Examples with EmptySet org.eclipse.rdf4j.query.algebra.EmptySet used on opensource projects

Example 1 with EmptySet

use of org.eclipse.rdf4j.query.algebra.EmptySet in project rdf4j by eclipse.

the class TupleExprBuilder method visit.

@Override
public TupleExpr visit(ASTConstruct node, Object data) throws VisitorException {
    TupleExpr result = (TupleExpr) data;
    // Collect construct triples
    graphPattern = new GraphPattern();
    super.visit(node, null);
    TupleExpr constructExpr = graphPattern.buildTupleExpr();
    // Retrieve all StatementPatterns from the construct expression
    List<StatementPattern> statementPatterns = StatementPatternCollector.process(constructExpr);
    if (constructExpr instanceof Filter) {
        // sameTerm filters in construct (this can happen when there's a
        // cyclic
        // path defined, see SES-1685 and SES-2104)
        // we remove the sameTerm filters by simply replacing all mapped
        // variable occurrences
        Set<SameTerm> sameTermConstraints = getSameTermConstraints((Filter) constructExpr);
        statementPatterns = replaceSameTermVars(statementPatterns, sameTermConstraints);
    }
    Set<Var> constructVars = getConstructVars(statementPatterns);
    VarCollector whereClauseVarCollector = new VarCollector();
    result.visit(whereClauseVarCollector);
    // Create BNodeGenerators for all anonymous variables
    // NB: preserve order for a deterministic output
    Map<Var, ExtensionElem> extElemMap = new LinkedHashMap<Var, ExtensionElem>();
    for (Var var : constructVars) {
        if (var.isAnonymous() && !extElemMap.containsKey(var)) {
            ValueExpr valueExpr;
            if (var.hasValue()) {
                valueExpr = new ValueConstant(var.getValue());
            } else {
                valueExpr = new BNodeGenerator();
            }
            extElemMap.put(var, new ExtensionElem(valueExpr, var.getName()));
        } else if (!whereClauseVarCollector.collectedVars.contains(var)) {
            // non-anon var in construct clause not present in where clause
            if (!extElemMap.containsKey(var)) {
                // assign non-anonymous vars not present in where clause as
                // extension elements. This is necessary to make external
                // binding
                // assingnment possible (see SES-996)
                extElemMap.put(var, new ExtensionElem(var, var.getName()));
            }
        }
    }
    if (!extElemMap.isEmpty()) {
        result = new Extension(result, extElemMap.values());
    }
    // Create a Projection for each StatementPattern in the constructor
    List<ProjectionElemList> projList = new ArrayList<ProjectionElemList>();
    for (StatementPattern sp : statementPatterns) {
        ProjectionElemList projElemList = new ProjectionElemList();
        projElemList.addElement(new ProjectionElem(sp.getSubjectVar().getName(), "subject"));
        projElemList.addElement(new ProjectionElem(sp.getPredicateVar().getName(), "predicate"));
        projElemList.addElement(new ProjectionElem(sp.getObjectVar().getName(), "object"));
        if (sp.getContextVar() != null) {
            projElemList.addElement(new ProjectionElem(sp.getContextVar().getName(), "context"));
        }
        projList.add(projElemList);
    }
    if (projList.size() == 1) {
        result = new Projection(result, projList.get(0));
    } else if (projList.size() > 1) {
        result = new MultiProjection(result, projList);
    } else {
        // Empty constructor
        result = new EmptySet();
    }
    return new Reduced(result);
}

Example 2 with EmptySet

use of org.eclipse.rdf4j.query.algebra.EmptySet in project rdf4j by eclipse.

the class ConstructorBuilder method buildConstructor.

