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// Copyright (C) 2016 The Android Open Source Project
//
// 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.google.gerrit.index.query;
import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.collect.ImmutableList.toImmutableList;
import com.google.common.collect.FluentIterable;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.gerrit.exceptions.StorageException;
import com.google.gerrit.index.IndexConfig;
import com.google.gerrit.index.PaginationType;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Comparator;
import java.util.List;
public class AndSource<T> extends AndPredicate<T>
implements DataSource<T>, Comparator<Predicate<T>> {
protected final DataSource<T> source;
private final IsVisibleToPredicate<T> isVisibleToPredicate;
private final int start;
private final int cardinality;
private final IndexConfig indexConfig;
public AndSource(Collection<? extends Predicate<T>> that, IndexConfig indexConfig) {
this(that, null, 0, indexConfig);
}
public AndSource(
Predicate<T> that, IsVisibleToPredicate<T> isVisibleToPredicate, IndexConfig indexConfig) {
this(that, isVisibleToPredicate, 0, indexConfig);
}
public AndSource(
Predicate<T> that,
IsVisibleToPredicate<T> isVisibleToPredicate,
int start,
IndexConfig indexConfig) {
this(ImmutableList.of(that), isVisibleToPredicate, start, indexConfig);
}
public AndSource(
Collection<? extends Predicate<T>> that,
IsVisibleToPredicate<T> isVisibleToPredicate,
int start,
IndexConfig indexConfig) {
super(that);
checkArgument(start >= 0, "negative start: %s", start);
this.isVisibleToPredicate = isVisibleToPredicate;
this.start = start;
int c = Integer.MAX_VALUE;
DataSource<T> s = null;
int minCost = Integer.MAX_VALUE;
for (Predicate<T> p : sort(getChildren())) {
if (p instanceof DataSource) {
c = Math.min(c, ((DataSource<?>) p).getCardinality());
int cost = p.estimateCost();
if (cost < minCost) {
s = toDataSource(p);
minCost = cost;
}
}
}
this.source = s;
this.cardinality = c;
this.indexConfig = indexConfig;
}
@Override
public ResultSet<T> read() {
if (source == null) {
throw new StorageException("No DataSource: " + this);
}
// ResultSets are lazy. Calling #read here first and then dealing with ResultSets only when
// requested allows the index to run asynchronous queries.
ResultSet<T> resultSet = source.read();
return new LazyResultSet<>(
() -> {
List<T> r = new ArrayList<>();
T last = null;
int nextStart = 0;
boolean skipped = false;
for (T data : buffer(resultSet)) {
if (!isMatchable() || match(data)) {
r.add(data);
} else {
skipped = true;
}
last = data;
nextStart++;
}
if (skipped && last != null && source instanceof Paginated) {
// If our source is a paginated source and we skipped at
// least one of its results, we may not have filled the full
// limit the caller wants. Restart the source and continue.
//
@SuppressWarnings("unchecked")
Paginated<T> p = (Paginated<T>) source;
Object searchAfter = resultSet.searchAfter();
while (skipped && r.size() < p.getOptions().limit() + start) {
skipped = false;
ResultSet<T> next =
indexConfig.paginationType().equals(PaginationType.SEARCH_AFTER)
? p.restart(searchAfter)
: p.restart(nextStart);
for (T data : buffer(next)) {
if (match(data)) {
r.add(data);
} else {
skipped = true;
}
nextStart++;
}
searchAfter = next.searchAfter();
}
}
if (start >= r.size()) {
return ImmutableList.of();
} else if (start > 0) {
return ImmutableList.copyOf(r.subList(start, r.size()));
}
return ImmutableList.copyOf(r);
});
}
@Override
public ResultSet<FieldBundle> readRaw() {
// TOOD(hiesel): Implement
throw new UnsupportedOperationException("not implemented");
}
@Override
public boolean isMatchable() {
return isVisibleToPredicate != null || super.isMatchable();
}
@Override
public boolean match(T object) {
if (isVisibleToPredicate != null && !isVisibleToPredicate.match(object)) {
return false;
}
if (super.isMatchable() && !super.match(object)) {
return false;
}
return true;
}
private Iterable<T> buffer(ResultSet<T> scanner) {
return FluentIterable.from(Iterables.partition(scanner, 50))
.transformAndConcat(this::transformBuffer);
}
protected List<T> transformBuffer(List<T> buffer) {
return buffer;
}
@Override
public int getCardinality() {
return cardinality;
}
private ImmutableList<Predicate<T>> sort(Collection<? extends Predicate<T>> that) {
return that.stream().sorted(this).collect(toImmutableList());
}
@Override
public int compare(Predicate<T> a, Predicate<T> b) {
int ai = a instanceof DataSource ? 0 : 1;
int bi = b instanceof DataSource ? 0 : 1;
int cmp = ai - bi;
if (cmp == 0) {
cmp = a.estimateCost() - b.estimateCost();
}
if (cmp == 0 && a instanceof DataSource && b instanceof DataSource) {
DataSource<?> as = (DataSource<?>) a;
DataSource<?> bs = (DataSource<?>) b;
cmp = as.getCardinality() - bs.getCardinality();
}
return cmp;
}
@SuppressWarnings("unchecked")
private DataSource<T> toDataSource(Predicate<T> pred) {
return (DataSource<T>) pred;
}
}
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