@Override public Stream<IQ> splitUnion(IQ query) { DistinctVariableOnlyDataAtom projectionAtom = query.getProjectionAtom(); VariableGenerator variableGenerator = query.getVariableGenerator(); IQTree tree = query.getTree(); return findFirstSplittableUnion(query) .map(unionTree -> unionTree.getChildren().stream() .map(c -> tree.replaceSubTree(unionTree, c)) .map(t -> t.liftBinding(variableGenerator)) .map(t -> iqFactory.createIQ(projectionAtom, t)) .map(IQ::liftBinding)) .orElseGet(() -> Stream.of(query)); }
/** * */ private IQ liftUnionsInTree(IQ query) { VariableGenerator variableGenerator = query.getVariableGenerator(); // Non-final IQTree previousTree; IQTree newTree = query.getTree(); int i=0; do { previousTree = newTree; newTree = liftTree(previousTree, variableGenerator) .liftBinding(variableGenerator); } while (!newTree.equals(previousTree) && (++i < ITERATION_BOUND)); if (i >= ITERATION_BOUND) throw new MinorOntopInternalBugException(getClass().getName() + " did not converge after " + ITERATION_BOUND + " iterations"); return newTree.equals(query.getTree()) ? query : iqFactory.createIQ(query.getProjectionAtom(), newTree); }
/** * TODO: why a fix point? */ @Override public IQ optimize(IQ query) { TreeTransformer treeTransformer = new TreeTransformer(query.getVariableGenerator()); IQ prev; do { prev = query; query = iqFactory.createIQ( query.getProjectionAtom(), query.getTree().acceptTransformer(treeTransformer) ); } while (!prev.equals(query)); return query; } }
private IQ normalizeIQ(IntermediateQuery intermediateQuery) { // Trick for pushing down expressions under unions: // - there the context may be concrete enough for evaluating certain expressions // - useful for dealing with SPARQL EBVs for instance IntermediateQuery pushedDownQuery = pushDownExpressionOptimizer.optimize(intermediateQuery); log.debug("New query after pushing down the boolean expressions (temporary): \n" + pushedDownQuery); IQ flattenIQ = unionFlattener.optimize(iqConverter.convert(pushedDownQuery)); log.debug("New query after flattening the union: \n" + flattenIQ); IQTree treeAfterPullOut = optimizerFactory.createEETransformer(flattenIQ.getVariableGenerator()).transform(flattenIQ.getTree()); log.debug("Query tree after pulling out equalities: \n" + treeAfterPullOut); // Pulling up is needed when filtering conditions appear above a data atom on the left // (causes problems to the IQ2DatalogConverter) try { IntermediateQuery queryAfterPullUp = pullUpExpressionOptimizer.optimize(iqConverter.convert( iqFactory.createIQ(flattenIQ.getProjectionAtom(), treeAfterPullOut), intermediateQuery.getDBMetadata(), intermediateQuery.getExecutorRegistry())); log.debug("New query after pulling up the boolean expressions: \n" + queryAfterPullUp); return iqConverter.convert(queryAfterPullUp); } catch (EmptyQueryException e) { // Not expected throw new MinorOntopInternalBugException(e.getMessage()); } }
Variable originalObject = rdfAtomPredicate.getObject(originalProjectedVariables); VariableGenerator originalVariableGenerator = originalDefinition.getVariableGenerator();