| // 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; |
| } |
| } |