[GitHub] [incubator-iceberg] aokolnychyi commented on a change in pull request #655: Add PartitionsTable for partition metadata

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

aokolnychyi commented on a change in pull request #655: Add PartitionsTable for partition metadata
URL: https://github.com/apache/incubator-iceberg/pull/655#discussion_r347950984
 
 

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 File path: core/src/main/java/org/apache/iceberg/PartitionsTable.java
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+/*
+ * 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 com.google.common.collect.Maps;
+import java.util.Map;
+import org.apache.iceberg.types.Types;
+import org.apache.iceberg.util.StructLikeWrapper;
+
+/**
+ * A {@link Table} implementation that exposes a table's partitions as rows.
+ */
+public class PartitionsTable extends BaseMetadataTable {
+
+  private final TableOperations ops;
+  private final Table table;
+  private final Schema schema;
+
+  public PartitionsTable(TableOperations ops, Table table) {
+    this.ops = ops;
+    this.table = table;
+    this.schema = new Schema(
+        Types.NestedField.required(1, "partition", table.spec().partitionType()),
+        Types.NestedField.required(2, "record_count", Types.LongType.get()),
+        Types.NestedField.required(3, "file_count", Types.IntegerType.get())
+    );
+  }
+
+  @Override
+  Table table() {
+    return table;
+  }
+
+  @Override
+  String metadataTableName() {
+    return "partitions";
+  }
+
+  @Override
+  public TableScan newScan() {
+    return new PartitionsScan();
+  }
+
+  @Override
+  public String location() {
+    return ops.current().file().location();
+  }
+
+  @Override
+  public Schema schema() {
+    return schema;
+  }
+
+  private DataTask task(TableScan scan) {
+    return StaticDataTask.of(
+        ops.current().file(),
+        partitions(table, scan.snapshot().snapshotId()),
+        PartitionsTable::convertPartition);
+  }
+
+  private static StaticDataTask.Row convertPartition(Partition partition) {
+    return StaticDataTask.Row.of(partition.key, partition.recordCount, partition.fileCount);
+  }
+
+  private static Iterable<Partition> partitions(Table table, Long snapshotId) {
+    PartitionSet partitions = new PartitionSet();
+    TableScan scan = table.newScan();
+
+    if (snapshotId != null) {
+      scan = scan.useSnapshot(snapshotId);
+    }
+
+    for (FileScanTask task : scan.planFiles()) {
+      partitions.get(task.file().partition()).update(task.file());
+    }
+
+    return partitions.all();
+  }
+
+  private class PartitionsScan extends StaticTableScan {
 
 Review comment:
   Is it a good idea to extend `StaticTableScan`? Would it be more efficient to run an aggregation query on the files metadata table to compute stats per partition?

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