/**
* Resolve a constraint against an RDF/XML document.
*
* <p>Resolution is by filtration of a URL stream, and thus very slow.
*/
public Resolution resolve(Constraint constraint) throws QueryException {
if (logger.isDebugEnabled()) {
logger.debug("Resolve " + constraint);
}
// Validate "constraint" parameter
if (constraint == null) {
throw new IllegalArgumentException("Null \"constraint\" parameter");
}
if (!(constraint.getModel() instanceof LocalNode)) {
if (logger.isDebugEnabled()) logger.debug("Ignoring solutions for " + constraint);
return new EmptyResolution(constraint, false);
}
if (!(constraint.getElement(1) instanceof LocalNode)
|| !(constraint.getElement(2) instanceof LocalNode)) {
throw new QueryException(
"Prefix resolver can only be used for fixed prefixes: " + constraint);
}
try {
long property = ((LocalNode) constraint.getElement(1)).getValue();
LocalNode object = (LocalNode) constraint.getElement(2);
Node prefixNode = resolverSession.globalize(object.getValue());
// check the constraint for consistency
if ((property != mulgaraPrefix && property != mulgaraStringPrefix)
|| !(prefixNode instanceof Literal || prefixNode instanceof URIReference)) {
logger.debug("property = " + property + ", mulgaraPrefix = " + mulgaraPrefix);
logger.debug("element(2): " + prefixNode + " [" + prefixNode.getClass().getName() + "]");
throw new QueryException(
"Prefix resolver can only be used for prefix constraints: " + constraint);
}
if (logger.isDebugEnabled()) {
logger.debug(
"Evaluating " + constraint.getElement(0) + " has prefix " + constraint.getElement(2));
}
ConstraintElement node = constraint.getElement(0);
assert node != null;
Tuples tuples;
if (node instanceof Variable) {
// convert the prefix into a string pool object
SPObjectFactory spoFact = SPObjectFactoryImpl.getInstance();
SPObject startPrefixObj = getStartObject(spoFact, prefixNode, property);
SPObject endPrefixObj = getEndObject(spoFact, prefixNode, property);
// get the extents of the prefix from the string pool
tuples = resolverSession.findStringPoolRange(startPrefixObj, true, endPrefixObj, false);
assert tuples != null;
// rename variables away from subject, predicate and object
tuples.renameVariables(constraint);
long resultSize;
try {
// Get the size of the final result.
resultSize = tuples.getRowCount();
} catch (TuplesException e) {
throw new QueryException("Unable to build result", e);
}
if (logger.isDebugEnabled()) {
try {
logger.debug(
"tuples size = " + tuples.getRowCount() + " (should be " + resultSize + ")");
} catch (TuplesException e) {
logger.debug("Error getting the length of the tuples object");
}
}
return new TuplesWrapperResolution(tuples, constraint);
} else { // if (node instanceof Variable)
// node must therefore be an instanceof LocalNode
// we can shortcut the process here
assert node instanceof LocalNode;
LocalNode n = (LocalNode) node;
// get the node out of the string pool
SPObject spo = resolverSession.findStringPoolObject(n.getValue());
// check that the node exists
if (spo == null) {
tuples = TuplesOperations.empty();
} else {
// see if the node starts with the required prefix
String prefix;
// extract the string from the literal
if (prefixNode instanceof Literal) {
prefix = ((Literal) prefixNode).getLexicalForm();
} else {
prefix = ((URIReference) prefixNode).getURI().toString();
}
if (spo.getLexicalForm().startsWith(prefix)) {
tuples = TuplesOperations.unconstrained();
} else {
tuples = TuplesOperations.empty();
}
}
}
// convert the tuples to a resolution
return new TuplesWrapperResolution(tuples, constraint);
} catch (GlobalizeException ge) {
throw new QueryException("Couldn't convert internal data into a string", ge);
} catch (StringPoolException e) {
throw new QueryException("Couldn't query constraint", e);
}
}
/**
* @see
* org.mulgara.store.stringpool.AbstractSPObject#numericalCompare(org.mulgara.store.stringpool.SPObject)
*/
public int numericalCompare(SPObject o) {
if (!o.isNumber()) return compareTo(o);
return -((SPNumber) o).numericalCompareTo(l);
}