private TupleExpr buildConstructor(TupleExpr bodyExpr, TupleExpr constructExpr, boolean explicitConstructor, boolean distinct, boolean reduced) {
    TupleExpr result = bodyExpr;
    // Retrieve all StatementPattern's from the construct expression
    List<StatementPattern> statementPatterns = StatementPatternCollector.process(constructExpr);
    Set<Var> constructVars = getConstructVars(statementPatterns);
    // Finally, the spo-bindings are again filtered for duplicates.
    if (distinct || reduced) {
        // Create projection that removes all bindings that are not used in the
        // constructor
        ProjectionElemList projElemList = new ProjectionElemList();
        for (Var var : constructVars) {
            // the distinct
            if (!var.isAnonymous() && !var.hasValue()) {
                projElemList.addElement(new ProjectionElem(var.getName()));
            }
        }
        result = new Projection(result, projElemList);
        // Filter the duplicates from these projected bindings
        if (distinct) {
            result = new Distinct(result);
        } else {
            result = new Reduced(result);
        }
    }
    // Create BNodeGenerator's for all anonymous variables
    Map<Var, ExtensionElem> extElemMap = new HashMap<Var, ExtensionElem>();
    for (Var var : constructVars) {
        if (var.isAnonymous() && !extElemMap.containsKey(var)) {
            ValueExpr valueExpr = null;
            if (var.hasValue()) {
                valueExpr = new ValueConstant(var.getValue());
            } else if (explicitConstructor) {
                // only generate bnodes in case of an explicit constructor
                valueExpr = new BNodeGenerator();
            }
            if (valueExpr != null) {
                extElemMap.put(var, new ExtensionElem(valueExpr, var.getName()));
            }
        }
    }
    if (!extElemMap.isEmpty()) {
        result = new Extension(result, extElemMap.values());
    }
    // Create a Projection for each StatementPattern in the constructor
    List<ProjectionElemList> projections = new ArrayList<ProjectionElemList>();
    for (StatementPattern sp : statementPatterns) {
        ProjectionElemList projElemList = new ProjectionElemList();
        projElemList.addElement(new ProjectionElem(sp.getSubjectVar().getName(), "subject"));
        projElemList.addElement(new ProjectionElem(sp.getPredicateVar().getName(), "predicate"));
        projElemList.addElement(new ProjectionElem(sp.getObjectVar().getName(), "object"));
        projections.add(projElemList);
    }
    if (projections.size() == 1) {
        result = new Projection(result, projections.get(0));
    // Note: no need to apply the second duplicate elimination step if
    // there's just one projection
    } else if (projections.size() > 1) {
        result = new MultiProjection(result, projections);
        if (distinct) {
            // Add another distinct to filter duplicate statements
            result = new Distinct(result);
        } else if (reduced) {
            result = new Reduced(result);
        }
    } else {
        // Empty constructor
        result = new EmptySet();
    }
    return result;
}

Example 3 with EmptySet

use of org.eclipse.rdf4j.query.algebra.EmptySet in project rdf4j by eclipse.

the class BasicGroup method expr.

private TupleExpr expr(boolean filterExpr) {
    TupleExpr aExpr = null;
    if (mExpressions.isEmpty() && mFilters.isEmpty()) {
        if (mChildren.isEmpty()) {
            return null;
        }
    } else if (mExpressions.isEmpty() && !mFilters.isEmpty()) {
        if (mChildren.isEmpty()) {
            aExpr = new Filter(new EmptySet(), filtersAsAnd());
        }
    } else {
        aExpr = asJoin(mExpressions);
        if (filterExpr) {
            aExpr = filteredTuple(aExpr);
        }
    }
    if (!mChildren.isEmpty()) {
        for (Group aGroup : mChildren) {
            if (aExpr == null) {
                if (mExpressions.isEmpty() && !mFilters.isEmpty()) {
                    aExpr = new Filter(aGroup.expr(), filtersAsAnd());
                } else {
                    aExpr = aGroup.expr();
                }
            } else {
                BinaryTupleOperator aJoin = aGroup.isOptional() ? new LeftJoin() : new Join();
                aJoin.setLeftArg(aExpr);
                if (aGroup.isOptional() && aJoin instanceof LeftJoin && aGroup instanceof BasicGroup && !((BasicGroup) aGroup).mFilters.isEmpty()) {
                    BasicGroup aBasicGroup = (BasicGroup) aGroup;
                    aJoin.setRightArg(aBasicGroup.expr(false));
                    ((LeftJoin) aJoin).setCondition(aBasicGroup.filtersAsAnd());
                } else {
                    aJoin.setRightArg(aGroup.expr());
                }
                aExpr = aJoin;
            }
        }
    }
    return aExpr;
}

Example 4 with EmptySet

use of org.eclipse.rdf4j.query.algebra.EmptySet in project rdf4j by eclipse.

the class ConstructorBuilder method buildConstructor.

