the-other-tim-brown commented on code in PR #18098: URL: https://github.com/apache/hudi/pull/18098#discussion_r2957154664
########## hudi-spark-datasource/hudi-spark-common/src/main/scala/org/apache/spark/sql/hudi/blob/BatchedBlobReader.scala: ########## @@ -0,0 +1,732 @@ +/* + * 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.spark.sql.hudi.blob + +import org.apache.hudi.HoodieSparkUtils.sparkAdapter +import org.apache.hudi.common.schema.{HoodieSchema, HoodieSchemaType} +import org.apache.hudi.io.SeekableDataInputStream +import org.apache.hudi.storage.{HoodieStorage, HoodieStorageUtils, StorageConfiguration, StoragePath} + +import org.apache.spark.rdd.RDD +import org.apache.spark.sql.{Dataset, Encoders, Row} +import org.apache.spark.sql.catalyst.InternalRow +import org.apache.spark.sql.catalyst.expressions.{GenericRowWithSchema, SpecificInternalRow} +import org.apache.spark.sql.types.{BinaryType, StructField, StructType} +import org.slf4j.LoggerFactory + +import scala.collection.mutable.ArrayBuffer + +/** + * Batched byte range reader that optimizes I/O by combining consecutive reads for out-of-line data. + * + * This reader analyzes sequences of read requests within a partition and merges + * consecutive or nearby reads into single I/O operations. This significantly reduces + * the number of seeks and reads when processing sorted data. + * + * <h3>Schema Requirement:</h3> + * The blob column must match the schema defined in {@link HoodieSchema.Blob}: + * <pre> + * struct { + * type: string // "inline" or "out_of_line" + * data: binary (nullable) // inline data (null for out_of_line) + * reference: struct (nullable) { // file reference (null for inline) + * external_path: string + * offset: long + * length: long + * managed: boolean + * } + * } + * </pre> + * + * <h3>Key Features:</h3> + * <ul> + * <li>Batches consecutive reads from the same file</li> + * <li>Configurable gap threshold for merging nearby reads</li> + * <li>Lookahead buffer to identify batch opportunities</li> + * <li>Preserves input row order in output</li> + * </ul> + * + * <h3>Usage Example:</h3> + * {{{ + * import org.apache.hudi.udf.BatchedByteRangeReader + * import org.apache.spark.sql.functions._ + * // Read a table with a blob column (e.g. image_data) + * val df = spark.read.format("hudi").load("/my_path").select("image_data", "record_id") + * + * // Read with batching (best when data is sorted by external_path, offset) + * val result = BatchedByteRangeReader.readBatched(df, structColName = "file_info") + * + * // Result has: image_data, record_id, data + * result.show() + * }}} + * + * <h3>Performance Tips:</h3> + * <ul> + * <li>Sort input by (blob.reference.external_path, blob.reference.offset) for maximum batching effectiveness</li> + * <li>Increase lookaheadSize for better batch detection (at cost of memory)</li> + * <li>Tune maxGapBytes based on your data access patterns</li> + * </ul> + * + * @param storage HoodieStorage instance for file I/O + * @param maxGapBytes Maximum gap between ranges to consider for batching (default: 4KB) + * @param lookaheadSize Number of rows to buffer for batch detection (default: 50) + */ +class BatchedBlobReader( + storage: HoodieStorage, + maxGapBytes: Int = 4096, + lookaheadSize: Int = 50) { + + private val logger = LoggerFactory.getLogger(classOf[BatchedBlobReader]) + + /** + * Process a partition iterator, batching consecutive reads. + * + * This method consumes the input iterator and produces an output iterator + * with each row containing the original data plus a "data" column with the + * bytes read from the file. + * + * @param rows Iterator of input rows with struct column + * @param structColIdx Index of the struct column in the row + * @param outputSchema Schema for output rows + * @param accessor Type class for accessing row fields + * @param builder Type class for building output rows + * @tparam R Row type (Row or InternalRow) + * @return Iterator of output rows with data column added + */ + def processPartition[R]( + rows: Iterator[R], + structColIdx: Int, + outputSchema: StructType) + (implicit accessor: RowAccessor[R], builder: RowBuilder[R]): Iterator[R] = { + + // Create buffered iterator for lookahead + val bufferedRows = rows.buffered + + // Result buffer to maintain order + val resultIterator = new Iterator[R] { + private var currentBatch: Iterator[R] = Iterator.empty + private var rowIndex = 0L + + override def hasNext: Boolean = { + if (currentBatch.hasNext) { + true + } else if (bufferedRows.hasNext) { + // Process next batch + currentBatch = processNextBatch() + currentBatch.hasNext + } else { + false + } + } + + override def next(): R = { + if (!hasNext) { + throw new NoSuchElementException("No more rows") + } + currentBatch.next() + } + + /** + * Collect and process the next batch of rows. + */ + private def processNextBatch(): Iterator[R] = { + // Collect up to lookaheadSize rows with their original indices + val batch = collectBatch() + + if (batch.isEmpty) { + Iterator.empty + } else { + // Partition the batch into three groups + val (inlineRows, outOfLineRows) = batch.partition(_.inlineBytes.isDefined) + val (wholeFileRows, rangeRows) = outOfLineRows.partition(_.length < 0) + + // Case 1: Inline — return bytes directly without I/O + val inlineResults = inlineRows.map { ri => Review Comment: Right but I think it's easy enough to add reader support in this task so might as well. -- This is an automated message from the Apache Git Service. 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