232 lines
8.6 KiB
Ruby
232 lines
8.6 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module Pagination
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module Keyset
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# This class transforms the `order()` values from an Activerecord scope into a
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# Gitlab::Pagination::Keyset::Order instance so the query later can be used in
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# keyset pagination.
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#
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# Return values:
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# [transformed_scope, true] # true indicates that the new scope was successfully built
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# [orginal_scope, false] # false indicates that the order values are not supported in this class
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class SimpleOrderBuilder
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NULLS_ORDER_REGEX = /(?<column_name>.*) (?<direction>\bASC\b|\bDESC\b) (?<nullable>\bNULLS LAST\b|\bNULLS FIRST\b)/.freeze
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def self.build(scope)
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new(scope: scope).build
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end
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def initialize(scope:)
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@scope = scope
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# We need to run 'compact' because 'nil' is not removed from order_values
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# in some cases due to the use of 'default_scope'.
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@order_values = scope.order_values.compact
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@model_class = scope.model
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@arel_table = @model_class.arel_table
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@primary_key = @model_class.primary_key
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end
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def build
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order = if order_values.empty?
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primary_key_descending_order
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elsif Gitlab::Pagination::Keyset::Order.keyset_aware?(scope)
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Gitlab::Pagination::Keyset::Order.extract_keyset_order_object(scope)
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# Ordered by a primary key. Ex. 'ORDER BY id'.
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elsif ordered_by_primary_key?
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primary_key_order
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# Ordered by one non-primary table column. Ex. 'ORDER BY created_at'.
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elsif ordered_by_other_column?
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column_with_tie_breaker_order
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# Ordered by two table columns with the last column as a tie breaker. Ex. 'ORDER BY created, id ASC'.
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elsif ordered_by_other_column_with_tie_breaker?
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tie_breaker_attribute = order_values.second
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tie_breaker_column_order = Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
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attribute_name: model_class.primary_key,
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order_expression: tie_breaker_attribute
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)
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column_with_tie_breaker_order(tie_breaker_column_order)
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end
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order ? [scope.reorder!(order), true] : [scope, false] # [scope, success]
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end
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private
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attr_reader :scope, :order_values, :model_class, :arel_table, :primary_key
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def table_column?(name)
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model_class.column_names.include?(name.to_s)
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end
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def primary_key?(attribute)
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arel_table[primary_key].to_s == attribute.to_s
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end
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def lower_named_function?(attribute)
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attribute.is_a?(Arel::Nodes::NamedFunction) && attribute.name&.downcase == 'lower'
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end
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def arel_nulls?(order_value)
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return unless order_value.is_a?(Arel::Nodes::NullsLast) || order_value.is_a?(Arel::Nodes::NullsFirst)
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column_name = order_value.try(:expr).try(:expr).try(:name)
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table_column?(column_name)
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end
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def supported_column?(order_value)
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return true if arel_nulls?(order_value)
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attribute = order_value.try(:expr)
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return unless attribute
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if lower_named_function?(attribute)
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attribute.expressions.one? && attribute.expressions.first.respond_to?(:name) && table_column?(attribute.expressions.first.name)
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else
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attribute.respond_to?(:name) && table_column?(attribute.name)
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end
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end
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# This method converts the first order value to a corresponding arel expression
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# if the order value uses either NULLS LAST or NULLS FIRST ordering in raw SQL.
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#
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# TODO: https://gitlab.com/gitlab-org/gitlab/-/issues/356644
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# We should stop matching raw literals once we switch to using the Arel methods.
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def convert_raw_nulls_order!
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order_value = order_values.first
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return unless order_value.is_a?(Arel::Nodes::SqlLiteral)
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# Detect NULLS LAST or NULLS FIRST ordering by looking at the raw SQL string.
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if matches = order_value.match(NULLS_ORDER_REGEX)
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return unless table_column?(matches[:column_name])
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column_attribute = arel_table[matches[:column_name]]
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direction = matches[:direction].downcase.to_sym
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nullable = matches[:nullable].downcase.parameterize(separator: '_').to_sym
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# Build an arel order expression for NULLS ordering.
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order = direction == :desc ? column_attribute.desc : column_attribute.asc
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arel_order_expression = nullable == :nulls_first ? order.nulls_first : order.nulls_last
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order_values[0] = arel_order_expression
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end
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end
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def nullability(order_value, attribute_name)
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nullable = model_class.columns.find { |column| column.name == attribute_name }.null
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if nullable && order_value.is_a?(Arel::Nodes::Ascending)
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:nulls_last
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elsif nullable && order_value.is_a?(Arel::Nodes::Descending)
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:nulls_first
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else
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:not_nullable
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end
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end
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def primary_key_descending_order
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Gitlab::Pagination::Keyset::Order.build([
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Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
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attribute_name: model_class.primary_key,
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order_expression: arel_table[primary_key].desc
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)
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])
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end
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def primary_key_order
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Gitlab::Pagination::Keyset::Order.build([
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Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
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attribute_name: model_class.primary_key,
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order_expression: order_values.first
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)
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])
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end
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def column_with_tie_breaker_order(tie_breaker_column_order = default_tie_breaker_column_order)
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Gitlab::Pagination::Keyset::Order.build([
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column(order_values.first),
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tie_breaker_column_order
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])
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end
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def column(order_value)
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return nulls_order_column(order_value) if arel_nulls?(order_value)
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return lower_named_function_column(order_value) if lower_named_function?(order_value.expr)
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attribute_name = order_value.expr.name
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Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
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attribute_name: attribute_name,
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order_expression: order_value,
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nullable: nullability(order_value, attribute_name),
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distinct: false
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)
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end
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def nulls_order_column(order_value)
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attribute = order_value.expr.expr
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Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
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attribute_name: attribute.name,
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column_expression: attribute,
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order_expression: order_value,
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reversed_order_expression: order_value.reverse,
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order_direction: order_value.expr.direction,
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nullable: order_value.is_a?(Arel::Nodes::NullsLast) ? :nulls_last : :nulls_first,
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distinct: false
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)
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end
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def lower_named_function_column(order_value)
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attribute_name = order_value.expr.expressions.first.name
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Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
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attribute_name: attribute_name,
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column_expression: Arel::Nodes::NamedFunction.new("LOWER", [model_class.arel_table[attribute_name]]),
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order_expression: order_value,
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nullable: nullability(order_value, attribute_name),
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distinct: false
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)
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end
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def ordered_by_primary_key?
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return unless order_values.one?
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attribute = order_values.first.try(:expr)
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attribute && primary_key?(attribute)
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end
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def ordered_by_other_column?
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return unless order_values.one?
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convert_raw_nulls_order!
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supported_column?(order_values.first)
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end
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def ordered_by_other_column_with_tie_breaker?
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return unless order_values.size == 2
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convert_raw_nulls_order!
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return unless supported_column?(order_values.first)
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tie_breaker_attribute = order_values.second.try(:expr)
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tie_breaker_attribute && primary_key?(tie_breaker_attribute)
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end
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def default_tie_breaker_column_order
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Gitlab::Pagination::Keyset::ColumnOrderDefinition.new(
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attribute_name: model_class.primary_key,
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order_expression: arel_table[primary_key].desc
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)
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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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