57 lines
1.7 KiB
Ruby
57 lines
1.7 KiB
Ruby
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# 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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class Pager
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attr_reader :request
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def initialize(request)
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@request = request
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end
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def paginate(relation)
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# Validate assumption: The last two columns must match the page order_by
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validate_order!(relation)
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# This performs the database query and retrieves records
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# We retrieve one record more to check if we have data beyond this page
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all_records = relation.limit(page.per_page + 1).to_a # rubocop: disable CodeReuse/ActiveRecord
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records_for_page = all_records.first(page.per_page)
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# If we retrieved more records than belong on this page,
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# we know there's a next page
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there_is_more = all_records.size > records_for_page.size
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apply_headers(records_for_page.last, there_is_more)
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records_for_page
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end
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private
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def apply_headers(last_record_in_page, there_is_more)
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end_reached = last_record_in_page.nil? || !there_is_more
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lower_bounds = last_record_in_page&.slice(page.order_by.keys)
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next_page = page.next(lower_bounds, end_reached)
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request.apply_headers(next_page)
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end
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def page
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@page ||= request.page
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end
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def validate_order!(rel)
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present_order = rel.order_values.map { |val| [val.expr.name.to_sym, val.direction] }.last(2).to_h
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unless page.order_by == present_order
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raise ArgumentError, "Page's order_by does not match the relation's order: #{present_order} vs #{page.order_by}"
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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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end
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