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module Gitlab
module SQL
# Class for building SQL UNION statements.
#
# ORDER BYs are dropped from the relations as the final sort order is not
# guaranteed any way.
#
# Example usage:
#
# union = Gitlab::SQL::Union.new(user.personal_projects, user.projects)
# sql = union.to_sql
#
# Project.where("id IN (#{sql})")
class Union
def initialize(relations)
@relations = relations
end
def to_sql
# Some relations may include placeholders for prepared statements, these
# aren't incremented properly when joining relations together this way.
# By using "unprepared_statements" we remove the usage of placeholders
# (thus fixing this problem), at a slight performance cost.
fragments = ActiveRecord::Base.connection.unprepared_statement do
@relations.map { |rel| rel.reorder(nil).to_sql }.reject(&:blank?)
end
fragments.join("\nUNION\n")
end
end
end
end
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