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Contents
module Bmg
module Sql
class Processor
class Where < Processor
def initialize(predicate, builder)
super(builder)
@predicate = predicate
end
def on_union(sexpr)
non_falsy = sexpr[2..-1].reject{|expr| falsy?(expr) }
if non_falsy.empty?
apply(sexpr.head_expr)
elsif non_falsy.size == 1
apply(non_falsy.first)
else
[sexpr[0], sexpr[1]] + non_falsy.map{|nf| apply(nf) }
end
end
def on_select_exp(sexpr)
pred = @predicate.rename(sexpr.desaliaser(true))
if sexpr.where_clause
sexpr_p = Predicate.new(sexpr.where_clause.predicate)
sexpr.with_update(:where_clause, [ :where_clause, (sexpr_p & pred).sexpr ])
else
sexpr.with_insert(4, [ :where_clause, pred.sexpr ])
end
end
private
def falsy?(sexpr)
return false unless sexpr.respond_to?(:predicate)
return false if sexpr.predicate.nil?
left = Predicate.new(Predicate::Grammar.sexpr(sexpr.predicate))
right = Predicate.new(Predicate::Grammar.sexpr(@predicate.sexpr))
return (left & right).contradiction?
end
end # class Where
end # class Processor
end # module Sql
end # module Bmg
Version data entries
10 entries across 10 versions & 1 rubygems