122 lines
3.9 KiB
Ruby
122 lines
3.9 KiB
Ruby
# frozen_string_literal: true
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# Include atomic internal id generation scheme for a model
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#
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# This allows us to atomically generate internal ids that are
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# unique within a given scope.
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#
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# For example, let's generate internal ids for Issue per Project:
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# ```
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# class Issue < ApplicationRecord
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# has_internal_id :iid, scope: :project, init: ->(s) { s.project.issues.maximum(:iid) }
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# end
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# ```
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#
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# This generates unique internal ids per project for newly created issues.
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# The generated internal id is saved in the `iid` attribute of `Issue`.
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#
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# This concern uses InternalId records to facilitate atomicity.
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# In the absence of a record for the given scope, one will be created automatically.
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# In this situation, the `init` block is called to calculate the initial value.
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# In the example above, we calculate the maximum `iid` of all issues
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# within the given project.
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#
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# Note that a model may have more than one internal id associated with possibly
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# different scopes.
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module AtomicInternalId
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extend ActiveSupport::Concern
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class_methods do
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def has_internal_id(column, scope:, init:, ensure_if: nil, track_if: nil, presence: true, backfill: false) # rubocop:disable Naming/PredicateName
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# We require init here to retain the ability to recalculate in the absence of a
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# InternalId record (we may delete records in `internal_ids` for example).
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raise "has_internal_id requires a init block, none given." unless init
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raise "has_internal_id needs to be defined on association." unless self.reflect_on_association(scope)
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before_validation :"track_#{scope}_#{column}!", on: :create, if: track_if
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before_validation :"ensure_#{scope}_#{column}!", on: :create, if: ensure_if
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validates column, presence: presence
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define_method("ensure_#{scope}_#{column}!") do
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return if backfill && self.class.where(column => nil).exists?
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scope_value = internal_id_read_scope(scope)
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value = read_attribute(column)
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return value unless scope_value
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if value.nil?
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# We don't have a value yet and use a InternalId record to generate
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# the next value.
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value = InternalId.generate_next(
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self,
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internal_id_scope_attrs(scope),
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internal_id_scope_usage,
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init)
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write_attribute(column, value)
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end
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value
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end
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define_method("track_#{scope}_#{column}!") do
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return unless @internal_id_needs_tracking
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scope_value = internal_id_read_scope(scope)
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return unless scope_value
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value = read_attribute(column)
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if value.present?
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# The value was set externally, e.g. by the user
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# We update the InternalId record to keep track of the greatest value.
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InternalId.track_greatest(
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self,
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internal_id_scope_attrs(scope),
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internal_id_scope_usage,
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value,
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init)
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@internal_id_needs_tracking = false
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end
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end
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define_method("#{column}=") do |value|
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super(value).tap do |v|
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# Indicate the iid was set from externally
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@internal_id_needs_tracking = true
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end
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end
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define_method("reset_#{scope}_#{column}") do
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if value = read_attribute(column)
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did_reset = InternalId.reset(
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self,
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internal_id_scope_attrs(scope),
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internal_id_scope_usage,
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value)
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if did_reset
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write_attribute(column, nil)
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end
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end
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read_attribute(column)
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end
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end
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end
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def internal_id_scope_attrs(scope)
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scope_value = internal_id_read_scope(scope)
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{ scope_value.class.table_name.singularize.to_sym => scope_value } if scope_value
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end
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def internal_id_scope_usage
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self.class.table_name.to_sym
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end
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def internal_id_read_scope(scope)
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association(scope).reader
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end
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end
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