com.hazelcast.query.impl.predicates.FlatteningVisitor Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2017, Hazelcast, Inc. All Rights Reserved.
*
* Licensed 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 com.hazelcast.query.impl.predicates;
import com.hazelcast.query.Predicate;
import com.hazelcast.query.impl.Indexes;
import java.util.ArrayList;
import java.util.List;
import static com.hazelcast.util.collection.ArrayUtils.createCopy;
/**
* Rewrites predicates:
*
* 1. AndPredicates flattening:
* (a = 1 and (b = 2 and c = 3)) into (a = 1 and b = 2 and c = 3)
*
* 2. OrPredicate flattening:
* (a = 1 or (b = 2 or c = 3)) into (a = 1 or b = 2 or c = 3)
*
* 3. NotElimination
* (not(P)) when P is {@link NegatablePredicate} is rewritten as P.negate()
*
*
*/
public class FlatteningVisitor extends AbstractVisitor {
@Override
public Predicate visit(AndPredicate andPredicate, Indexes indexes) {
Predicate[] originalPredicates = andPredicate.predicates;
List toBeAdded = null;
boolean modified = false;
Predicate[] target = originalPredicates;
for (int i = 0; i < target.length; i++) {
Predicate predicate = target[i];
if (predicate instanceof AndPredicate) {
Predicate[] subPredicates = ((AndPredicate) predicate).predicates;
if (!modified) {
modified = true;
target = createCopy(target);
}
toBeAdded = replaceFirstAndStoreOthers(target, subPredicates, i, toBeAdded);
}
}
Predicate[] newInners = createNewInners(target, toBeAdded);
if (newInners == originalPredicates) {
return andPredicate;
}
return new AndPredicate(newInners);
}
@Override
public Predicate visit(OrPredicate orPredicate, Indexes indexes) {
Predicate[] originalPredicates = orPredicate.predicates;
List toBeAdded = null;
boolean modified = false;
Predicate[] target = originalPredicates;
for (int i = 0; i < target.length; i++) {
Predicate predicate = target[i];
if (predicate instanceof OrPredicate) {
Predicate[] subPredicates = ((OrPredicate) predicate).predicates;
if (!modified) {
modified = true;
target = createCopy(target);
}
toBeAdded = replaceFirstAndStoreOthers(target, subPredicates, i, toBeAdded);
}
}
Predicate[] newInners = createNewInners(target, toBeAdded);
if (newInners == originalPredicates) {
return orPredicate;
}
return new OrPredicate(newInners);
}
private List replaceFirstAndStoreOthers(Predicate[] predicates, Predicate[] subPredicates,
int position, List store) {
if (subPredicates == null || subPredicates.length == 0) {
return store;
}
predicates[position] = subPredicates[0];
for (int j = 1; j < subPredicates.length; j++) {
if (store == null) {
store = new ArrayList();
}
store.add(subPredicates[j]);
}
return store;
}
private Predicate[] createNewInners(Predicate[] predicates, List toBeAdded) {
if (toBeAdded == null || toBeAdded.size() == 0) {
return predicates;
}
int newSize = predicates.length + toBeAdded.size();
Predicate[] newPredicates = new Predicate[newSize];
System.arraycopy(predicates, 0, newPredicates, 0, predicates.length);
for (int i = predicates.length; i < newSize; i++) {
newPredicates[i] = toBeAdded.get(i - predicates.length);
}
return newPredicates;
}
@Override
public Predicate visit(NotPredicate predicate, Indexes indexes) {
Predicate inner = predicate.predicate;
if (inner instanceof NegatablePredicate) {
return ((NegatablePredicate) inner).negate();
}
return predicate;
}
}