core/src/main/java/org/apache/iceberg/BaseMetadataTable.java

/*
 * 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.io.FileIO;
import org.apache.iceberg.io.LocationProvider;
import org.apache.iceberg.relocated.com.google.common.collect.ImmutableMap;

/**
 * Base class for metadata tables.
 * <p>
 * Serializing and deserializing a metadata table object returns a read only implementation of the metadata table
 * using a {@link StaticTableOperations}. This way no Catalog related calls are needed when reading the table data after
 * deserialization.
 */
abstract class BaseMetadataTable implements Table, Serializable {
  private final PartitionSpec spec = PartitionSpec.unpartitioned();
  private final SortOrder sortOrder = SortOrder.unsorted();

  abstract Table table();

  @Override
  public FileIO io() {
    return table().io();
  }

  @Override
  public String location() {
    return table().location();
  }

  @Override
  public EncryptionManager encryption() {
    return table().encryption();
  }

  @Override
  public LocationProvider locationProvider() {
    return table().locationProvider();
  }

  @Override
  public void refresh() {
    table().refresh();
  }

  @Override
  public PartitionSpec spec() {
    return spec;
  }

  @Override
  public Map<Integer, PartitionSpec> specs() {
    return ImmutableMap.of(spec.specId(), spec);
  }

  @Override
  public SortOrder sortOrder() {
    return sortOrder;
  }

  @Override
  public Map<Integer, SortOrder> sortOrders() {
    return ImmutableMap.of(sortOrder.orderId(), sortOrder);
  }

  @Override
  public Map<String, String> properties() {
    return ImmutableMap.of();
  }

  @Override
  public Snapshot currentSnapshot() {
    return table().currentSnapshot();
  }

  @Override
  public Iterable<Snapshot> snapshots() {
    return table().snapshots();
  }

  @Override
  public Snapshot snapshot(long snapshotId) {
    return table().snapshot(snapshotId);
  }

  @Override
  public List<HistoryEntry> history() {
    return table().history();
  }

  @Override
  public UpdateSchema updateSchema() {
    throw new UnsupportedOperationException("Cannot update the schema of a metadata table");
  }

  @Override
  public UpdatePartitionSpec updateSpec() {
    throw new UnsupportedOperationException("Cannot update the partition spec of a metadata table");
  }

  @Override
  public UpdateProperties updateProperties() {
    throw new UnsupportedOperationException("Cannot update the properties of a metadata table");
  }

  @Override
  public ReplaceSortOrder replaceSortOrder() {
    throw new UnsupportedOperationException("Cannot update the sort order of a metadata table");
  }

  @Override
  public UpdateLocation updateLocation() {
    throw new UnsupportedOperationException("Cannot update the location of a metadata table");
  }

  @Override
  public AppendFiles newAppend() {
    throw new UnsupportedOperationException("Cannot append to a metadata table");
  }

  @Override
  public RewriteFiles newRewrite() {
    throw new UnsupportedOperationException("Cannot rewrite in a metadata table");
  }

  @Override
  public RewriteManifests rewriteManifests() {
    throw new UnsupportedOperationException("Cannot rewrite manifests in a metadata table");
  }

  @Override
  public OverwriteFiles newOverwrite() {
    throw new UnsupportedOperationException("Cannot overwrite in a metadata table");
  }

  @Override
  public RowDelta newRowDelta() {
    throw new UnsupportedOperationException("Cannot remove or replace rows in a metadata table");
  }

  @Override
  public ReplacePartitions newReplacePartitions() {
    throw new UnsupportedOperationException("Cannot replace partitions in a metadata table");
  }

  @Override
  public DeleteFiles newDelete() {
    throw new UnsupportedOperationException("Cannot delete from a metadata table");
  }

  @Override
  public ExpireSnapshots expireSnapshots() {
    throw new UnsupportedOperationException("Cannot expire snapshots from a metadata table");
  }

  @Override
  public Rollback rollback() {
    throw new UnsupportedOperationException("Cannot roll back a metadata table");
  }

  @Override
  public ManageSnapshots manageSnapshots() {
    throw new UnsupportedOperationException("Cannot manage snapshots in a metadata table");
  }

  @Override
  public Transaction newTransaction() {
    throw new UnsupportedOperationException("Cannot create transactions for a metadata table");
  }

  @Override
  public String toString() {
    return name();
  }

  abstract String metadataLocation();

  abstract MetadataTableType metadataTableType();

  final Object writeReplace() {
    return new TableProxy(io(), table().name(), name(), metadataLocation(), metadataTableType());
  }

  static class TableProxy implements Serializable {
    private FileIO io;
    private String baseTableName;
    private String metadataTableName;
    private String metadataLocation;
    private MetadataTableType type;

    TableProxy(FileIO io, String baseTableName, String metadataTableName, String metadataLocation,
               MetadataTableType type) {
      this.io = io;
      this.baseTableName = baseTableName;
      this.metadataTableName = metadataTableName;
      this.metadataLocation = metadataLocation;
      this.type = type;
    }

    /**
     * Returns a table with {@link StaticTableOperations} so after deserialization no Catalog related calls are
     * needed for accessing the table snapshot data.
     * @return The metadata Table object for reading the table data at the time of the serialization of the original
     *         object
     */
    private Object readResolve()  {
      TableOperations ops = new StaticTableOperations(metadataLocation, io);
      return MetadataTableUtils.createMetadataTableInstance(ops, baseTableName, metadataTableName, type);
    }
  }
}