class Arel::Nodes::Node

Abstract base class for all AST nodes
##

def and(right)

Factory method to create an Nodes::And node.
## 
def and(right)
  Nodes::And.new [self, right]
end

def equality?; false; end 

def equality?; false; end

def fetch_attribute 

def fetch_attribute
end

def invert 

def invert
  Arel::Nodes::Not.new(self)
end

def not

the caller as a child.
Factory method to create a Nodes::Not node that has the recipient of
## 
def not
  Nodes::Not.new self
end

def or(right)

node as a child.
Factory method to create a Nodes::Grouping node that has an Nodes::Or
## 
def or(right)
  Nodes::Grouping.new Nodes::Or.new(self, right)
end

def to_sql(engine = Table.engine)

Maybe we should just use `Table.engine`? :'(

can find a node that has a "relation" member.
to_sql on non-head nodes. This forces us to walk the AST until we
FIXME: this method should go away. I don't like people calling 
def to_sql(engine = Table.engine)
  collector = Arel::Collectors::SQLString.new
  collector = engine.connection.visitor.accept self, collector
  collector.value
end