"""
Converting the 'parse-tree' output of pyparsing to a SPARQL Algebra expression
http://www.w3.org/TR/sparql11-query/#sparqlQuery
"""
from __future__ import print_function
import functools
import operator
import collections
from functools import reduce
from rdflib import Literal, Variable, URIRef, BNode
from rdflib.plugins.sparql.sparql import Prologue, Query
from rdflib.plugins.sparql.parserutils import CompValue, Expr
from rdflib.plugins.sparql.operators import (
and_, TrueFilter, simplify as simplifyFilters)
from rdflib.paths import (
InvPath, AlternativePath, SequencePath, MulPath, NegatedPath)
from pyparsing import ParseResults
# ---------------------------
# Some convenience methods
[docs]def OrderBy(p, expr):
return CompValue('OrderBy', p=p, expr=expr)
[docs]def ToMultiSet(p):
return CompValue('ToMultiSet', p=p)
[docs]def Union(p1, p2):
return CompValue('Union', p1=p1, p2=p2)
[docs]def Join(p1, p2):
return CompValue('Join', p1=p1, p2=p2)
[docs]def Minus(p1, p2):
return CompValue('Minus', p1=p1, p2=p2)
[docs]def Graph(term, graph):
return CompValue('Graph', term=term, p=graph)
[docs]def BGP(triples=None):
return CompValue('BGP', triples=triples or [])
[docs]def LeftJoin(p1, p2, expr):
return CompValue('LeftJoin', p1=p1, p2=p2, expr=expr)
[docs]def Filter(expr, p):
return CompValue('Filter', expr=expr, p=p)
[docs]def Extend(p, expr, var):
return CompValue('Extend', p=p, expr=expr, var=var)
[docs]def Values(res):
return CompValue('values', res=res)
[docs]def Project(p, PV):
return CompValue('Project', p=p, PV=PV)
[docs]def Group(p, expr=None):
return CompValue('Group', p=p, expr=expr)
def _knownTerms(triple, varsknown, varscount):
return (len([x for x in triple if x not in varsknown and
isinstance(x, (Variable, BNode))]),
-sum(varscount.get(x, 0) for x in triple),
not isinstance(triple[2], Literal),
)
[docs]def reorderTriples(l):
"""
Reorder triple patterns so that we execute the
ones with most bindings first
"""
def _addvar(term, varsknown):
if isinstance(term, (Variable, BNode)):
varsknown.add(term)
l = [(None, x) for x in l]
varsknown = set()
varscount = collections.defaultdict(int)
for t in l:
for c in t[1]:
if isinstance(c, (Variable, BNode)):
varscount[c] += 1
i = 0
# Done in steps, sort by number of bound terms
# the top block of patterns with the most bound terms is kept
# the rest is resorted based on the vars bound after the first
# block is evaluated
# we sort by decorate/undecorate, since we need the value of the sort keys
while i < len(l):
l[i:] = sorted((_knownTerms(x[
1], varsknown, varscount), x[1]) for x in l[i:])
t = l[i][0][0] # top block has this many terms bound
j = 0
while i + j < len(l) and l[i + j][0][0] == t:
for c in l[i + j][1]:
_addvar(c, varsknown)
j += 1
i += 1
return [x[1] for x in l]
[docs]def triples(l):
l = reduce(lambda x, y: x + y, l)
if (len(l) % 3) != 0:
raise Exception('these aint triples')
return reorderTriples((l[x], l[x + 1], l[x + 2])
for x in range(0, len(l), 3))
[docs]def translatePName(p, prologue):
"""
Expand prefixed/relative URIs
"""
if isinstance(p, CompValue):
if p.name == 'pname':
return prologue.absolutize(p)
if p.name == 'literal':
return Literal(p.string, lang=p.lang,
datatype=prologue.absolutize(p.datatype))
elif isinstance(p, URIRef):
return prologue.absolutize(p)
[docs]def translatePath(p):
"""
Translate PropertyPath expressions
"""
if isinstance(p, CompValue):
if p.name == 'PathAlternative':
if len(p.part) == 1:
return p.part[0]
else:
return AlternativePath(*p.part)
elif p.name == 'PathSequence':
if len(p.part) == 1:
return p.part[0]
else:
return SequencePath(*p.part)
elif p.name == 'PathElt':
if not p.mod:
return p.part
else:
if isinstance(p.part, list):
if len(p.part) != 1:
raise Exception('Denkfehler!')
