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// Copyright (C) 2023 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 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 java.util.ArrayList;
import java.util.List;
public class FilteredSource<T> implements DataSource<T> {
protected final DataSource<T> source;
protected final int start;
protected final int cardinality;
protected final IndexConfig indexConfig;
private static final int PARTITION_SIZE = 50;
public FilteredSource(DataSource<T> source, int start, IndexConfig indexConfig) {
checkArgument(start >= 0, "negative start: %s", start);
this.source = source;
this.start = start;
this.cardinality = source.getCardinality();
this.indexConfig = indexConfig;
}
@Override
public ResultSet<T> read() {
if (source == null) {
throw new StorageException("No DataSource defined.");
}
// 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<>();
for (T data : buffer(resultSet)) {
if (!isMatchable() || match(data)) {
r.add(data);
}
}
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() {
return source.readRaw();
}
protected Iterable<T> buffer(ResultSet<T> scanner) {
return FluentIterable.from(Iterables.partition(scanner, PARTITION_SIZE))
.transformAndConcat(this::transformBuffer);
}
protected List<T> transformBuffer(List<T> buffer) {
return buffer;
}
@Override
public int getCardinality() {
return cardinality;
}
protected boolean match(T object) {
return true;
}
protected boolean isMatchable() {
return true;
}
}
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