[GitHub] [iceberg] rdblue commented on a change in pull request #2403: Core: Add SerializedTable and SerializedMetadataTable

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

rdblue commented on a change in pull request #2403:
URL: https://github.com/apache/iceberg/pull/2403#discussion_r606535048



##########
File path: core/src/main/java/org/apache/iceberg/SerializedTable.java
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@@ -0,0 +1,312 @@
+/*
+ * 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.io.Serializable;
+import java.util.List;
+import java.util.Map;
+import org.apache.iceberg.encryption.EncryptionManager;
+import org.apache.iceberg.hadoop.HadoopFileIO;
+import org.apache.iceberg.hadoop.SerializedConfiguration;
+import org.apache.iceberg.io.FileIO;
+import org.apache.iceberg.io.LocationProvider;
+import org.apache.iceberg.util.SerializableMap;
+
+/**
+ * A read-only serializable table implementation that can be sent to other nodes.
+ * <p>
+ * While this class captures the metadata file location that can be used to load the full table
+ * metadata, it also serializes directly things like properties, schema, spec, sort order
+ * to avoid reading the metadata file from other nodes to access frequently needed metadata.
+ * <p>
+ * <em>Note:</em> loading the full metadata from a large number of nodes can overwhelm the storage.
+ */
+public class SerializedTable implements Table, Serializable {
+  private final String name;
+  private final String location;
+  private final String metadataFileLocation;
+  private final Map<String, String> properties;
+  private final String schemaAsJson;
+  private final String specAsJson;
+  private final String sortOrderAsJson;
+  private final FileIO io;
+  private final EncryptionManager encryption;
+  private final LocationProvider locationProvider;
+
+  private transient volatile Table lazyTable = null;
+  private transient volatile Schema lazySchema = null;
+  private transient volatile PartitionSpec lazySpec = null;
+  private transient volatile SortOrder lazySortOrder = null;
+
+  public SerializedTable(Table table) {
+    this.name = table.name();
+    this.location = table.location();
+    this.metadataFileLocation = metadataFileLocation(table);
+    this.properties = SerializableMap.copyOf(table.properties());
+    this.schemaAsJson = SchemaParser.toJson(table.schema());
+    this.specAsJson = PartitionSpecParser.toJson(table.spec());
+    this.sortOrderAsJson = SortOrderParser.toJson(table.sortOrder());
+    this.io = fileIO(table);
+    this.encryption = table.encryption();
+    this.locationProvider = table.locationProvider();
+  }
+
+  private String metadataFileLocation(Table table) {
+    if (table instanceof HasTableOperations) {
+      TableOperations ops = ((HasTableOperations) table).operations();
+      return ops.current().metadataFileLocation();
+    } else {
+      return null;
+    }
+  }
+
+  private FileIO fileIO(Table table) {

Review comment:
       I don't think that we should change the contract for dynamically loaded classes. If a user chooses to use Kryo and a dynamically loaded component, it is their responsibility to make sure the two are compatible. We just need to make sure that Iceberg-supplied classes work with Kryo.




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