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module Arel
class Where < Compound
def eval
unoperated_rows.select { |row| predicate.eval(row) }
end
end
class Order < Compound
def eval
unoperated_rows.sort do |row1, row2|
ordering = orderings.detect { |o| o.eval(row1, row2) != 0 } || orderings.last
ordering.eval(row1, row2)
end
end
end
class Project < Compound
def eval
unoperated_rows.collect { |r| r.slice(*projections) }
end
end
class Take < Compound
def eval
unoperated_rows[0, taken]
end
end
class Skip < Compound
def eval
unoperated_rows[skipped..-1]
end
end
class Group < Compound
def eval
raise NotImplementedError
end
end
class Alias < Compound
def eval
unoperated_rows
end
end
class Join < Relation
def eval
result = []
relation1.eval.each do |row1|
relation2.eval.each do |row2|
combined_row = row1.combine(row2, self)
if predicates.all? { |p| p.eval(combined_row) }
result << combined_row
end
end
end
result
end
end
end
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