| // Copyright (C) 2022 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 com.google.common.collect.ImmutableList; |
| import com.google.common.collect.Ordering; |
| import com.google.gerrit.exceptions.StorageException; |
| import com.google.gerrit.index.IndexConfig; |
| import com.google.gerrit.index.PaginationType; |
| import com.google.gerrit.index.QueryOptions; |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| public class PaginatingSource<T> extends FilteredSource<T> { |
| |
| public PaginatingSource(DataSource<T> source, int start, IndexConfig indexConfig) { |
| super(source, start, 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 pageResultSize = 0; |
| for (T data : buffer(resultSet)) { |
| if (!isMatchable() || match(data)) { |
| r.add(data); |
| } |
| last = data; |
| pageResultSize++; |
| } |
| |
| if (last != null && source instanceof Paginated) { |
| // Restart source and continue if we have not filled the |
| // full limit the caller wants. |
| @SuppressWarnings("unchecked") |
| Paginated<T> p = (Paginated<T>) source; |
| QueryOptions opts = p.getOptions(); |
| final int limit = opts.limit(); |
| int pageSize = opts.pageSize(); |
| int pageSizeMultiplier = opts.pageSizeMultiplier(); |
| Object searchAfter = resultSet.searchAfter(); |
| int nextStart = pageResultSize; |
| while (pageResultSize == pageSize && r.size() <= limit) { // get 1 more than the limit |
| pageSize = getNextPageSize(pageSize, pageSizeMultiplier); |
| ResultSet<T> next = |
| indexConfig.paginationType().equals(PaginationType.SEARCH_AFTER) |
| ? p.restart(searchAfter, pageSize) |
| : p.restart(nextStart, pageSize); |
| pageResultSize = 0; |
| for (T data : buffer(next)) { |
| if (match(data)) { |
| r.add(data); |
| } |
| pageResultSize++; |
| if (r.size() > limit) { |
| break; |
| } |
| } |
| nextStart += pageResultSize; |
| 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() { |
| // TODO(hiesel): Implement |
| throw new UnsupportedOperationException("not implemented"); |
| } |
| |
| private int getNextPageSize(int pageSize, int pageSizeMultiplier) { |
| List<Integer> possiblePageSizes = new ArrayList<>(3); |
| try { |
| possiblePageSizes.add(Math.multiplyExact(pageSize, pageSizeMultiplier)); |
| } catch (ArithmeticException e) { |
| possiblePageSizes.add(Integer.MAX_VALUE); |
| } |
| if (indexConfig.maxPageSize() > 0) { |
| possiblePageSizes.add(indexConfig.maxPageSize()); |
| } |
| if (indexConfig.maxLimit() > 0) { |
| possiblePageSizes.add(indexConfig.maxLimit()); |
| } |
| return Ordering.natural().min(possiblePageSizes); |
| } |
| } |