dramaticlly commented on code in PR #14948: URL: https://github.com/apache/iceberg/pull/14948#discussion_r3708238151
########## spark/v4.1/spark/src/main/java/org/apache/iceberg/spark/source/MergingSortedRowDataReader.java: ########## @@ -0,0 +1,331 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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 org.apache.iceberg.spark.source; + +import java.io.IOException; +import java.io.UncheckedIOException; +import java.util.Arrays; +import java.util.Comparator; +import java.util.List; +import java.util.Objects; +import org.apache.iceberg.Accessor; +import org.apache.iceberg.Accessors; +import org.apache.iceberg.BaseScanTaskGroup; +import org.apache.iceberg.FileScanTask; +import org.apache.iceberg.ScanTaskGroup; +import org.apache.iceberg.Schema; +import org.apache.iceberg.SortField; +import org.apache.iceberg.SortOrder; +import org.apache.iceberg.SortOrderComparators; +import org.apache.iceberg.StructLike; +import org.apache.iceberg.Table; +import org.apache.iceberg.io.CloseableGroup; +import org.apache.iceberg.io.CloseableIterable; +import org.apache.iceberg.io.CloseableIterator; +import org.apache.iceberg.io.FileIO; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList; +import org.apache.iceberg.relocated.com.google.common.collect.Lists; +import org.apache.iceberg.spark.SparkSchemaUtil; +import org.apache.iceberg.spark.source.metrics.TaskNumDeletes; +import org.apache.iceberg.spark.source.metrics.TaskNumSplits; +import org.apache.iceberg.types.TypeUtil; +import org.apache.iceberg.types.Types; +import org.apache.iceberg.util.Exceptions; +import org.apache.iceberg.util.SortedMerge; +import org.apache.spark.rdd.InputFileBlockHolder; +import org.apache.spark.sql.catalyst.InternalRow; +import org.apache.spark.sql.catalyst.ProjectingInternalRow; +import org.apache.spark.sql.connector.metric.CustomTaskMetric; +import org.apache.spark.sql.connector.read.PartitionReader; +import org.apache.spark.sql.types.StructType; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; +import scala.collection.JavaConverters; + +/** + * A {@link PartitionReader} that reads multiple sorted files and merges them into a single sorted + * stream using a k-way heap merge ({@link SortedMerge}). + * + * <p>Every file in the task group must be written with the table's current sort order. Sort keys on + * nested fields are not supported. + */ +class MergingSortedRowDataReader implements PartitionReader<InternalRow> { + private static final Logger LOG = LoggerFactory.getLogger(MergingSortedRowDataReader.class); + + private final CloseableGroup resources; + private final CloseableIterator<TaggedRow> mergedIterator; + private final List<RowDataReader> fileReaders; + // non-null only when sort key columns were added to the read schema beyond what Spark projected + private final ProjectingInternalRow projectingRow; + private InternalRow current; + private FileBlock currentBlock; + + MergingSortedRowDataReader(SparkInputPartition partition) { + this( + partition.table(), + partition.io(), + partition.taskGroup(), + partition.projection(), + partition.isCaseSensitive(), + partition.cacheDeleteFilesOnExecutors()); + } + + MergingSortedRowDataReader( + Table table, + FileIO io, + ScanTaskGroup<FileScanTask> taskGroup, + Schema projection, + boolean caseSensitive, + boolean cacheDeleteFilesOnExecutors) { + SortOrder sortOrder = table.sortOrder(); + int numFiles = taskGroup.tasks().size(); + + Preconditions.checkArgument( + sortOrder.isSorted(), "Cannot create merging reader for unsorted table %s", table.name()); + Preconditions.checkArgument( + numFiles > 1, "Merging reader requires multiple files, got %s", numFiles); + + int expectedOrderId = sortOrder.orderId(); + Preconditions.checkArgument( + taskGroup.tasks().stream() + .allMatch(task -> Objects.equals(task.file().sortOrderId(), expectedOrderId)), + "Not all files in task group have the expected sort order %s", + expectedOrderId); + + LOG.debug( + "Creating merging reader for {} files with sort order {} in table {}", + numFiles, + sortOrder.orderId(), + table.name()); + + // Augment the projected schema with any sort key columns Spark did not request so that + // SortOrderComparators can access every sort key field during the merge. + Schema mergeReadSchema = mergeReadSchema(projection, sortOrder, table); + this.projectingRow = buildProjectingRow(projection, mergeReadSchema); + + this.resources = new CloseableGroup(); + List<FileScanTask> tasks = Lists.newArrayList(taskGroup.tasks()); + this.fileReaders = + tasks.stream() + .map( + task -> + new RowDataReader( + table, + io, + new BaseScanTaskGroup<>(ImmutableList.of(task)), + mergeReadSchema, + caseSensitive, + cacheDeleteFilesOnExecutors)) + .toList(); + fileReaders.forEach(resources::addCloseable); + // Wrap each reader as a CloseableIterable and feed into SortedMerge. + List<CloseableIterable<TaggedRow>> fileIterables = Lists.newArrayListWithCapacity(tasks.size()); + for (int i = 0; i < tasks.size(); i++) { + fileIterables.add(readerToIterable(fileReaders.get(i), tasks.get(i))); + } + Comparator<InternalRow> rowComparator = buildComparator(mergeReadSchema, sortOrder); + SortedMerge<TaggedRow> sortedMerge = + new SortedMerge<>((a, b) -> rowComparator.compare(a.row(), b.row()), fileIterables); + resources.addCloseable(sortedMerge); + boolean threw = true; + try { + this.mergedIterator = sortedMerge.iterator(); + threw = false; + } finally { + if (threw) { + Exceptions.close(resources, true); + } + } + } + + /** + * Adapts a {@link RowDataReader} to a {@link CloseableIterable} for use with {@link SortedMerge}. + * + * <p>Rows are copied on the way into the heap. {@link SortedMerge} advances an iterator before + * returning the value it just polled, so an uncopied row would be overwritten by the next read + * from the same file since Spark's Parquet and ORC readers reuse {@link InternalRow} containers. + * At most one row per file is held at a time, so the copy is bounded by the number of files. + */ + private CloseableIterable<TaggedRow> readerToIterable(RowDataReader reader, FileScanTask task) { + FileBlock block = new FileBlock(task.file().location(), task.start(), task.length()); + return CloseableIterable.withNoopClose( + () -> + new CloseableIterator<>() { + private boolean advanced = false; + private boolean hasNext = false; + + @Override + public boolean hasNext() { + if (!advanced) { + try { + hasNext = reader.next(); + advanced = true; + } catch (IOException e) { + throw new UncheckedIOException("Failed to advance reader", e); + } + } + return hasNext; + } + + @Override + public TaggedRow next() { + if (!advanced) { + hasNext(); + } + advanced = false; + return new TaggedRow(reader.get().copy(), block); + } + + @Override + public void close() { + // Readers are owned by the enclosing CloseableGroup, not by the merge. SortedMerge + // drops iterators that are empty on the first hasNext() without closing them, so a + // file whose rows are all deleted would otherwise leak. Closing here too would + // double-close every reader the merge does drain. + } + }); + } + + @Override + public boolean next() throws IOException { + if (!mergedIterator.hasNext()) { + return false; + } + + TaggedRow tagged = mergedIterator.next(); + // all rows from one task share a FileBlock instance, so identity is enough to detect a switch + // and avoid re-allocating the block holder entry on every row + if (tagged.block() != currentBlock) { + FileBlock block = tagged.block(); + InputFileBlockHolder.set(block.filePath(), block.start(), block.length()); + this.currentBlock = block; + } + + InternalRow merged = tagged.row(); + if (projectingRow == null) { + this.current = merged; + } else { + projectingRow.project(merged); + this.current = projectingRow; + } + + return true; + } + + @Override + public InternalRow get() { + return current; + } + + @Override + public void close() throws IOException { + resources.close(); + } + + @Override + public CustomTaskMetric[] currentMetricsValues() { + long totalDeletes = + fileReaders.stream() + .flatMap(reader -> Arrays.stream(reader.currentMetricsValues())) + .filter(metric -> metric instanceof TaskNumDeletes) + .mapToLong(CustomTaskMetric::value) + .sum(); + return new CustomTaskMetric[] { + new TaskNumSplits(fileReaders.size()), new TaskNumDeletes(totalDeletes) + }; + } + + /** + * Builds a comparator for merging {@link InternalRow}s by the given sort order. Each side wraps + * its row in its own reusable {@link InternalRowWrapper} so the two arguments stay distinct. + */ + private static Comparator<InternalRow> buildComparator( + Schema mergeReadSchema, SortOrder sortOrder) { + StructType sparkSchema = SparkSchemaUtil.convert(mergeReadSchema); + Comparator<StructLike> keyComparator = + SortOrderComparators.forSchema(mergeReadSchema, sortOrder); Review Comment: Found a related issue in https://github.com/apache/iceberg/issues/14216, I think at minimal we shall exclude the sortKey with UUID type. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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