manuzhang commented on code in PR #14948: URL: https://github.com/apache/iceberg/pull/14948#discussion_r3245931645
########## spark/v4.1/spark/src/main/java/org/apache/iceberg/spark/source/MergingSortedRowDataReader.java: ########## @@ -0,0 +1,299 @@ +/* + * 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.Collections; +import java.util.Comparator; +import java.util.List; +import java.util.stream.Collectors; +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.relocated.com.google.common.base.Preconditions; +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.SortedMerge; +import org.apache.spark.sql.catalyst.InternalRow; +import org.apache.spark.sql.catalyst.expressions.GenericInternalRow; +import org.apache.spark.sql.connector.metric.CustomTaskMetric; +import org.apache.spark.sql.connector.read.PartitionReader; +import org.apache.spark.sql.types.DataType; +import org.apache.spark.sql.types.StructType; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * 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>This reader is used when {@code preserve-data-ordering} is enabled and the task group contains + * multiple files that all have the same sort order. + * + * <p>Sort key columns absent from the requested projection are temporarily added to the read schema + * so that {@link SortOrderComparators} can access them during the merge. The extra columns are + * stripped from each row before it is returned to Spark. + */ +class MergingSortedRowDataReader implements PartitionReader<InternalRow> { + private static final Logger LOG = LoggerFactory.getLogger(MergingSortedRowDataReader.class); + + private final CloseableGroup resources; + private final CloseableIterator<InternalRow> 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 int[] outputPositions; + private final DataType[] outputDataTypes; + private final Object[] outputValues; // reused per row to avoid per-row allocation + private InternalRow current; + + MergingSortedRowDataReader(SparkInputPartition partition) { + Table table = partition.table(); + ScanTaskGroup<FileScanTask> taskGroup = partition.taskGroup(); + Schema projection = partition.projection(); + SortOrder sortOrder = table.sortOrder(); + + Preconditions.checkState( + sortOrder.isSorted(), "Cannot create merging reader for unsorted table %s", table.name()); + Preconditions.checkState( + taskGroup.tasks().size() > 1, + "Merging reader requires multiple files, got %s", + taskGroup.tasks().size()); + + LOG.info( + "Creating merging reader for {} files with sort order {} in table {}", + taskGroup.tasks().size(), + 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.outputPositions = buildOutputPositions(projection, mergeReadSchema); + this.outputDataTypes = buildOutputDataTypes(projection, outputPositions); + this.outputValues = outputPositions != null ? new Object[outputPositions.length] : null; + + this.resources = new CloseableGroup(); + this.fileReaders = + taskGroup.tasks().stream() + .map( + task -> + new RowDataReader( + table, + partition.io(), + new BaseScanTaskGroup<>(Collections.singletonList(task)), + mergeReadSchema, + partition.isCaseSensitive(), + partition.cacheDeleteFilesOnExecutors())) + .collect(Collectors.toList()); Review Comment: nit: `toList` is more concise. -- This is an automated message from the Apache Git Service. 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