88 lines
2.8 KiB
Ruby
88 lines
2.8 KiB
Ruby
# frozen_string_literal: true
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module Gitlab
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module SQL
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# Class for building SQL set operator statements (UNION, INTERSECT, and
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# EXCEPT).
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#
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# ORDER BYs are dropped from the relations as the final sort order is not
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# guaranteed any way.
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#
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# remove_order: false option can be used in special cases where the
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# ORDER BY is necessary for the query.
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#
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# Example usage:
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#
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# union = Gitlab::SQL::Union.new([user.personal_projects, user.projects])
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# sql = union.to_sql
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#
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# Project.where("id IN (#{sql})")
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class SetOperator
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def initialize(relations, remove_duplicates: true, remove_order: true)
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verify_select_values!(relations) if Rails.env.test? || Rails.env.development?
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@relations = relations
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@remove_duplicates = remove_duplicates
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@remove_order = remove_order
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end
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def self.operator_keyword
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raise NotImplementedError
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end
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def to_sql
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# Some relations may include placeholders for prepared statements, these
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# aren't incremented properly when joining relations together this way.
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# By using "unprepared_statements" we remove the usage of placeholders
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# (thus fixing this problem), at a slight performance cost.
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fragments = ApplicationRecord.connection.unprepared_statement do
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relations.map do |rel|
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remove_order ? rel.reorder(nil).to_sql : rel.to_sql
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end.reject(&:blank?)
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end
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if fragments.any?
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"(" + fragments.join(")\n#{operator_keyword_fragment}\n(") + ")"
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else
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'NULL'
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end
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end
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# UNION [ALL] | INTERSECT [ALL] | EXCEPT [ALL]
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def operator_keyword_fragment
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remove_duplicates ? self.class.operator_keyword : "#{self.class.operator_keyword} ALL"
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end
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private
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attr_reader :relations, :remove_duplicates, :remove_order
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def verify_select_values!(relations)
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all_select_values = relations.map do |relation|
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if relation.respond_to?(:select_values)
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relation.select_values
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else
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relation.projections # Handle Arel based subqueries
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end
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end
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unless all_select_values.map(&:size).uniq.one?
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relation_select_sizes = all_select_values.map.with_index do |select_values, index|
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if select_values.empty?
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"Relation ##{index}: *, all columns"
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else
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"Relation ##{index}: #{select_values.size} select values"
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end
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end
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exception_text = <<~EOF
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Relations with uneven select values were passed. The UNION query could break when the underlying table changes (add or remove columns).
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#{relation_select_sizes.join("\n")}
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EOF
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raise(exception_text)
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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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