[GitHub] [iceberg] singhpk234 commented on a diff in pull request #5063: Core: Add MetadataLog metadata table

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

singhpk234 commented on code in PR #5063:
URL: https://github.com/apache/iceberg/pull/5063#discussion_r924038523


##########
core/src/main/java/org/apache/iceberg/MetadataLogTable.java:
##########
@@ -0,0 +1,113 @@
+/*
+ * 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.util.List;
+import java.util.function.Function;
+import org.apache.iceberg.io.CloseableIterable;
+import org.apache.iceberg.relocated.com.google.common.collect.Lists;
+import org.apache.iceberg.types.Types;
+import org.apache.iceberg.util.SnapshotUtil;
+
+public class MetadataLogTable extends BaseMetadataTable {
+
+  private static final Schema METADATA_LOG_SCHEMA = new Schema(
+      Types.NestedField.required(1, "timestamp_millis", Types.LongType.get()),
+      Types.NestedField.required(2, "file", Types.StringType.get()),
+      Types.NestedField.optional(3, "latest_snapshot_id", Types.LongType.get())
+  );
+
+  MetadataLogTable(TableOperations ops, Table table) {
+    this(ops, table, table.name() + ".metadata_log");
+  }
+
+  MetadataLogTable(TableOperations ops, Table table, String name) {
+    super(ops, table, name);
+  }
+
+  @Override
+  MetadataTableType metadataTableType() {
+    return MetadataTableType.METADATA_LOG;
+  }
+
+  @Override
+  public TableScan newScan() {
+    return new MetadataLogScan(operations(), table());
+  }
+
+  @Override
+  public Schema schema() {
+    return METADATA_LOG_SCHEMA;
+  }
+
+  private DataTask task(TableScan scan) {
+    TableOperations ops = operations();
+    List<TableMetadata.MetadataLogEntry> metadataLogEntries =
+        Lists.newArrayList(ops.current().previousFiles().listIterator());
+    metadataLogEntries.add(new TableMetadata.MetadataLogEntry(ops.current().lastUpdatedMillis(),
+        ops.current().metadataFileLocation()));
+    return StaticDataTask.of(
+        ops.io().newInputFile(ops.current().metadataFileLocation()),
+        schema(),
+        scan.schema(),
+        metadataLogEntries,
+        convertMetadataLogEntryFunc(table())
+    );
+  }
+
+  private class MetadataLogScan extends StaticTableScan {
+    MetadataLogScan(TableOperations ops, Table table) {
+      super(ops, table, METADATA_LOG_SCHEMA, MetadataTableType.METADATA_LOG, MetadataLogTable.this::task);
+    }
+
+    MetadataLogScan(TableOperations ops, Table table, TableScanContext context) {
+      super(ops, table, METADATA_LOG_SCHEMA, MetadataTableType.METADATA_LOG, MetadataLogTable.this::task, context);
+    }
+
+    @Override
+    protected TableScan newRefinedScan(TableOperations ops, Table table, Schema schema, TableScanContext context) {
+      return new MetadataLogScan(ops, table, context);
+    }
+
+    @Override
+    public CloseableIterable<FileScanTask> planFiles() {
+      return CloseableIterable.withNoopClose(MetadataLogTable.this.task(this));
+    }
+  }
+
+  private static Function<TableMetadata.MetadataLogEntry, StaticDataTask.Row> convertMetadataLogEntryFunc(Table table) {
+    return metadataLogEntry -> {
+      long latestSnapshotId;
+      try {
+        latestSnapshotId = SnapshotUtil.snapshotIdAsOfTime(table, metadataLogEntry.timestampMillis());
+      } catch (Exception e) {
+        // implies this metadata file was created at table creation
+        latestSnapshotId = -1;
+      }
+
+      return StaticDataTask.Row.of(
+          metadataLogEntry.timestampMillis() * 1000,
+          metadataLogEntry.file(),
+          // latest snapshot in this file corresponding to the log entry
+          latestSnapshotId == -1 ? null : latestSnapshotId

Review Comment:
   done, thanks !



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