def _check_fusion(self, root):
roots = root.table._root_tables()
validator = ExprValidator([root.table])
fused_exprs = []
can_fuse = False
for val in self.clean_exprs:
# XXX
lifted_val = substitute_parents(val)
# a * projection
if (isinstance(val, ir.TableExpr) and
(self.parent.op().is_ancestor(val) or
# gross we share the same table root. Better way to
# detect?
len(roots) == 1 and val._root_tables()[0] is roots[0])):
can_fuse = True
fused_exprs.extend(root.selections)
elif validator.validate(lifted_val):
fused_exprs.append(lifted_val)
elif not validator.validate(val):
can_fuse = False
break
else:
fused_exprs.append(val)
if can_fuse:
return ops.Projection(root.table, fused_exprs)
else:
return None
def get_result(self):
roots = self.parent_roots
if len(roots) == 1 and isinstance(roots[0], ops.Projection):
fused_op = self._check_fusion(roots[0])
if fused_op is not None:
return fused_op
return ops.Projection(self.parent, self.clean_exprs)
def _lift_Projection(self, expr, block=None):
if block is None:
block = self.block_projection
op = expr.op()
if block:
# GH #549: dig no further
return expr
else:
lifted_table, unch = self._lift_arg(op.table, block=True)
lifted_selections, unch_sel = self._lift_arg(op.selections, block=True)
unchanged = unch and unch_sel
if not unchanged:
lifted_projection = ops.Projection(lifted_table, lifted_selections)
result = ir.TableExpr(lifted_projection)
else:
result = expr
return result