private TupleExpr buildConstructor(TupleExpr bodyExpr, TupleExpr constructExpr, boolean explicitConstructor, boolean distinct, boolean reduced) {
    TupleExpr result = bodyExpr;
    // Retrieve all StatementPattern's from the construct expression
    List<StatementPattern> statementPatterns = StatementPatternCollector.process(constructExpr);
    Set<Var> constructVars = getConstructVars(statementPatterns);
    // Finally, the spo-bindings are again filtered for duplicates.
    if (distinct || reduced) {
        // Create projection that removes all bindings that are not used in the
        // constructor
        ProjectionElemList projElemList = new ProjectionElemList();
        for (Var var : constructVars) {
            // the distinct
            if (!var.isAnonymous() && !var.hasValue()) {
                projElemList.addElement(new ProjectionElem(var.getName()));
            }
        }
        result = new Projection(result, projElemList);
        // Filter the duplicates from these projected bindings
        if (distinct) {
            result = new Distinct(result);
        } else {
            result = new Reduced(result);
        }
    }
    // Create BNodeGenerator's for all anonymous variables
    Map<Var, ExtensionElem> extElemMap = new HashMap<Var, ExtensionElem>();
    for (Var var : constructVars) {
        if (var.isAnonymous() && !extElemMap.containsKey(var)) {
            ValueExpr valueExpr = null;
            if (var.hasValue()) {
                valueExpr = new ValueConstant(var.getValue());
            } else if (explicitConstructor) {
                // only generate bnodes in case of an explicit constructor
                valueExpr = new BNodeGenerator();
            }
            if (valueExpr != null) {
                extElemMap.put(var, new ExtensionElem(valueExpr, var.getName()));
            }
        }
    }
    if (!extElemMap.isEmpty()) {
        result = new Extension(result, extElemMap.values());
    }
    // Create a Projection for each StatementPattern in the constructor
    List<ProjectionElemList> projections = new ArrayList<ProjectionElemList>();
    for (StatementPattern sp : statementPatterns) {
        ProjectionElemList projElemList = new ProjectionElemList();
        projElemList.addElement(new ProjectionElem(sp.getSubjectVar().getName(), "subject"));
        projElemList.addElement(new ProjectionElem(sp.getPredicateVar().getName(), "predicate"));
        projElemList.addElement(new ProjectionElem(sp.getObjectVar().getName(), "object"));
        projections.add(projElemList);
    }
    if (projections.size() == 1) {
        result = new Projection(result, projections.get(0));
    // Note: no need to apply the second duplicate elimination step if
    // there's just one projection
    } else if (projections.size() > 1) {
        result = new MultiProjection(result, projections);
        if (distinct) {
            // Add another distinct to filter duplicate statements
            result = new Distinct(result);
        } else if (reduced) {
            result = new Reduced(result);
        }
    } else {
        // Empty constructor
        result = new EmptySet();
    }
    return result;
}

Example 5 with EmptySet

use of org.eclipse.rdf4j.query.algebra.EmptySet in project rdf4j by eclipse.

the class AbstractQueryBuilder method groupAsJoin.

private TupleExpr groupAsJoin(List<Group> theList) {
    BinaryTupleOperator aJoin = new Join();
    Filter aFilter = null;
    for (Group aGroup : theList) {
        TupleExpr aExpr = aGroup.expr();
        if (aExpr == null) {
            continue;
        }
        if (aExpr instanceof Filter && (((Filter) aExpr).getArg() == null || ((Filter) aExpr).getArg() instanceof EmptySet)) {
            if (aFilter == null) {
                aFilter = (Filter) aExpr;
            } else {
                // if we already have a filter w/ an empty arg, let's And the
                // conditions together.
                aFilter.setCondition(new And(aFilter.getCondition(), ((Filter) aExpr).getCondition()));
            }
            continue;
        }
        if (aFilter != null) {
            aFilter.setArg(aExpr);
            aExpr = aFilter;
            aFilter = null;
        }
        if (aGroup.isOptional()) {
            LeftJoin lj = new LeftJoin();
            TupleExpr aLeft = joinOrExpr(aJoin);
            if (aLeft != null) {
                lj.setLeftArg(aLeft);
                lj.setRightArg(aExpr);
                aJoin = lj;
                continue;
            }
        }
        if (aJoin.getLeftArg() == null) {
            aJoin.setLeftArg(aExpr);
        } else if (aJoin.getRightArg() == null) {
            aJoin.setRightArg(aExpr);
        } else {
            Join aNewJoin = new Join();
            aNewJoin.setLeftArg(aJoin);
            aNewJoin.setRightArg(aExpr);
            aJoin = aNewJoin;
        }
    }
    TupleExpr aExpr = joinOrExpr(aJoin);
    if (aFilter != null) {
        aFilter.setArg(aExpr);
        aExpr = aFilter;
    }
    return aExpr;
}