return MulPath(p.part[0], p.mod)
else:
return MulPath(p.part, p.mod)
elif p.name == 'PathEltOrInverse':
if isinstance(p.part, list):
if len(p.part) != 1:
raise Exception('Denkfehler!')
return InvPath(p.part[0])
else:
return InvPath(p.part)
elif p.name == 'PathNegatedPropertySet':
if isinstance(p.part, list):
return NegatedPath(AlternativePath(*p.part))
else:
return NegatedPath(p.part)
[docs]def translateExists(e):
"""
Translate the graph pattern used by EXISTS and NOT EXISTS
http://www.w3.org/TR/sparql11-query/#sparqlCollectFilters
"""
def _c(n):
if isinstance(n, CompValue):
if n.name in ('Builtin_EXISTS', 'Builtin_NOTEXISTS'):
n.graph = translateGroupGraphPattern(n.graph)
if n.graph.name == 'Filter':
# filters inside (NOT) EXISTS can see vars bound outside
n.graph.no_isolated_scope = True
e = traverse(e, visitPost=_c)
return e
[docs]def collectAndRemoveFilters(parts):
"""
FILTER expressions apply to the whole group graph pattern in which
they appear.
http://www.w3.org/TR/sparql11-query/#sparqlCollectFilters
"""
filters = []
i = 0
while i < len(parts):
p = parts[i]
if p.name == 'Filter':
filters.append(translateExists(p.expr))
parts.pop(i)
else:
i += 1
if filters:
return and_(*filters)
return None
[docs]def translateGroupOrUnionGraphPattern(graphPattern):
A = None
for g in graphPattern.graph:
g = translateGroupGraphPattern(g)
if not A:
A = g
else:
A = Union(A, g)
return A
[docs]def translateGraphGraphPattern(graphPattern):
return Graph(graphPattern.term,
translateGroupGraphPattern(graphPattern.graph))
[docs]def translateInlineData(graphPattern):
return ToMultiSet(translateValues(graphPattern))
[docs]def translateGroupGraphPattern(graphPattern):
"""
http://www.w3.org/TR/sparql11-query/#convertGraphPattern
"""
if graphPattern.name == 'SubSelect':
return ToMultiSet(translate(graphPattern)[0])
if not graphPattern.part:
graphPattern.part = [] # empty { }
filters = collectAndRemoveFilters(graphPattern.part)
g = []
for p in graphPattern.part:
if p.name == 'TriplesBlock':
# merge adjacent TripleBlocks
if not (g and g[-1].name == 'BGP'):
g.append(BGP())
g[-1]["triples"] += triples(p.triples)
else:
g.append(p)
G = BGP()
for p in g:
if p.name == 'OptionalGraphPattern':
A = translateGroupGraphPattern(p.graph)
if A.name == 'Filter':
G = LeftJoin(G, A.p, A.expr)
else:
G = LeftJoin(G, A, TrueFilter)
elif p.name == 'MinusGraphPattern':
G = Minus(p1=G, p2=translateGroupGraphPattern(p.graph))
elif p.name == 'GroupOrUnionGraphPattern':
G = Join(p1=G, p2=translateGroupOrUnionGraphPattern(p))
elif p.name == 'GraphGraphPattern':
G = Join(p1=G, p2=translateGraphGraphPattern(p))
elif p.name == 'InlineData':
G = Join(p1=G, p2=translateInlineData(p))
elif p.name == 'ServiceGraphPattern':
G = Join(p1=G, p2=p)
elif p.name in ('BGP', 'Extend'):
G = Join(p1=G, p2=p)
elif p.name == 'Bind':
G = Extend(G, p.expr, p.var)
else:
raise Exception('Unknown part in GroupGraphPattern: %s - %s' %
(type(p), p.name))
if filters:
G = Filter(expr=filters, p=G)
return G
[docs]class StopTraversal(Exception):
[docs] def __init__(self, rv):
self.rv = rv
def _traverse(e, visitPre=lambda n: None, visitPost=lambda n: None):
"""
Traverse a parse-tree, visit each node
if visit functions return a value, replace current node
"""
_e = visitPre(e)
if _e is not None:
return _e
if e is None:
return None
if isinstance(e, (list, ParseResults)):
return [_traverse(x, visitPre, visitPost) for x in e]
elif isinstance(e, tuple):
