Partition spooled pages while encoding data to segments #26013
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| /* | ||
| * 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 io.trino.operator; | ||
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| import com.google.common.collect.ImmutableList; | ||
| import io.trino.spi.Page; | ||
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| import java.util.ArrayDeque; | ||
| import java.util.ArrayList; | ||
| import java.util.Deque; | ||
| import java.util.List; | ||
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| import static com.google.common.base.Verify.verify; | ||
| import static io.trino.execution.buffer.PageSplitterUtil.splitPage; | ||
| import static java.lang.Math.clamp; | ||
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| public class SpoolingPagePartitioner | ||
| { | ||
| static final double LOWER_BOUND = 0.05; // 5% of the target size | ||
| static final double UPPER_BOUND = 0.1; // 10% of the target size | ||
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| private SpoolingPagePartitioner() {} | ||
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| public static List<List<Page>> partition(List<Page> pages, long targetSize) | ||
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There was a problem hiding this comment. We buffer multiple pages There was a problem hiding this comment. I get it - but why not partition page by page. Passing multiple pages makes interface more complex. Let me read deeper
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| { | ||
| Deque<Page> queue = new ArrayDeque<>(pages); | ||
| List<Page> currentPartition = new ArrayList<>(); | ||
| ImmutableList.Builder<List<Page>> partitions = ImmutableList.builder(); | ||
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| while (!queue.isEmpty()) { | ||
| Page currentPage = queue.removeFirst(); | ||
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| long remainingSize = targetSize - size(currentPartition); | ||
| verify(remainingSize >= 0, "Current partition size %s is larger than target size %s", size(currentPartition), targetSize); | ||
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| if (currentPage.getSizeInBytes() < remainingSize) { | ||
| currentPartition.add(currentPage); | ||
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| if (withinThreshold(size(currentPartition), targetSize)) { | ||
| partitions.add(ImmutableList.copyOf(currentPartition)); | ||
| currentPartition.clear(); | ||
| } | ||
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| continue; | ||
| } | ||
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| List<Page> currentPartitioned = new ArrayList<>(takeFromHead(currentPage, remainingSize, targetSize)); | ||
| currentPartition.add(currentPartitioned.removeFirst()); | ||
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| // Add the remaining split pages back to the queue in the original order | ||
| currentPartitioned.reversed().forEach(queue::addFirst); | ||
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| if (withinThreshold(size(currentPartition), targetSize)) { | ||
| partitions.add(ImmutableList.copyOf(currentPartition)); | ||
| currentPartition.clear(); | ||
| } | ||
| } | ||
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| // If there are any remaining pages in the current partition, add them as a final partition | ||
| if (!currentPartition.isEmpty()) { | ||
| partitions.add(ImmutableList.copyOf(currentPartition)); | ||
| } | ||
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| return partitions.build(); | ||
| } | ||
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| private static boolean withinThreshold(long page, long targetSize) | ||
| { | ||
| return page >= targetSize * (1 - LOWER_BOUND) && page <= targetSize * (1 + UPPER_BOUND); | ||
| } | ||
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| private static List<Page> takeFromHead(Page page, long targetHeadSize, long tailSplitSize) | ||
| { | ||
| verify(page.getSizeInBytes() >= targetHeadSize, "Page size %s must be greater than head size %s", page.getSizeInBytes(), targetHeadSize); | ||
| ImmutableList.Builder<Page> builder = ImmutableList.builder(); | ||
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| int positions = positionsWithBytes(page, targetHeadSize); | ||
| builder.add(page.getRegion(0, positions)); | ||
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| if (positions == page.getPositionCount()) { | ||
| return builder.build(); | ||
| } | ||
| builder.addAll(splitPage(page.getRegion(positions, page.getPositionCount() - positions), tailSplitSize)); | ||
| return builder.build(); | ||
| } | ||
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| private static long averageSizePerPosition(Page page) | ||
| { | ||
| return clamp(page.getSizeInBytes() / (long) page.getPositionCount(), 1, Integer.MAX_VALUE); | ||
| } | ||
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| private static int positionsWithBytes(Page page, long bytes) | ||
| { | ||
| long positions = bytes / averageSizePerPosition(page); | ||
| return clamp(positions, 1, page.getPositionCount()); | ||
| } | ||
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| private static long size(List<Page> pages) | ||
| { | ||
| return pages.stream().mapToLong(Page::getSizeInBytes).sum(); | ||
| } | ||
| } | ||
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those could be added in separate commit