2010-09-23 14:45:29 -04:00
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module Arel
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module Visitors
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class PostgreSQL < Arel::Visitors::ToSql
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2010-09-23 16:07:48 -04:00
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private
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def visit_Arel_Nodes_SelectStatement o
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if !o.orders.empty? && using_distinct_on?(o)
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subquery = o.dup
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subquery.orders = []
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subquery.limit = nil
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subquery.offset = nil
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sql = super(subquery)
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[
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"SELECT * FROM (#{sql}) AS id_list",
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2010-09-23 16:37:03 -04:00
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"ORDER BY #{aliased_orders(o.orders).join(', ')}",
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2010-09-23 16:07:48 -04:00
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("LIMIT #{o.limit}" if o.limit),
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(visit(o.offset) if o.offset),
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].compact.join ' '
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else
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super
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end
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end
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def using_distinct_on?(o)
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o.cores.any? do |core|
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core.projections.any? do |projection|
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/DISTINCT ON/ === projection
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end
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end
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end
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2010-09-23 16:37:03 -04:00
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def aliased_orders orders
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#orders = o.orders.map { |x| visit x }.join(', ').split(',')
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2010-09-23 16:48:09 -04:00
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list = []
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orders.each_with_index do |o,i|
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list <<
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[
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"id_list.alias_#{i}",
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(o.index(/desc/i) && 'DESC')
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].compact.join(' ')
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end
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list
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2010-09-23 16:37:03 -04:00
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end
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2010-09-23 14:45:29 -04:00
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end
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end
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end
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