return tuple([_traverse(x, visitPre, visitPost) for x in e])
elif isinstance(e, CompValue):
for k, val in e.items():
e[k] = _traverse(val, visitPre, visitPost)
_e = visitPost(e)
if _e is not None:
return _e
return e
def _traverseAgg(e, visitor=lambda n, v: None):
"""
Traverse a parse-tree, visit each node
if visit functions return a value, replace current node
"""
res = []
if isinstance(e, (list, ParseResults, tuple)):
res = [_traverseAgg(x, visitor) for x in e]
elif isinstance(e, CompValue):
for k, val in e.items():
if val is not None:
res.append(_traverseAgg(val, visitor))
return visitor(e, res)
[docs]def traverse(
tree, visitPre=lambda n: None,
visitPost=lambda n: None, complete=None):
"""
Traverse tree, visit each node with visit function
visit function may raise StopTraversal to stop traversal
if complete!=None, it is returned on complete traversal,
otherwise the transformed tree is returned
"""
try:
r = _traverse(tree, visitPre, visitPost)
if complete is not None:
return complete
return r
except StopTraversal as st:
return st.rv
def _hasAggregate(x):
"""
Traverse parse(sub)Tree
return true if any aggregates are used
"""
if isinstance(x, CompValue):
if x.name.startswith('Aggregate_'):
raise StopTraversal(True)
def _aggs(e, A):
"""
Collect Aggregates in A
replaces aggregates with variable references
"""
# TODO: nested Aggregates?
if isinstance(e, CompValue) and e.name.startswith('Aggregate_'):
A.append(e)
aggvar = Variable('__agg_%d__' % len(A))
e["res"] = aggvar
return aggvar
def _findVars(x, res):
"""
Find all variables in a tree
"""
if isinstance(x, Variable):
res.add(x)
if isinstance(x, CompValue):
if x.name == "Bind":
res.add(x.var)
return x # stop recursion and finding vars in the expr
elif x.name == 'SubSelect':
if x.projection:
res.update(v.var or v.evar for v in x.projection)
return x
def _addVars(x, children):
"""
find which variables may be bound by this part of the query
"""
if isinstance(x, Variable):
return set([x])
elif isinstance(x, CompValue):
if x.name == "RelationalExpression":
x["_vars"] = set()
elif x.name == "Extend":
# vars only used in the expr for a bind should not be included
x["_vars"] = reduce(operator.or_, [child for child,
part in zip(children, x) if part != 'expr'], set())
else:
x["_vars"] = set(reduce(operator.or_, children, set()))
if x.name == 'SubSelect':
if x.projection:
s = set(v.var or v.evar for v in x.projection)
else:
s = set()
return s
return x["_vars"]
return reduce(operator.or_, children, set())
def _sample(e, v=None):
"""
For each unaggregated variable V in expr
Replace V with Sample(V)
"""
if isinstance(e, CompValue) and e.name.startswith("Aggregate_"):
return e # do not replace vars in aggregates
if isinstance(e, Variable) and v != e:
return CompValue('Aggregate_Sample', vars=e)
def _simplifyFilters(e):
if isinstance(e, Expr):
return simplifyFilters(e)
[docs]def translateAggregates(q, M):
E = []
A = []
# collect/replace aggs in :
# select expr as ?var
if q.projection:
for v in q.projection:
if v.evar:
v.expr = traverse(v.expr, functools.partial(_sample, v=v.evar))
v.expr = traverse(v.expr, functools.partial(_aggs, A=A))
# having clause
if traverse(q.having, _hasAggregate, complete=False):
q.having = traverse(q.having, _sample)
traverse(q.having, functools.partial(_aggs, A=A))
# order by
if traverse(q.orderby, _hasAggregate, complete=False):
q.orderby = traverse(q.orderby, _sample)
traverse(q.orderby, functools.partial(_aggs, A=A))
