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module QueryBuilder
class Parser
class << self
# http://dev.mysql.com/doc/refman/5.1/en/operator-precedence.html
OP_PRECEDENCE = {
:interval => 40,
:binary => 39, :collate => 39,
:"!" => 38,
:"@-" => 37, :"@~" => 37,
:"^" => 36,
:"*" => 35, :"/" => 35, :div => 35, :"%" => 35, :mod => 35,
:"-" => 34, :"+" => 34,
:"<<" => 33, :">>" => 33,
:"&" => 32,
:"|" => 31,
:"=" => 30, :"<=>" => 30, :">=" => 30, :">" => 30, :"<=" => 30, :"<" => 30, :"<>" => 30, :"!=" => 30, :is => 30, :like => 30, :regexp => 30, :in => 30,
:between => 29, :case => 29, :when => 29, :then => 29, :else => 29,
:not => 28,
:"&&" => 27, :and => 27,
:xor => 26,
:"||" => 25, :or => 25,
:":=" => 24,
:relation => 13, :filter => 13,
:scope => 12,
:from => 11, # this is not the same as SQL 'FROM', it's "icons from friends"
:asc => 10, :desc => 10,
:clause => 5,
:clause_and => 4,
:clause_or => 3,
:offset => 2, :paginate => 2, :limit => 2, :order => 2, :group => 2,
:query => 1,
:par_close => 0, :clause_par_close => 0,
:par => -1, :clause_par => -1
}
# group < from < filter < relation < scope
def apply_op(stack, op, change_last = true)
pop_stack(stack, op)
last = stack.last
change_elem = last.last
last[-1] = [op.to_sym, change_elem]
if change_last
stack.push last[-1]
end
stack.last
end
def insert(stack, arg)
# insert [:relation, "..."]
# stack: [[:query]] --> [[:query, [:relation, "..."]], [:relation, "..."]]
pop_stack(stack, arg.first)
last = stack.last
last << arg
stack.push last.last
stack.last
end
def pop_stack(stack, op)
# debug_stack(stack, op)
stack_op = stack.last.first
while OP_PRECEDENCE[op] <= OP_PRECEDENCE[stack_op]
stack.pop
stack_op = stack.last.first
end
end
def debug_stack(stack, msg = '')
puts "======= #{msg} ======="
stack.reverse_each do |s|
puts s.inspect
end
puts "======================"
end
end
end
end
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