[GitHub] [iceberg] Fokko commented on a change in pull request #1972: First version of the Iceberg sink for Apache Beam

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

Fokko commented on a change in pull request #1972:
URL: https://github.com/apache/iceberg/pull/1972#discussion_r550996360



##########
File path: beam/src/main/java/org/apache/iceberg/beam/IcebergIO.java
##########
@@ -0,0 +1,119 @@
+/*
+ * 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.beam;
+
+import org.apache.beam.sdk.io.WriteFilesResult;
+import org.apache.beam.sdk.transforms.Combine;
+import org.apache.beam.sdk.values.KV;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.iceberg.AppendFiles;
+import org.apache.iceberg.DataFiles;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.Snapshot;
+import org.apache.iceberg.Table;
+import org.apache.iceberg.catalog.TableIdentifier;
+import org.apache.iceberg.exceptions.NoSuchTableException;
+import org.apache.iceberg.hive.HiveCatalog;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
+import org.apache.iceberg.relocated.com.google.common.collect.Iterables;
+
+import java.util.LinkedList;
+import java.util.List;
+
+
+public class IcebergIO {
+
+  private IcebergIO() {
+  }
+
+  static void write(TableIdentifier table,
+                    Schema schema,
+                    String hiveMetastoreUrl,
+                    WriteFilesResult<Void> resultFiles) {
+    resultFiles.getPerDestinationOutputFilenames().apply(
+        Combine.globally(new FileCombiner(table, schema, hiveMetastoreUrl)).withoutDefaults()
+    );
+  }
+
+  private static class FileCombiner extends Combine.CombineFn<KV<Void, String>, List<String>, Snapshot> {
+    private final TableIdentifier tableIdentifier;
+    private final Schema schema;
+    private final String hiveMetastoreUrl;
+
+    FileCombiner(TableIdentifier table, Schema schema, String hiveMetastoreUrl) {
+      this.tableIdentifier = table;
+      this.schema = schema;
+      this.hiveMetastoreUrl = hiveMetastoreUrl;
+    }
+
+    @Override
+    public List<String> createAccumulator() {
+      return new LinkedList<>();
+    }
+
+    @Override
+    public List<String> addInput(List<String> mutableAccumulator, KV<Void, String> input) {
+      mutableAccumulator.add(input.getValue());
+      return mutableAccumulator;
+    }
+
+    @Override
+    public List<String> mergeAccumulators(Iterable<List<String>> accumulators) {
+      return ImmutableList.copyOf(Iterables.concat(accumulators));
+    }
+
+    @Override
+    public Snapshot extractOutput(List<String> accumulator) {
+      try (HiveCatalog catalog = new HiveCatalog(
+          HiveCatalog.DEFAULT_NAME,
+          this.hiveMetastoreUrl,
+          1,
+          new Configuration()
+      )) {
+        Table table;
+        try {
+          table = catalog.loadTable(this.tableIdentifier);
+        } catch (NoSuchTableException e) {
+          // If it doesn't exist, we just create the table
+          table = catalog.createTable(this.tableIdentifier, schema);
+        }
+
+        // In case the schema has changed
+        if (table.schema() != this.schema) {
+          table.updateSchema().unionByNameWith(this.schema).commit();
+        }
+
+        // Append the new files
+        final AppendFiles app = table.newAppend();
+        // We need to get the statistics, not easy to get them through Beam

Review comment:
       Avro is a first-class citizen in Beam, this is more or less the equivalent of the InternalRow of Spark. We could replace the AvroIO with an IcebergIO, but this feels like reinventing the wheel to me. Then we still need to current logic of doing the commits. So, let's keep this option open for now.




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