aokolnychyi commented on a change in pull request #875: [WIP] Spark: Implement 
an action to rewrite manifests
URL: https://github.com/apache/incubator-iceberg/pull/875#discussion_r405050932
 
 

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 File path: spark/src/main/java/org/apache/iceberg/RewriteManifestsAction.java
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+/*
+ * 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 com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+import java.io.Serializable;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import java.util.function.Predicate;
+import java.util.function.Supplier;
+import java.util.stream.Collectors;
+import org.apache.hadoop.fs.Path;
+import org.apache.iceberg.exceptions.ValidationException;
+import org.apache.iceberg.hadoop.HadoopFileIO;
+import org.apache.iceberg.io.FileIO;
+import org.apache.iceberg.io.OutputFile;
+import org.apache.iceberg.util.BinPacking;
+import org.apache.iceberg.util.PropertyUtil;
+import org.apache.iceberg.util.Tasks;
+import org.apache.spark.api.java.JavaRDD;
+import org.apache.spark.api.java.JavaSparkContext;
+import org.apache.spark.api.java.function.FlatMapFunction;
+import org.apache.spark.api.java.function.FlatMapGroupsFunction;
+import org.apache.spark.api.java.function.MapFunction;
+import org.apache.spark.broadcast.Broadcast;
+import org.apache.spark.sql.Dataset;
+import org.apache.spark.sql.Encoder;
+import org.apache.spark.sql.Encoders;
+import org.apache.spark.sql.SparkSession;
+import org.apache.spark.sql.TypedColumn;
+import org.apache.spark.sql.expressions.Aggregator;
+import org.apache.spark.util.SerializableConfiguration;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+// TODO: concurrent modification of snapshotIdInheritanceEnabled or specs?
+public class RewriteManifestsAction
+    implements SnapshotUpdateAction<RewriteManifestsAction, 
RewriteManifestsActionResult> {
+
+  private static final Logger LOG = 
LoggerFactory.getLogger(RewriteManifestsAction.class);
+
+  private final SparkSession spark;
+  private final JavaSparkContext sparkContext;
+  private final Table table;
+  private final FileIO fileIO;
+  private final Map<Integer, PartitionSpec> specs;
+  private final Map<String, String> summary;
+  private final int defaultParallelism;
+  private final boolean snapshotIdInheritanceEnabled;
+  private final long targetManifestSizeBytes;
+
+  private final Encoder<ManifestFile> manifestEncoder = 
Encoders.javaSerialization(ManifestFile.class);
+  private final Encoder<Entry> entryEncoder = 
Encoders.javaSerialization(Entry.class);
+  private final Encoder<Bin> binEncoder = Encoders.bean(Bin.class);
+
+  private Predicate<ManifestFile> predicate = manifest -> true;
+  private String stagingLocation = null;
+
+  RewriteManifestsAction(SparkSession spark, Table table) {
+    this.spark = spark;
+    this.sparkContext = new JavaSparkContext(spark.sparkContext());
+    this.table = table;
+    this.specs = table.specs();
+    this.summary = Maps.newHashMap();
+    this.defaultParallelism = Integer.parseInt(
+        spark.conf().get("spark.default.parallelism", "200"));
+    this.snapshotIdInheritanceEnabled = PropertyUtil.propertyAsBoolean(
+        table.properties(),
+        TableProperties.SNAPSHOT_ID_INHERITANCE_ENABLED,
+        TableProperties.SNAPSHOT_ID_INHERITANCE_ENABLED_DEFAULT);
+    this.targetManifestSizeBytes = PropertyUtil.propertyAsLong(
+        table.properties(),
+        TableProperties.MANIFEST_TARGET_SIZE_BYTES,
+        TableProperties.MANIFEST_TARGET_SIZE_BYTES_DEFAULT);
+
+    if (table.io() instanceof HadoopFileIO) {
+      // we need to use Spark's SerializableConfiguration to avoid issues with 
Kryo serialization
+      SerializableConfiguration conf = new 
SerializableConfiguration(((HadoopFileIO) table.io()).conf());
+      fileIO = new HadoopFileIO(conf::value);
+    } else {
+      fileIO = table.io();
+    }
+  }
+
+  public RewriteManifestsAction rewriteIf(Predicate<ManifestFile> 
newPredicate) {
+    this.predicate = newPredicate;
+    return this;
+  }
+
+  public RewriteManifestsAction stagingLocation(String newStagingLocation) {
+    this.stagingLocation = newStagingLocation;
+    return this;
+  }
+
+  @Override
+  public RewriteManifestsAction set(String property, String value) {
+    summary.put(property, value);
+    return this;
+  }
+
+  @Override
+  public RewriteManifestsActionResult execute() {
+    Preconditions.checkArgument(stagingLocation != null, "Staging location 
must be set");
+
+    List<ManifestFile> matchingManifests = findMatchingManifests();
+    if (matchingManifests.isEmpty()) {
+      return null;
+    }
+
+    Broadcast<FileIO> io = sparkContext.broadcast(fileIO);
+
+    int parallelism = Math.min(matchingManifests.size(), defaultParallelism);
+    JavaRDD<ManifestFile> manifestRDD = 
sparkContext.parallelize(matchingManifests, parallelism);
+    Dataset<ManifestFile> manifestDS = spark.createDataset(manifestRDD.rdd(), 
manifestEncoder);
+    Dataset<Entry> manifestEntryDS = manifestDS.flatMap(toEntries(io, specs), 
entryEncoder);
+
+    try {
+      manifestEntryDS.cache();
+
+      long manifestEntrySizeBytes = 
computeManifestEntrySizeBytes(matchingManifests);
+      Map<Integer, List<PartitionMetadata>> metadataSizeSummary = 
computeMetadataSizeSummary(
+          manifestEntryDS,
+          manifestEntrySizeBytes);
 
 Review comment:
   Yes, we can definitely compute this part using metadata tables. However, we 
need to migrate the second part of this action (i.e. writing new manifests) to 
metadata tables as well. Otherwise, we will read the metadata twice and I think 
we want to avoid that. We need a typed `Dataset` and actual `DataFile` 
instances with `StructLike` objects as partitions. Assuming we are processing 
one partition spec at a time will probably help us as the partition struct will 
have a fixed type. 

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