alexeykudinkin commented on code in PR #5627: URL: https://github.com/apache/hudi/pull/5627#discussion_r910521355
########## hudi-common/src/main/java/org/apache/hudi/common/model/HoodieMerge.java: ########## @@ -0,0 +1,38 @@ +/* + * 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.avro.Schema; +import org.apache.hudi.common.util.Option; + +import java.io.IOException; +import java.io.Serializable; +import java.util.Properties; + +/** + * HoodieMerge defines how to merge two records. It is a stateless component. + * It can implement the merging logic of HoodieRecord of different engines + * and avoid the performance consumption caused by the serialization/deserialization of Avro payload. + */ +public interface HoodieMerge extends Serializable { Review Comment: "Merge" by itself is a very opaque term and when we call it `HoodieMerge` w/o contextualizing it it becomes hard to understand what it actually relates to. I'd suggest to instead be a little more verbose in the name to make sure it's very clear what this component is intended to do, for ex something like `HoodieRecordMergingEngine` ########## hudi-common/src/main/java/org/apache/hudi/common/model/HoodieMerge.java: ########## @@ -0,0 +1,38 @@ +/* + * 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.avro.Schema; +import org.apache.hudi.common.util.Option; + +import java.io.IOException; +import java.io.Serializable; +import java.util.Properties; + +/** + * HoodieMerge defines how to merge two records. It is a stateless component. + * It can implement the merging logic of HoodieRecord of different engines + * and avoid the performance consumption caused by the serialization/deserialization of Avro payload. + */ +public interface HoodieMerge extends Serializable { + + HoodieRecord preCombine(HoodieRecord older, HoodieRecord newer); Review Comment: And for us to actually be able to do that we have to enforce following properties onto the `merge` implementations: - It'd be [associative operation](https://en.wikipedia.org/wiki/Associative_property): `f(a, f(b, c)) = f(f(a, b), c)` (which we can translate as having 3 versions A, B, C of the single record, both orders of operations applications have to yield the same result) ########## hudi-common/src/main/java/org/apache/hudi/common/model/HoodieMerge.java: ########## @@ -0,0 +1,38 @@ +/* + * 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.avro.Schema; +import org.apache.hudi.common.util.Option; + +import java.io.IOException; +import java.io.Serializable; +import java.util.Properties; + +/** + * HoodieMerge defines how to merge two records. It is a stateless component. + * It can implement the merging logic of HoodieRecord of different engines + * and avoid the performance consumption caused by the serialization/deserialization of Avro payload. + */ +public interface HoodieMerge extends Serializable { + + HoodieRecord preCombine(HoodieRecord older, HoodieRecord newer); Review Comment: So, historically, this has been 2 different methods with (potentially) different semantics: - `preCombine` is de-duplicating the input batch (before inserting it into the table - `combineAndGet` is used to merge persisted version with the incoming (that could have been previously de-duplicated I also don't see a reason for us to get hung up on this historical context and we should try to unify these historically (potentially) divergent methods into 1 providing a single avenue of merging records either inside a batch (when de-duping) or when combining persisted one with the incoming. -- This is an automated message from the Apache Git Service. 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