# sample all other select vars
# TODO: only allowed for vars in group-by?
if q.projection:
for v in q.projection:
if v.var:
rv = Variable('__agg_%d__' % (len(A) + 1))
A.append(CompValue('Aggregate_Sample', vars=v.var, res=rv))
E.append((rv, v.var))
return CompValue('AggregateJoin', A=A, p=M), E
[docs]def translateValues(v):
# if len(v.var)!=len(v.value):
# raise Exception("Unmatched vars and values in ValueClause: "+str(v))
res = []
if not v.var:
return res
if not v.value:
return res
if not isinstance(v.value[0], list):
for val in v.value:
res.append({v.var[0]: val})
else:
for vals in v.value:
res.append(dict(zip(v.var, vals)))
return Values(res)
[docs]def translate(q):
"""
http://www.w3.org/TR/sparql11-query/#convertSolMod
"""
_traverse(q, _simplifyFilters)
q.where = traverse(q.where, visitPost=translatePath)
# TODO: Var scope test
VS = set()
traverse(q.where, functools.partial(_findVars, res=VS))
# all query types have a where part
M = translateGroupGraphPattern(q.where)
aggregate = False
if q.groupby:
conditions = []
# convert "GROUP BY (?expr as ?var)" to an Extend
for c in q.groupby.condition:
if isinstance(c, CompValue) and c.name == 'GroupAs':
M = Extend(M, c.expr, c.var)
c = c.var
conditions.append(c)
M = Group(p=M, expr=conditions)
aggregate = True
elif traverse(q.having, _hasAggregate, complete=False) or \
traverse(q.orderby, _hasAggregate, complete=False) or \
any(traverse(x.expr, _hasAggregate, complete=False)
for x in q.projection or [] if x.evar):
# if any aggregate is used, implicit group by
M = Group(p=M)
aggregate = True
if aggregate:
M, E = translateAggregates(q, M)
else:
E = []
# HAVING
if q.having:
M = Filter(expr=and_(*q.having.condition), p=M)
# VALUES
if q.valuesClause:
M = Join(p1=M, p2=ToMultiSet(translateValues(q.valuesClause)))
if not q.projection:
# select *
PV = list(VS)
else:
PV = list()
for v in q.projection:
if v.var:
if v not in PV:
PV.append(v.var)
elif v.evar:
if v not in PV:
PV.append(v.evar)
E.append((v.expr, v.evar))
else:
raise Exception("I expected a var or evar here!")
for e, v in E:
M = Extend(M, e, v)
# ORDER BY
if q.orderby:
M = OrderBy(M, [CompValue('OrderCondition', expr=c.expr,
order=c.order) for c in q.orderby.condition])
# PROJECT
M = Project(M, PV)
if q.modifier:
if q.modifier == 'DISTINCT':
M = CompValue('Distinct', p=M)
elif q.modifier == 'REDUCED':
M = CompValue('Reduced', p=M)
if q.limitoffset:
offset = 0
if q.limitoffset.offset is not None:
offset = q.limitoffset.offset.toPython()
if q.limitoffset.limit is not None:
M = CompValue('Slice', p=M, start=offset,
length=q.limitoffset.limit.toPython())
else:
M = CompValue('Slice', p=M, start=offset)
return M, PV
[docs]def simplify(n):
"""Remove joins to empty BGPs"""
if isinstance(n, CompValue):
if n.name == 'Join':
if n.p1.name == 'BGP' and len(n.p1.triples) == 0:
return n.p2
if n.p2.name == 'BGP' and len(n.p2.triples) == 0:
return n.p1
elif n.name == 'BGP':
n["triples"] = reorderTriples(n.triples)
return n
[docs]def analyse(n, children):
"""
Some things can be lazily joined.
