :downloads_by_version],
    refresh_policy: {
      minute: { start_offset: "10 minutes", end_offset: "1 minute", schedule_interval: "1 minute" },
      hour:   { start_offset: "4 hour",     end_offset: "1 hour",   schedule_interval: "1 hour" },
      day:    { start_offset: "3 day",      end_offset: "1 day",    schedule_interval: "1 day" },
      month:  { start_offset: "3 month",    end_offset: "1 day",  schedule_interval: "1 say" }
  })
end

ActiveRecord::Base.establish_connection(ENV['DATABASE_URL'])
ActiveRecord::Base.connection.instance_exec do
  ActiveRecord::Base.logger = Logger.new(STDOUT)
  Download.drop_continuous_aggregates

  drop_table(:downloads, force: :cascade) if Download.table_exists?

  hypertable_options = {
    time_column: 'ts',
    chunk_time_interval: '1 day',
    compress_segmentby: 'gem_name, gem_version',
    compress_orderby: 'ts DESC',
    compression_interval: '7 days'
  }

  create_table(:downloads, id: false, hypertable: hypertable_options) do |t|
    t.timestamptz :ts, null: false
    t.text :gem_name, :gem_version, null: false
    t.jsonb :payload
  end

  Download.create_continuous_aggregates
end

# To refresh aggregates:
Download.refresh_aggregates([:hour, :day])  # Refreshes hourly and daily aggregates
# or
Download.refresh_aggregates  # Refreshes all defined timeframes
binding.pry

[jonatas]

I got some mad issue with this name, still not sure how to handle the naming clash. Just renaming this one as seems less prioritized.