stevenzwu commented on code in PR #4329: URL: https://github.com/apache/iceberg/pull/4329#discussion_r844348109
########## flink/v1.14/flink/src/main/java/org/apache/iceberg/flink/source/enumerator/ContinuousSplitPlannerImpl.java: ########## @@ -0,0 +1,160 @@ +/* + * 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.flink.source.enumerator; + +import java.util.Collections; +import java.util.List; +import java.util.Optional; +import java.util.concurrent.ExecutorService; +import org.apache.flink.annotation.Internal; +import org.apache.flink.annotation.VisibleForTesting; +import org.apache.iceberg.Snapshot; +import org.apache.iceberg.Table; +import org.apache.iceberg.flink.source.FlinkSplitPlanner; +import org.apache.iceberg.flink.source.ScanContext; +import org.apache.iceberg.flink.source.StreamingStartingStrategy; +import org.apache.iceberg.flink.source.split.IcebergSourceSplit; +import org.apache.iceberg.util.SnapshotUtil; +import org.apache.iceberg.util.ThreadPools; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +@Internal +public class ContinuousSplitPlannerImpl implements ContinuousSplitPlanner { + private static final Logger LOG = LoggerFactory.getLogger(ContinuousSplitPlannerImpl.class); + + private final Table table; + private final ScanContext scanContext; + private final ExecutorService workerPool; + + public ContinuousSplitPlannerImpl(Table table, ScanContext scanContext, String threadPoolName) { + this.table = table; + this.scanContext = scanContext; + this.workerPool = ThreadPools.newWorkerPool( + "iceberg-plan-worker-pool-" + threadPoolName, scanContext.planParallelism()); + } + + @Override + public ContinuousEnumerationResult planSplits(IcebergEnumeratorPosition lastPosition) { + table.refresh(); + if (lastPosition != null) { + return discoverIncrementalSplits(lastPosition); + } else { + return discoverInitialSplits(); + } + } + + /** + * Discover incremental changes between @{code lastPosition} and current table snapshot + */ + private ContinuousEnumerationResult discoverIncrementalSplits(IcebergEnumeratorPosition lastPosition) { + // incremental discovery mode + Snapshot currentSnapshot = table.currentSnapshot(); + if (currentSnapshot.snapshotId() == lastPosition.endSnapshotId()) { + LOG.info("Current table snapshot is already enumerated: {}", currentSnapshot.snapshotId()); + return new ContinuousEnumerationResult(Collections.emptyList(), lastPosition); + } else { + ScanContext incrementalScan = scanContext + .copyWithAppendsBetween(lastPosition.endSnapshotId(), currentSnapshot.snapshotId()); + LOG.info("Incremental scan: startSnapshotId = {}, endSnapshotId = {}", + incrementalScan.startSnapshotId(), incrementalScan.endSnapshotId()); + List<IcebergSourceSplit> splits = FlinkSplitPlanner.planIcebergSourceSplits(table, incrementalScan, workerPool); + IcebergEnumeratorPosition position = IcebergEnumeratorPosition.builder() + .startSnapshotId(lastPosition.endSnapshotId()) + .startSnapshotTimestampMs(lastPosition.endSnapshotTimestampMs()) + .endSnapshotId(currentSnapshot.snapshotId()) + .endSnapshotTimestampMs(currentSnapshot.timestampMillis()) + .build(); + LOG.info("Discovered {} splits from incremental scan: {}", splits.size(), position); + return new ContinuousEnumerationResult(splits, position); + } + } + + /** + * Discovery initial set of splits based on {@link StreamingStartingStrategy}. + * + * <li>{@link ContinuousEnumerationResult#splits()} should contain initial splits + * discovered from table scan for {@link StreamingStartingStrategy#TABLE_SCAN_THEN_INCREMENTAL}. + * For all other strategies, splits collection should be empty. + * <li>{@link ContinuousEnumerationResult#position()} points to the starting position + * for the next incremental split discovery with exclusive behavior. Meaning files committed + * by the snapshot from the position in {@code ContinuousEnumerationResult} won't be included + * in the next incremental scan. + */ + private ContinuousEnumerationResult discoverInitialSplits() { + Optional<Snapshot> startSnapshotOptional = getStartSnapshot(table, scanContext); + if (!startSnapshotOptional.isPresent()) { + // set IcebergEnumeratorPosition to null in this case + return new ContinuousEnumerationResult(Collections.emptyList(), null); + } Review Comment: In a sync meeting with @rdblue , we agreed on two things 1. The starting snapshot should be inclusive. This is consistent with the behavior as Kafka source. It is also consistent with the empty table behavior below. I will rename the enum to `INCREMENTAL_FROM_...`, which hopefully clarify the inclusive behavior. 2. Earliest and latest start snapshot should work with empty table (all future snapshots should be included). This is original point from @yittg in this thread. I looked into the IncrementalDataTableScan and SnapshotUtil. To achieve the above behavior, we can make fromSnapshotId nullable (not primitive) in TableScan . ```java TableScan appendsBetween(long->Long fromSnapshotId, long toSnapshotId); ``` 1. We can just pass in starting snapshot's parent snapshotId as the fromSnapshotId (could be null) 2. The earliest or latest start strategy for an empty table would just set the fromSnapshotId to null. This method from SnapshotUtil already handles null fromSnapshotId ```java private static List<Snapshot> snapshotsWithin(Table table, Long fromSnapshotId, long toSnapshotId) ``` **It is source compatible (as boxing happens automatically), but not binary compatible**. Is that acceptable? cc @rdblue @openinx -- 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. 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