[GitHub] [iceberg] jackye1995 commented on a diff in pull request #6449: WIP: Delta, Spark: Adding support for Migrating Delta Lake Table to Iceberg Table

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

jackye1995 commented on code in PR #6449:
URL: https://github.com/apache/iceberg/pull/6449#discussion_r1061725464


##########
delta-lake/src/main/java/org/apache/iceberg/delta/BaseMigrateDeltaLakeTableAction.java:
##########
@@ -0,0 +1,275 @@
+/*
+ * 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.delta;
+
+import io.delta.standalone.DeltaLog;
+import io.delta.standalone.VersionLog;
+import io.delta.standalone.actions.Action;
+import io.delta.standalone.actions.AddFile;
+import io.delta.standalone.actions.RemoveFile;
+import java.io.File;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.stream.Collectors;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.iceberg.AppendFiles;
+import org.apache.iceberg.DataFile;
+import org.apache.iceberg.DataFiles;
+import org.apache.iceberg.DeleteFiles;
+import org.apache.iceberg.FileFormat;
+import org.apache.iceberg.Metrics;
+import org.apache.iceberg.OverwriteFiles;
+import org.apache.iceberg.PartitionField;
+import org.apache.iceberg.PartitionSpec;
+import org.apache.iceberg.Schema;
+import org.apache.iceberg.Snapshot;
+import org.apache.iceberg.SnapshotSummary;
+import org.apache.iceberg.Table;
+import org.apache.iceberg.catalog.Catalog;
+import org.apache.iceberg.catalog.TableIdentifier;
+import org.apache.iceberg.delta.actions.BaseMigrateDeltaLakeTableActionResult;
+import org.apache.iceberg.delta.actions.MigrateDeltaLakeTable;
+import org.apache.iceberg.delta.utils.DeltaLakeDataTypeVisitor;
+import org.apache.iceberg.delta.utils.DeltaLakeTypeToType;
+import org.apache.iceberg.delta.utils.FileMetricsReader;
+import org.apache.iceberg.exceptions.ValidationException;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableMap;
+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.Maps;
+import org.apache.iceberg.types.Type;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Takes a Delta Lake table's location and attempts to transform it into an Iceberg table in the
+ * same location with a different identifier.
+ */
+public class BaseMigrateDeltaLakeTableAction implements MigrateDeltaLakeTable {
+
+  private static final Logger LOG = LoggerFactory.getLogger(BaseMigrateDeltaLakeTableAction.class);
+  private static final String parquetSuffix = ".parquet";
+  private static final String avroSuffix = ".avro";
+  private static final String orcSuffix = ".orc";
+  private final Map<String, String> additionalProperties = Maps.newHashMap();
+  private final DeltaLog deltaLog;
+  private final Catalog icebergCatalog;
+  private final String deltaTableLocation;
+  private final TableIdentifier newTableIdentifier;
+  private final Configuration hadoopConfiguration;
+
+  public BaseMigrateDeltaLakeTableAction(
+      Catalog icebergCatalog,
+      String deltaTableLocation,
+      TableIdentifier newTableIdentifier,
+      Configuration hadoopConfiguration) {
+    this.icebergCatalog = icebergCatalog;
+    this.deltaTableLocation = deltaTableLocation;
+    this.newTableIdentifier = newTableIdentifier;
+    this.hadoopConfiguration = hadoopConfiguration;
+    this.deltaLog = DeltaLog.forTable(this.hadoopConfiguration, this.deltaTableLocation);
+  }
+
+  @Override
+  public MigrateDeltaLakeTable tableProperties(Map<String, String> properties) {
+    additionalProperties.putAll(properties);
+    return this;
+  }
+
+  @Override
+  public Result execute() {
+    io.delta.standalone.Snapshot updatedSnapshot = deltaLog.update();
+    Schema schema = convertDeltaLakeSchema(updatedSnapshot.getMetadata().getSchema());
+    PartitionSpec partitionSpec = getPartitionSpecFromDeltaSnapshot(schema);
+    // TODO: check whether we need more info when initializing the table
+    Table icebergTable =
+        this.icebergCatalog.createTable(
+            newTableIdentifier,
+            schema,
+            partitionSpec,
+            destTableProperties(
+                updatedSnapshot, this.deltaTableLocation, this.additionalProperties));
+
+    copyFromDeltaLakeToIceberg(icebergTable, partitionSpec);
+
+    Snapshot snapshot = icebergTable.currentSnapshot();
+    long totalDataFiles =
+        Long.parseLong(snapshot.summary().get(SnapshotSummary.TOTAL_DATA_FILES_PROP));
+    LOG.info(
+        "Successfully loaded Iceberg metadata for {} files to {}",
+        totalDataFiles,
+        deltaTableLocation);
+    return new BaseMigrateDeltaLakeTableActionResult(totalDataFiles);
+  }
+
+  /** TODO: check the correctness for nested schema */
+  private Schema convertDeltaLakeSchema(io.delta.standalone.types.StructType deltaSchema) {
+    Type converted =
+        DeltaLakeDataTypeVisitor.visit(deltaSchema, new DeltaLakeTypeToType(deltaSchema));
+    return new Schema(converted.asNestedType().asStructType().fields());
+  }
+
+  private PartitionSpec getPartitionSpecFromDeltaSnapshot(Schema schema) {
+    List<String> partitionNames = deltaLog.snapshot().getMetadata().getPartitionColumns();
+    if (partitionNames.isEmpty()) {
+      return PartitionSpec.unpartitioned();
+    }
+
+    PartitionSpec.Builder builder = PartitionSpec.builderFor(schema);
+    for (String partitionName : partitionNames) {
+      builder.identity(partitionName);
+    }
+    return builder.build();
+  }
+
+  private void copyFromDeltaLakeToIceberg(Table table, PartitionSpec spec) {
+    Iterator<VersionLog> versionLogIterator =
+        deltaLog.getChanges(
+            0, // retrieve actions starting from the initial version
+            false); // not throw exception when data loss detected
+
+    while (versionLogIterator.hasNext()) {
+      VersionLog versionLog = versionLogIterator.next();

Review Comment:
   I think that could be an add-on feature later if there is such a need from community, but we don't need that now.



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