public static Collection<Quad> collectQuads(Op op, Collection<Quad> result) {
if (op instanceof OpLeftJoin) {
OpLeftJoin x = (OpLeftJoin) op;
collectQuads(x.getLeft(), result);
collectQuads(x.getRight(), result);
} else if (op instanceof OpFilter) {
OpFilter x = (OpFilter) op;
collectQuads(x.getSubOp(), result);
} else if (op instanceof OpJoin) {
OpJoin x = (OpJoin) op;
collectQuads(x.getLeft(), result);
collectQuads(x.getRight(), result);
} else if (op instanceof OpUnion) {
System.out.println(
"Warning: Collecting expressions from unions. Since the same vars may appear within different (parts of) unions, it may be ambiguous to which part the expression refers.");
OpUnion x = (OpUnion) op;
collectQuads(x.getLeft(), result);
collectQuads(x.getRight(), result);
} else if (op instanceof OpQuadPattern) {
OpQuadPattern x = (OpQuadPattern) op;
result.addAll(x.getPattern().getList());
} else if (op instanceof OpSequence) {
OpSequence x = (OpSequence) op;
for (Op element : x.getElements()) {
collectQuads(element, result);
}
} else {
throw new NotImplementedException("Encountered class: " + op);
}
return result;
}
private static Op transformFilterQuadPattern(
ExprList exprs, Set<Var> patternVarsScope, Node graphNode, BasicPattern pattern) {
// Any filters that depend on no variables.
Op op = insertAnyFilter(exprs, patternVarsScope, null);
if (Var.isVar(graphNode)) {
// Add in the graph node of the quad block.
// It's picked up after the first triple is processed.
VarUtils.addVar(patternVarsScope, Var.alloc(graphNode));
}
for (Triple triple : pattern) {
OpQuadPattern opQuad = getQuads(op);
if (opQuad == null) {
opQuad = new OpQuadPattern(graphNode, new BasicPattern());
op = OpSequence.create(op, opQuad);
}
opQuad.getBasicPattern().add(triple);
// Update variables in scope.
VarUtils.addVarsFromTriple(patternVarsScope, triple);
// Attempt to place any filters
op = insertAnyFilter(exprs, patternVarsScope, op);
}
return op;
}
@Override
public Op transform(OpQuadPattern quadPattern) {
Node gNode = quadPattern.getGraphNode();
Node g = substitute(gNode, binding);
BasicPattern triples = new BasicPattern();
for (Triple triple : quadPattern.getBasicPattern()) {
Node s = substitute(triple.getSubject(), binding);
Node p = substitute(triple.getPredicate(), binding);
Node o = substitute(triple.getObject(), binding);
Triple t = new Triple(s, p, o);
triples.add(t);
}
// Pure quading.
// for ( Iterator iter = quadPattern.getQuads().iterator() ;
// iter.hasNext() ; )
// {
// Quad quad = (Quad)iter.next() ;
// if ( ! quad.getGraph().equals(gNode) )
// throw new
// ARQInternalErrorException("Internal error: quads block is not uniform over the graph node")
// ;
// Node s = substitute(quad.getSubject(), binding) ;
// Node p = substitute(quad.getPredicate(), binding) ;
// Node o = substitute(quad.getObject(), binding) ;
// Triple t = new Triple(s, p, o) ;
// triples.add(t) ;
// }
return new OpQuadPattern(g, triples);
}
public void visit(OpQuadPattern quadPattern) {
System.out.println(quadPattern.toString());
}
private static Op transformFilterQuadPattern(
ExprList exprs, Set<Var> patternVarsScope, OpQuadPattern pattern) {
return transformFilterQuadPattern(
exprs, patternVarsScope, pattern.getGraphNode(), pattern.getBasicPattern());
}