the-other-tim-brown commented on code in PR #13242: URL: https://github.com/apache/hudi/pull/13242#discussion_r2096231675
########## hudi-common/src/main/java/org/apache/hudi/common/table/read/EngineBasedMerger.java: ########## @@ -0,0 +1,194 @@ +/* + * 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.hudi.common.table.read; + +import org.apache.hudi.avro.AvroSchemaCache; +import org.apache.hudi.common.config.RecordMergeMode; +import org.apache.hudi.common.config.TypedProperties; +import org.apache.hudi.common.engine.HoodieReaderContext; +import org.apache.hudi.common.model.DefaultHoodieRecordPayload; +import org.apache.hudi.common.model.HoodieAvroRecord; +import org.apache.hudi.common.model.HoodieKey; +import org.apache.hudi.common.model.HoodieRecord; +import org.apache.hudi.common.model.HoodieRecordMerger; +import org.apache.hudi.common.model.OverwriteWithLatestAvroPayload; +import org.apache.hudi.common.table.HoodieTableConfig; +import org.apache.hudi.common.util.HoodieRecordUtils; +import org.apache.hudi.common.util.Option; +import org.apache.hudi.common.util.ValidationUtils; +import org.apache.hudi.common.util.collection.Pair; + +import org.apache.avro.Schema; +import org.apache.avro.generic.GenericRecord; +import org.apache.avro.generic.IndexedRecord; + +import java.io.IOException; +import java.util.Objects; + +import static org.apache.hudi.common.model.HoodieRecordMerger.PAYLOAD_BASED_MERGE_STRATEGY_UUID; + +/** + * Handles the logic for merging two records in an engine agnostic way. This allows the Hudi project to consolidate the merging logic and avoid deviation between engines. + * The class takes in {@link HoodieReaderContext<T>} for the engine specific operations such as fetching the value representing the event time when {@link RecordMergeMode#EVENT_TIME_ORDERING} is used. + * @param <T> The type of the engine's row + */ +public class EngineBasedMerger<T> { + private final HoodieReaderContext<T> readerContext; + private final RecordMergeMode recordMergeMode; + private final Option<HoodieRecordMerger> recordMerger; + private final Option<String> payloadClass; + private final Schema readerSchema; + private final TypedProperties props; + + public EngineBasedMerger(HoodieReaderContext<T> readerContext, RecordMergeMode recordMergeMode, HoodieTableConfig tableConfig, TypedProperties props) { + this.readerContext = readerContext; + this.readerSchema = AvroSchemaCache.intern(readerContext.getSchemaHandler().getRequiredSchema()); + this.recordMergeMode = recordMergeMode; + this.recordMerger = readerContext.getRecordMerger(); + if (recordMerger.isPresent() && recordMerger.get().getMergingStrategy().equals(PAYLOAD_BASED_MERGE_STRATEGY_UUID)) { + this.payloadClass = Option.of(tableConfig.getPayloadClass()); + } else { + this.payloadClass = Option.empty(); + } + this.props = props; + } + + BufferedRecord<T> merge(Option<BufferedRecord<T>> olderOption, + Option<BufferedRecord<T>> newerOption, + boolean enablePartialMerging) throws IOException { + if (olderOption.isEmpty()) { + return newerOption.orElseThrow(() -> new IllegalArgumentException("Both older and newer record are empty")); + } + if (newerOption.isEmpty()) { + return olderOption.orElseThrow(() -> new IllegalArgumentException("Both older and newer record are empty")); + } + BufferedRecord<T> older = olderOption.get(); + BufferedRecord<T> newer = newerOption.get(); + + if (enablePartialMerging) { + // TODO(HUDI-7843): decouple the merging logic from the merger + // and use the record merge mode to control how to merge partial updates + Option<Pair<HoodieRecord, Schema>> mergedRecord = recordMerger.get().partialMerge( + readerContext.constructHoodieRecord(older), + readerContext.getSchemaFromBufferRecord(older), + readerContext.constructHoodieRecord(newer), + readerContext.getSchemaFromBufferRecord(newer), + readerSchema, + props); + + return mergedRecord.map(combinedRecordAndSchema -> { + HoodieRecord<T> combinedRecord = combinedRecordAndSchema.getLeft(); + // If pre-combine returns existing record, no need to update it + if (combinedRecord.getData() != olderOption.map(BufferedRecord::getRecord).orElse(null)) { + return BufferedRecord.forRecordWithContext(combinedRecord, combinedRecordAndSchema.getRight(), readerContext, props); + } + return older; + }).orElseGet(() -> getLatestAsDeleteRecord(newer, older)); + } else { + switch (recordMergeMode) { + case COMMIT_TIME_ORDERING: + return newer; + case EVENT_TIME_ORDERING: + return getNewerRecordWithEventTimeOrdering(newer, older); + case CUSTOM: + default: + if (older.isDelete() || newer.isDelete()) { + // IMPORTANT: + // this is needed when the fallback HoodieAvroRecordMerger got used, the merger would + // return Option.empty when the new payload data is empty(a delete) and ignores its ordering value directly. + return getNewerRecordWithEventTimeOrdering(newer, older); + } + Option<BufferedRecord<T>> mergeResult; + if (payloadClass.isPresent()) { + Option<Pair<HoodieRecord, Schema>> mergedRecord = getMergedRecord(older, newer); + mergeResult = mergedRecord.map(combinedRecordAndSchema -> { + T record = readerContext.convertAvroRecord((IndexedRecord) combinedRecordAndSchema.getLeft().getData()); + return BufferedRecord.forConvertedRecord(record, combinedRecordAndSchema.getLeft(), combinedRecordAndSchema.getRight(), readerContext, props); + }); + } else { + Option<Pair<HoodieRecord, Schema>> mergedRecord = recordMerger.get().merge( + readerContext.constructHoodieRecord(older), readerContext.getSchemaFromBufferRecord(older), + readerContext.constructHoodieRecord(newer), readerContext.getSchemaFromBufferRecord(newer), props); + mergeResult = mergedRecord.map(combinedRecordAndSchema -> + BufferedRecord.forRecordWithContext((HoodieRecord<T>) combinedRecordAndSchema.getLeft(), + combinedRecordAndSchema.getRight(), readerContext, props)); + } + return mergeResult.orElseGet(() -> getLatestAsDeleteRecord(newer, older)); + } + } + } + + private static <T> BufferedRecord<T> getNewerRecordWithEventTimeOrdering(BufferedRecord<T> newer, BufferedRecord<T> older) { + if (newer.isCommitTimeOrderingDelete()) { + return newer; + } + if (older.isCommitTimeOrderingDelete()) { + return older; + } + Comparable newOrderingValue = newer.getOrderingValue(); + Comparable oldOrderingValue = older.getOrderingValue(); + return oldOrderingValue.compareTo(newOrderingValue) > 0 ? older : newer; + } + + private Option<Pair<HoodieRecord, Schema>> getMergedRecord(BufferedRecord<T> older, BufferedRecord<T> newer) throws IOException { + ValidationUtils.checkArgument(!Objects.equals(payloadClass.get(), OverwriteWithLatestAvroPayload.class.getCanonicalName()) + && !Objects.equals(payloadClass.get(), DefaultHoodieRecordPayload.class.getCanonicalName())); + HoodieRecord oldHoodieRecord = constructHoodieAvroRecord(readerContext, older); + HoodieRecord newHoodieRecord = constructHoodieAvroRecord(readerContext, newer); + return recordMerger.get().merge(oldHoodieRecord, getSchemaForAvroPayloadMerge(oldHoodieRecord, older), + newHoodieRecord, getSchemaForAvroPayloadMerge(newHoodieRecord, newer), props); + } + + private Schema getSchemaForAvroPayloadMerge(HoodieRecord record, BufferedRecord<T> bufferedRecord) throws IOException { + if (record.isDelete(readerSchema, props)) { + return readerSchema; + } + return readerContext.getSchemaFromBufferRecord(bufferedRecord); + } + + /** + * Constructs a new {@link HoodieAvroRecord} for payload based merging + * + * @param readerContext reader context + * @param bufferedRecord the provided engine specific record and its metadata + * @return A new instance of {@link HoodieRecord}. + */ + private HoodieRecord constructHoodieAvroRecord(HoodieReaderContext<T> readerContext, BufferedRecord<T> bufferedRecord) { + GenericRecord record = null; + if (bufferedRecord.getRecord() != null) { + Schema recordSchema = readerContext.getSchemaFromBufferRecord(bufferedRecord); + record = readerContext.convertToAvroRecord(bufferedRecord.getRecord(), recordSchema); + } + return new HoodieAvroRecord<>(new HoodieKey(bufferedRecord.getRecordKey(), null), HoodieRecordUtils.loadPayload(payloadClass.get(), record, bufferedRecord.getOrderingValue())); + } + + /** + * Picks the "latest" record based on the merger strategy and converts that to a delete by setting the `delete` flag. + * @param newer the newer record passed to the merge function + * @param older the older record passed to the merge function + * @return the latest record as a delete record + */ + private BufferedRecord<T> getLatestAsDeleteRecord(BufferedRecord<T> newer, BufferedRecord<T> older) { + if (recordMerger.map(merger -> merger.getMergingStrategy().equals(HoodieRecordMerger.COMMIT_TIME_BASED_MERGE_STRATEGY_UUID)).orElse(false)) { Review Comment: The issue here is that the mergers will return an empty option when there is a delete: https://github.com/apache/hudi/blob/master/hudi-client/hudi-spark-client/src/main/java/org/apache/hudi/HoodieSparkRecordMerger.java#L50 I think that this can cause some unexpected issues when using event time ordering since you will lose the ordering value that should be used when comparing to the next record. For example, consider a delete at T2 and then it is followed by an insert with T1, that insert should be ignored but how will we keep track of that when the output drops this context? -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
