[GitHub] [hudi] alvarolemos commented on a diff in pull request #4724: [HUDI-2815] add partial overwrite payload to support partial overwrit…

[GitBox <gi...@apache.org>]

alvarolemos commented on code in PR #4724:
URL: https://github.com/apache/hudi/pull/4724#discussion_r850644656


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hudi-common/src/main/java/org/apache/hudi/common/model/PartialOverwriteWithLatestAvroPayload.java:
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@@ -0,0 +1,133 @@
+/*
+ * 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.model;
+
+import org.apache.hudi.common.util.Option;
+
+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 java.util.Properties;
+import java.util.function.BiFunction;
+
+import static org.apache.hudi.avro.HoodieAvroUtils.bytesToAvro;
+
+/**
+ * The only difference with {@link OverwriteNonDefaultsWithLatestAvroPayload} is that it supports
+ * merging the latest non-null partial fields with the old record instead of replacing the whole record.
+ * And merging the non-null fields during preCombine multiple records with same record key instead of choosing the latest record based on ordering field.
+ *
+ * <p> Regarding #combineAndGetUpdateValue, Assuming a {@link GenericRecord} has row schema: (f0 int , f1 int, f2 int).
+ * The first record value is: (1, 2, 3), the second record value is: (4, 5, null) with the field f2 value as null.
+ * Calling the #combineAndGetUpdateValue method of the two records returns record: (4, 5, 3).
+ * Note that field f2 value is ignored because it is null. </p>
+ *
+ * <p> Regarding #preCombine, Assuming a {@link GenericRecord} has row schema: (f0 int , f1 int, f2 int, o1 int),
+ * and initial two {@link PartialOverwriteWithLatestAvroPayload} with different ordering value.
+ * The first record value is (1, null, 1, 1) with the filed f1 value as null, the second value is: (2, 2, null, 2) with the f2 value as null.
+ * Calling the #preCombine method of the two records returns record: (2, 2, 1, 2).
+ * Note:
+ * <ol>
+ *   <li>the field f0 value is 2 because the ordering value of second record is bigger.</li>
+ *   <li>the filed f1 value is 2 because the f2 value of first record is null.</li>
+ *   <li>the filed f2 value is 1 because the f2 value of second record is null.</li>
+ *   <li>the filed o1 value is 2 because the ordering value of second record is bigger.</li>
+ * </ol>
+ *
+ * </p>
+ */
+public class PartialOverwriteWithLatestAvroPayload extends OverwriteWithLatestAvroPayload {
+
+  public PartialOverwriteWithLatestAvroPayload(GenericRecord record, Comparable orderingVal) {
+    super(record, orderingVal);
+  }
+
+  public PartialOverwriteWithLatestAvroPayload(Option<GenericRecord> record) {
+    super(record); // natural order
+  }
+
+  @Override
+  public Option<IndexedRecord> combineAndGetUpdateValue(IndexedRecord currentValue, Schema schema) throws IOException {
+    if (recordBytes.length == 0) {
+      return Option.empty();
+    }
+
+    GenericRecord incomingRecord = bytesToAvro(recordBytes, schema);
+    GenericRecord currentRecord = (GenericRecord) currentValue;
+    if (isDeleteRecord(incomingRecord)) {
+      return Option.empty();
+    }
+    return Option.of(overwriteWithNonNullValue(schema, currentRecord, incomingRecord));
+  }
+
+  @Override
+  public int compareTo(OverwriteWithLatestAvroPayload oldValue) {
+    return this.orderingVal.compareTo(oldValue.orderingVal);
+  }
+
+  @Override
+  public OverwriteWithLatestAvroPayload preCombine(OverwriteWithLatestAvroPayload oldValue, Properties properties, Schema schema) {
+    if (null == schema) {
+      // using default preCombine logic
+      return super.preCombine(oldValue);
+    }
+
+    try {
+      Option<IndexedRecord> incomingOption = this.getInsertValue(schema);
+      Option<IndexedRecord> oldRecordOption = oldValue.getInsertValue(schema);
+
+      if (incomingOption.isPresent() && oldRecordOption.isPresent()) {
+        boolean inComingRecordIsLatest = this.compareTo(oldValue) >= 0;
+        // ordering two records by ordering value
+        GenericRecord firstRecord = (GenericRecord) (inComingRecordIsLatest ? oldRecordOption.get() : incomingOption.get());
+        GenericRecord secondRecord = (GenericRecord) (inComingRecordIsLatest ? incomingOption.get() : oldRecordOption.get());
+        GenericRecord mergedRecord = overwriteWithNonNullValue(schema, firstRecord, secondRecord);
+        return new PartialOverwriteWithLatestAvroPayload(mergedRecord, inComingRecordIsLatest ? this.orderingVal : oldValue.orderingVal);
+      } else {
+        return super.preCombine(oldValue);
+      }
+    } catch (IOException e) {
+      return super.preCombine(oldValue);
+    }
+  }
+
+  private GenericRecord mergeRecord(Schema schema, GenericRecord first, GenericRecord second, BiFunction<Object, Object, Object> mergeFunc) {
+    schema.getFields().forEach(field -> {
+      Object firstValue = first.get(field.name());
+      Object secondValue = second.get(field.name());
+      first.put(field.name(), mergeFunc.apply(firstValue, secondValue));
+    });
+    return first;
+  }
+
+  /**
+   * Merge two records, the merged value of each filed will adopt the filed value from secondRecord if the value is not null, otherwise, adopt the filed value from firstRecord.
+   *
+   * @param schema record schema to loop fields
+   * @param firstRecord the base record need to be updated
+   * @param secondRecord the new record provide new field value
+   * @return merged records
+   */
+  private GenericRecord overwriteWithNonNullValue(Schema schema, GenericRecord firstRecord, GenericRecord secondRecord) {

Review Comment:
   @stayrascal,
   
   I really liked the idea of having a record payload that does partial merging. However, if I understood it correctly, what's proposed here is to do so in a very specific way: you're favoring the income record field's values, unless they are null (in which case, you would keep the existing one). I'm not saying this is not valuable, but that the idea of doing partial merging is so good that maybe we could have something more generic. I'm going to suggest a few changes in order to accomplish that:
   
   - Make `PartialOverwriteWithLatestAvroPayload` an abstract class
   - Instead of having `mergeFunc` as a parameter of the `mergeRecord` method, it could become an abstract method. This would lead to the removal of the `overwriteWithNonNullValue` method, which makes this implementation specific to your merging logic
   - For the original use case (partial merge favoring non-null values), implement the proposed abstract class and implement the `mergeFunc` method with what you have in `overwriteWithNonNullValue`: `(first, second) -> Objects.isNull(second) ? first : second`
   
   It's just an idea, that could make what you proposed useful for many more use cases. Hope this made sense, and thanks for bringing this idea!



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