anuragmantri commented on code in PR #14948: URL: https://github.com/apache/iceberg/pull/14948#discussion_r3598787575
########## spark/v4.1/spark/src/main/java/org/apache/iceberg/spark/source/MergingSortedRowDataReader.java: ########## @@ -0,0 +1,284 @@ +/* + * 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 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.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.SortedMerge; +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>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 ProjectingInternalRow projectingRow; + private InternalRow current; + + MergingSortedRowDataReader(SparkInputPartition partition) { + Table table = partition.table(); + ScanTaskGroup<FileScanTask> taskGroup = partition.taskGroup(); + Schema projection = partition.projection(); + SortOrder sortOrder = table.sortOrder(); + + int numFiles = taskGroup.tasks().size(); + + Preconditions.checkState( + sortOrder.isSorted(), "Cannot create merging reader for unsorted table %s", table.name()); + Preconditions.checkState( + numFiles > 1, "Merging reader requires multiple files, got %s", numFiles); + + LOG.info( + "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(); + this.fileReaders = + taskGroup.tasks().stream() + .map( + task -> + new RowDataReader( + table, + partition.io(), + new BaseScanTaskGroup<>(ImmutableList.of(task)), + mergeReadSchema, + partition.isCaseSensitive(), + partition.cacheDeleteFilesOnExecutors())) + .toList(); + fileReaders.forEach(resources::addCloseable); + // Wrap each reader as a CloseableIterable and feed into SortedMerge. + List<CloseableIterable<InternalRow>> fileIterables = + fileReaders.stream().map(this::readerToIterable).toList(); + SortedMerge<InternalRow> sortedMerge = + new SortedMerge<>(buildComparator(mergeReadSchema, sortOrder), fileIterables); + resources.addCloseable(sortedMerge); + this.mergedIterator = sortedMerge.iterator(); + } + + /** + * Adapts a {@link RowDataReader} to a {@link CloseableIterable} for use with {@link SortedMerge}. + * Each row is copied before it enters the priority queue because Spark's Parquet/ORC readers + * reuse {@link InternalRow} instances for performance. + */ + private CloseableIterable<InternalRow> readerToIterable(RowDataReader reader) { + 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 InternalRow next() { + if (!advanced) { + hasNext(); + } + advanced = false; + return reader.get().copy(); + } + + @Override + public void close() { + // No-op. The RowDataReaders are owned by the enclosing CloseableGroup + // (resources) and closed exactly once from close(). SortedMerge cannot be the + // sole owner because it filters out empty iterators (for example a file whose + // rows are all removed by deletes), so those readers would never be closed + // through the merge. Closing here as well would double-close the readers that + // SortedMerge does drain. + } + }); + } + + @Override + public boolean next() throws IOException { + if (!mergedIterator.hasNext()) { + return false; + } + + InternalRow merged = mergedIterator.next(); + 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. Uses {@link + * SortOrderComparators} which handles all transform types (identity, bucket, truncate), ASC/DESC + * directions, and null ordering. The two {@link InternalRowWrapper} instances are allocated once + * and reused — {@code wrap()} just updates an internal reference. + */ + private static Comparator<InternalRow> buildComparator( + Schema mergeReadSchema, SortOrder sortOrder) { + StructType sparkSchema = SparkSchemaUtil.convert(mergeReadSchema); + Comparator<StructLike> keyComparator = + SortOrderComparators.forSchema(mergeReadSchema, sortOrder); + InternalRowWrapper left = new InternalRowWrapper(sparkSchema, mergeReadSchema.asStruct()); + InternalRowWrapper right = new InternalRowWrapper(sparkSchema, mergeReadSchema.asStruct()); + return (r1, r2) -> keyComparator.compare(left.wrap(r1), right.wrap(r2)); + } + + /** + * Returns a {@link ProjectingInternalRow} that remaps columns from the wider merge schema back to + * the requested projection, or {@code null} if no extra columns were added. + */ + private static ProjectingInternalRow buildProjectingRow(Schema projection, Schema mergeSchema) { + if (projection.columns().size() == mergeSchema.columns().size()) { + return null; + } + + List<Types.NestedField> mergeColumns = mergeSchema.columns(); + List<Object> positions = Lists.newArrayListWithCapacity(projection.columns().size()); + + for (int i = 0; i < projection.columns().size(); i++) { + int fieldId = projection.columns().get(i).fieldId(); + boolean found = false; + for (int j = 0; j < mergeColumns.size(); j++) { + if (mergeColumns.get(j).fieldId() == fieldId) { + positions.add(j); + found = true; + break; + } + } + Preconditions.checkState( + found, "Projection field id=%s not found in merge read schema — this is a bug", fieldId); + } + + StructType sparkSchema = SparkSchemaUtil.convert(projection); + return new ProjectingInternalRow(sparkSchema, JavaConverters.asScala(positions).toIndexedSeq()); + } + + /** + * Returns the schema to use when reading each file. This is the requested {@code projection} + * augmented with any sort key columns that are not already present, so the merge comparator can + * access every sort key field regardless of what Spark projected. + */ + private static Schema mergeReadSchema(Schema projection, SortOrder sortOrder, Table table) { + Schema tableSchema = table.schema(); + List<Types.NestedField> missingFields = Lists.newArrayList(); + + for (SortField sortField : sortOrder.fields()) { Review Comment: Good catch. I added a test `mergeWithSortOrderReferencingSameColumnMultipleTimes()` to reproduce this and fixed it by checking for duplicates for mergeReadSchema. -- 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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