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

Example 1 with GroupElem

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

the class TupleExprBuilder method visit.

@Override
public TupleExpr visit(ASTSelect node, Object data) throws VisitorException {
    TupleExpr result = (TupleExpr) data;
    final Order orderClause = result instanceof Order ? (Order) result : null;
    Extension extension = new Extension();
    ProjectionElemList projElemList = new ProjectionElemList();
    GroupFinder groupFinder = new GroupFinder();
    result.visit(groupFinder);
    Group group = groupFinder.getGroup();
    boolean existingGroup = group != null;
    List<String> aliasesInProjection = new ArrayList<String>();
    for (ASTProjectionElem projElemNode : node.getProjectionElemList()) {
        Node child = projElemNode.jjtGetChild(0);
        String alias = projElemNode.getAlias();
        if (alias != null) {
            // aliased projection element
            if (aliasesInProjection.contains(alias)) {
                throw new VisitorException("duplicate use of alias '" + alias + "' in projection.");
            }
            // check if alias is not previously used.
            if (result.getBindingNames().contains(alias)) {
                throw new VisitorException("projection alias '" + alias + "' was previously used");
            }
            aliasesInProjection.add(alias);
            ValueExpr valueExpr = (ValueExpr) child.jjtAccept(this, null);
            String targetName = alias;
            String sourceName = alias;
            if (child instanceof ASTVar) {
                sourceName = ((ASTVar) child).getName();
            }
            ProjectionElem elem = new ProjectionElem(sourceName, targetName);
            projElemList.addElement(elem);
            AggregateCollector collector = new AggregateCollector();
            valueExpr.visit(collector);
            if (collector.getOperators().size() > 0) {
                elem.setAggregateOperatorInExpression(true);
                for (AggregateOperator operator : collector.getOperators()) {
                    // Apply implicit grouping if necessary
                    if (group == null) {
                        group = new Group(result);
                    }
                    if (operator.equals(valueExpr)) {
                        group.addGroupElement(new GroupElem(alias, operator));
                        extension.setArg(group);
                    } else {
                        ValueExpr expr = (ValueExpr) operator.getParentNode();
                        Extension anonymousExtension = new Extension();
                        Var anonVar = createAnonVar();
                        expr.replaceChildNode(operator, anonVar);
                        anonymousExtension.addElement(new ExtensionElem(operator, anonVar.getName()));
                        anonymousExtension.setArg(result);
                        result = anonymousExtension;
                        group.addGroupElement(new GroupElem(anonVar.getName(), operator));
                    }
                    if (!existingGroup) {
                        result = group;
                    }
                }
            }
            // add extension element reference to the projection element and
            // to
            // the extension
            ExtensionElem extElem = new ExtensionElem(valueExpr, alias);
            extension.addElement(extElem);
            elem.setSourceExpression(extElem);
        } else if (child instanceof ASTVar) {
            Var projVar = (Var) child.jjtAccept(this, null);
            ProjectionElem elem = new ProjectionElem(projVar.getName());
            projElemList.addElement(elem);
            VarCollector whereClauseVarCollector = new VarCollector();
            result.visit(whereClauseVarCollector);
            if (!whereClauseVarCollector.collectedVars.contains(projVar)) {
                ExtensionElem extElem = new ExtensionElem(projVar, projVar.getName());
                extension.addElement(extElem);
                elem.setSourceExpression(extElem);
            }
        } else {
            throw new IllegalStateException("required alias for non-Var projection elements not found");
        }
    }
    if (!extension.getElements().isEmpty()) {
        if (orderClause != null) {
            // Extensions produced by SELECT expressions should be nested
            // inside
            // the ORDER BY clause, to make sure
            // sorting can work on the newly introduced variable. See
            // SES-892
            // and SES-1809.
            TupleExpr arg = orderClause.getArg();
            extension.setArg(arg);
            orderClause.setArg(extension);
            result = orderClause;
        } else {
            extension.setArg(result);
            result = extension;
        }
    }
    result = new Projection(result, projElemList);
    if (group != null) {
        for (ProjectionElem elem : projElemList.getElements()) {
            if (!elem.hasAggregateOperatorInExpression()) {
                Set<String> groupNames = group.getBindingNames();
                ExtensionElem extElem = elem.getSourceExpression();
                if (extElem != null) {
                    ValueExpr expr = extElem.getExpr();
                    VarCollector collector = new VarCollector();
                    expr.visit(collector);
                    for (Var var : collector.getCollectedVars()) {
                        if (!groupNames.contains(var.getName())) {
                            throw new VisitorException("variable '" + var.getName() + "' in projection not present in GROUP BY.");
                        }
                    }
                } else {
                    if (!groupNames.contains(elem.getTargetName())) {
                        throw new VisitorException("variable '" + elem.getTargetName() + "' in projection not present in GROUP BY.");
                    } else if (!groupNames.contains(elem.getSourceName())) {
                        throw new VisitorException("variable '" + elem.getSourceName() + "' in projection not present in GROUP BY.");
                    }
                }
            }
        }
    }
    if (node.isSubSelect()) {
        // set context var at the level of the projection. This allows us
        // to distinguish named graphs selected in the
        // outer query from named graphs selected as part of the sub-select.
        ((Projection) result).setProjectionContext(graphPattern.getContextVar());
    }
    if (node.isDistinct()) {
        result = new Distinct(result);
    } else if (node.isReduced()) {
        result = new Reduced(result);
    }
    return result;
}

