def convertvalref(self, valueref):
"""Convert a Datalog value reference (a literal or a variable) to RA.
Literals are passed through unchanged. Variables are converted"""
if self.match(valueref):
pos = self.position(valueref)
LOG.debug("convertvalref(match) self(%s), valueref(%s), pos(%s)", self, valueref, pos) # noqa
return expression.UnnamedAttributeRef(pos)
else:
# must be a join condition, and the other variable matches
LOG.debug("convertvalref(not) self(%s), valueref(%s)", self, valueref) # noqa
return valueref
def implicitconditions(self):
"""An iterator over implicit selection conditions derived from the
datalog syntax. For example, A(X,X) implies position0 == position1,
and A(X,4) implies position1 == 4"""
# Check for implicit literal equality conditions, like A(X,"foo")
for i, b in enumerate(self.valuerefs):
if isinstance(b, expression.Literal):
posref = expression.UnnamedAttributeRef(i)
yield expression.EQ(posref, b)
# Check for repeated variable conditions, like A(X,X)
N = len(self.valuerefs)
for i, x in enumerate(self.valuerefs):
if isinstance(x, Var):
for j in range(i + 1, N):
y = self.valuerefs[j]
if isinstance(y, Var):
# TODO: probably want to implement __eq__, but it makes
# Var objects unhashable
if x.var == y.var:
leftpos = expression.UnnamedAttributeRef(i)
rightpos = expression.UnnamedAttributeRef(j)
yield expression.EQ(leftpos, rightpos)
def renameIDB(self, plan):
"""Rename the attributes of the plan to match the current rule. Used
when chaining multiple rules."""
term = self
# Do we know the actual scheme? If it's recursive, we don't
# So derive it from the rule head
# Not really satisfied with this.
try:
sch = plan.scheme()
except algebra.RecursionError:
sch = Scheme([make_attr(i, r, term.name)
for i, r in enumerate(term.valuerefs)])
oldscheme = [name for (name, _) in sch]
termscheme = [expr for expr in term.valuerefs]
if len(oldscheme) != len(termscheme):
raise TypeError("Rule with head %s does not match Term %s" % (term.name, term)) # noqa
pairs = zip(termscheme, oldscheme)
# Merge the old and new schemes. Use new where we can.
def choosename(new, old):
if isinstance(new, Var):
# Then use this new var as the column name
return new.var
else:
# It's an implicit selection condition, like R(x,3). In R's
# schema, don't call the column name '3' (new), instead call it
# whatever the column name was in the prior rule where R is the
# head variable R (old).
return old
mappings = [(choosename(new, old), expression.UnnamedAttributeRef(i))
for i, (new, old) in enumerate(pairs)]
# Use an apply operator to implement the renaming
plan = algebra.Apply(mappings, plan)
return plan
def rewrite_node(sexpr):
# Push unboxing into the state variables of distributed aggregates
if isinstance(sexpr, expression.AggregateExpression):
if sexpr.is_decomposable():
ds = sexpr.get_decomposable_state()
lsms = rewrite_statemods(ds.get_local_statemods(), from_args,
base_offsets) # noqa
rsms = rewrite_statemods(ds.get_remote_statemods(), from_args,
base_offsets) # noqa
if lsms or rsms:
sexpr.set_decomposable_state(
expression.DecomposableAggregateState(
ds.get_local_emitters(), lsms,
ds.get_remote_emitters(), rsms,
ds.get_finalizer()))
return sexpr
if not isinstance(sexpr, expression.DottedRef):
return sexpr
elif sexpr.table_alias not in from_args:
raise NoSuchRelationException(sexpr.table_alias)
else:
op = from_args[sexpr.table_alias]
scheme = op.scheme()
debug_info = None
if not sexpr.field:
offset = 0
elif isinstance(sexpr.field, int):
if sexpr.field >= len(scheme):
raise ColumnIndexOutOfBounds(str(sexpr))
offset = sexpr.field
else:
assert isinstance(sexpr.field, basestring)
offset = scheme.getPosition(sexpr.field)
debug_info = sexpr.field
offset += base_offsets[sexpr.table_alias]
return expression.UnnamedAttributeRef(offset, debug_info)
def ascolumnlist(self):
"""Return a columnlist structure suitable for use with Project and
ProjectingJoin. Currently a list of positional attribute references.
May eventually be a scheme itself."""
return [expression.UnnamedAttributeRef(i) for i in xrange(len(self))]
def p_sexpr_index(p):
'sexpr : DOLLAR INTEGER_LITERAL'
p[0] = sexpr.UnnamedAttributeRef(p[2])
def findvar(variable):
var = variable.var
if var not in scheme:
msg = "Head variable %s does not appear in rule body: %s" % (var, self) # noqa
raise SyntaxError(msg)
return expression.UnnamedAttributeRef(scheme.getPosition(var))
