stevenzwu commented on code in PR #4744: URL: https://github.com/apache/iceberg/pull/4744#discussion_r884027693
########## core/src/main/java/org/apache/iceberg/BaseIncrementalAppendScan.java: ########## @@ -0,0 +1,179 @@ +/* + * 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; + +import java.util.List; +import java.util.Set; +import org.apache.iceberg.events.IncrementalScanEvent; +import org.apache.iceberg.events.Listeners; +import org.apache.iceberg.io.CloseableIterable; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.apache.iceberg.relocated.com.google.common.collect.FluentIterable; +import org.apache.iceberg.relocated.com.google.common.collect.Iterables; +import org.apache.iceberg.relocated.com.google.common.collect.Lists; +import org.apache.iceberg.relocated.com.google.common.collect.Sets; +import org.apache.iceberg.util.SnapshotUtil; +import org.apache.iceberg.util.TableScanUtil; + +class BaseIncrementalAppendScan extends BaseScan<IncrementalAppendScan> implements IncrementalAppendScan { + + BaseIncrementalAppendScan(TableOperations ops, Table table) { + this(ops, table, table.schema(), new TableScanContext()); + } + + BaseIncrementalAppendScan(TableOperations ops, Table table, Schema schema, TableScanContext context) { + super(ops, table, schema, context); + } + + @Override + protected IncrementalAppendScan newRefinedScan( + TableOperations newOps, Table newTable, Schema newSchema, TableScanContext newContext) { + return new BaseIncrementalAppendScan(newOps, newTable, newSchema, newContext); + } + + @Override + public IncrementalAppendScan fromSnapshotInclusive(long fromSnapshotId) { Review Comment: In Kafka source case, users can pin the read Avro schema. As long as schema evolution is backward compatible (like an extra column), this is fine. If users don't pin read schema, only Avro GenericRecord is possible with a schema registry. Kafka record contains a schema id or fingerprint that consumers can use to look up schema from registry. SpecificRecord implicitly pinned the read schema to the schema used to generate the SpecificRecord code. Similarly with Flink Iceberg source (as an example), users can set read/projected schema. Then the Flink reader should emit `RowData` with fields only from the pinned read schema. if users don't pin the read schema, current table schema is used as read schema. Read schema stays the same until the next time the Flink job is redeployed and then read schema is refreshed to the table schema again. If a mandatory field is deleted (incompatible schema change), then consumer apps may be broken if the deleted column is accessed. Here is probably a more tricky scenario that would fail - users don't pin read schema - a new required column is added to Iceberg table schema - read scanned some old snapshots/data where is new required column is not present Either users should pin read schema or users need to make sure not to scan old data where current table is incompatible. I would think adding a required column is also an incompatible schema evolution as it is incompatible to older data. cc @rdblue @kbendick @Fokko for more inputs -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
