/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.jena.sparql.expr.aggregate;
import org.apache.jena.graph.Node ;
import org.apache.jena.sparql.expr.ExprList ;
import org.apache.jena.sparql.graph.NodeTransform;
import org.apache.jena.sparql.serializer.SerializationContext ;
/** An Aggregator is the processor for the whole result stream.
* BindingKeys identify which section of a group we're in. */
public interface Aggregator
{
//-- Aggregator - per query (strictly, one per SELECT level), unique even if mentioned several times.
//-- Accumulator - per group per key section processors (from AggregatorBase)
/** Create an accumulator for this aggregator */
public Accumulator createAccumulator() ;
/** Value if there are no groups : return null for no result */
public Node getValueEmpty() ;
public String toPrefixString() ;
// Key to identify an aggregator as syntax for duplicate use in a query.
public String key() ;
/** Get the SPARQL name (COUNT, AVG etc) */
public String getName() ;
public ExprList getExprList() ;
public Aggregator copy(ExprList exprs) ;
public Aggregator copyTransform(NodeTransform transform) ;
@Override
public int hashCode() ;
@Override
public boolean equals(Object other) ;
/** Consider this 'protected' */
public boolean equals(Aggregator other, boolean bySyntax) ;
/** Format as an (extended) SPARQL expression */
public String asSparqlExpr(SerializationContext sCxt) ;
}