Example 2 with GroupElem

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

the class TupleExprBuilder method processOrderClause.

private TupleExpr processOrderClause(ASTOrderClause orderNode, TupleExpr tupleExpr, Group group) throws VisitorException {
    if (orderNode != null) {
        @SuppressWarnings("unchecked") List<OrderElem> orderElements = (List<OrderElem>) orderNode.jjtAccept(this, null);
        for (OrderElem orderElem : orderElements) {
            // retrieve any aggregate operators from the order element.
            AggregateCollector collector = new AggregateCollector();
            collector.meet(orderElem);
            Extension extension = new Extension();
            for (AggregateOperator operator : collector.getOperators()) {
                Var var = createAnonVar();
                // replace occurrence of the operator in the order condition
                // with the variable.
                AggregateOperatorReplacer replacer = new AggregateOperatorReplacer(operator, var);
                replacer.meet(orderElem);
                // create an extension linking the operator to the variable
                // name.
                String alias = var.getName();
                ExtensionElem pe = new ExtensionElem(operator, alias);
                extension.addElement(pe);
                // add the aggregate operator to the group.
                GroupElem ge = new GroupElem(alias, operator);
                group.addGroupElement(ge);
            }
            if (!extension.getElements().isEmpty()) {
                extension.setArg(tupleExpr);
                tupleExpr = extension;
            }
        }
        tupleExpr = new Order(tupleExpr, orderElements);
    }
    return tupleExpr;
}

Example 3 with GroupElem

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

the class TupleExprBuilder method processHavingClause.

private TupleExpr processHavingClause(ASTHavingClause havingNode, TupleExpr tupleExpr, Group group) throws VisitorException {
    if (havingNode != null) {
        // create an implicit group
        if (group == null) {
            group = new Group(tupleExpr);
        }
        ValueExpr expr = (ValueExpr) havingNode.jjtGetChild(0).jjtAccept(this, tupleExpr);
        // retrieve any aggregate operators from the expression.
        AggregateCollector collector = new AggregateCollector();
        collector.meetOther(expr);
        // replace operator occurrences with an anonymous var, and alias it
        // to the group
        Extension extension = new Extension();
        for (AggregateOperator operator : collector.getOperators()) {
            Var var = createAnonVar();
            // replace occurrence of the operator in the filter expression
            // with the variable.
            AggregateOperatorReplacer replacer = new AggregateOperatorReplacer(operator, var);
            replacer.meetOther(expr);
            String alias = var.getName();
            // create an extension linking the operator to the variable
            // name.
            ExtensionElem pe = new ExtensionElem(operator, alias);
            extension.addElement(pe);
            // add the aggregate operator to the group.
            GroupElem ge = new GroupElem(alias, operator);
            // FIXME quite often the aggregate in the HAVING clause will be
            // a duplicate of an aggregate in the projection. We could
            // perhaps
            // optimize for that, to avoid having to evaluate twice.
            group.addGroupElement(ge);
        }
        extension.setArg(group);
        tupleExpr = new Filter(extension, expr);
    }
    return tupleExpr;
}