This propegates whether they can up the tree
and sets lazy flags for all joins
"""
if isinstance(n, CompValue):
if n.name == 'Join':
n["lazy"] = all(children)
return False
elif n.name in ('Slice', 'Distinct'):
return False
else:
return all(children)
else:
return True
[docs]def translatePrologue(p, base, initNs=None, prologue=None):
if prologue is None:
prologue = Prologue()
prologue.base = ""
if base:
prologue.base = base
if initNs:
for k, v in initNs.items():
prologue.bind(k, v)
for x in p:
if x.name == 'Base':
prologue.base = x.iri
elif x.name == 'PrefixDecl':
prologue.bind(x.prefix, prologue.absolutize(x.iri))
return prologue
[docs]def translateQuads(quads):
if quads.triples:
alltriples = triples(quads.triples)
else:
alltriples = []
allquads = collections.defaultdict(list)
if quads.quadsNotTriples:
for q in quads.quadsNotTriples:
if q.triples:
allquads[q.term] += triples(q.triples)
return alltriples, allquads
[docs]def translateUpdate1(u, prologue):
if u.name in ('Load', 'Clear', 'Drop', 'Create'):
pass # no translation needed
elif u.name in ('Add', 'Move', 'Copy'):
pass
elif u.name in ('InsertData', 'DeleteData', 'DeleteWhere'):
t, q = translateQuads(u.quads)
u["quads"] = q
u["triples"] = t
if u.name in ('DeleteWhere', 'DeleteData'):
pass # TODO: check for bnodes in triples
elif u.name == 'Modify':
if u.delete:
u.delete["triples"], u.delete[
"quads"] = translateQuads(u.delete.quads)
if u.insert:
u.insert["triples"], u.insert[
"quads"] = translateQuads(u.insert.quads)
u["where"] = translateGroupGraphPattern(u.where)
else:
raise Exception('Unknown type of update operation: %s' % u)
u.prologue = prologue
return u
[docs]def translateUpdate(q, base=None, initNs=None):
"""
Returns a list of SPARQL Update Algebra expressions
"""
res = []
prologue = None
if not q.request:
return res
for p, u in zip(q.prologue, q.request):
prologue = translatePrologue(p, base, initNs, prologue)
# absolutize/resolve prefixes
u = traverse(
u, visitPost=functools.partial(translatePName, prologue=prologue))
u = _traverse(u, _simplifyFilters)
u = traverse(u, visitPost=translatePath)
res.append(translateUpdate1(u, prologue))
return res
[docs]def translateQuery(q, base=None, initNs=None):
"""
Translate a query-parsetree to a SPARQL Algebra Expression
Return a rdflib.plugins.sparql.sparql.Query object
"""
# We get in: (prologue, query)
prologue = translatePrologue(q[0], base, initNs)
# absolutize/resolve prefixes
q[1] = traverse(
q[1], visitPost=functools.partial(translatePName, prologue=prologue))
P, PV = translate(q[1])
datasetClause = q[1].datasetClause
if q[1].name == 'ConstructQuery':
template = triples(q[1].template) if q[1].template else None
res = CompValue(q[1].name, p=P,
template=template,
datasetClause=datasetClause)
else:
res = CompValue(q[1].name, p=P, datasetClause=datasetClause, PV=PV)
res = traverse(res, visitPost=simplify)
_traverseAgg(res, visitor=analyse)
_traverseAgg(res, _addVars)
return Query(prologue, res)
[docs]def pprintAlgebra(q):
def pp(p, ind=" "):
# if isinstance(p, list):
# print "[ "
# for x in p: pp(x,ind)
# print "%s ]"%ind
# return
if not isinstance(p, CompValue):
print(p)
return
print("%s(" % (p.name, ))
for k in p:
print("%s%s =" % (ind, k,), end=' ')
pp(p[k], ind + " ")
print("%s)" % ind)
try:
pp(q.algebra)
except AttributeError:
# it's update, just a list
for x in q:
pp(x)
if __name__ == '__main__':
import sys
from rdflib.plugins.sparql import parser
import os.path
if os.path.exists(sys.argv[1]):
q = file(sys.argv[1])
else:
q = sys.argv[1]
pq = parser.parseQuery(q)
print(pq)
tq = translateQuery(pq)
pprintAlgebra(tq)
