[GitHub] [iceberg] kbendick commented on a change in pull request #1263: Add MicroBatch support in Iceberg Core

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

kbendick commented on a change in pull request #1263:
URL: https://github.com/apache/iceberg/pull/1263#discussion_r461726054



##########
File path: core/src/main/java/org/apache/iceberg/MicroBatches.java
##########
@@ -0,0 +1,255 @@
+/*
+ * 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.IOException;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+import org.apache.iceberg.io.CloseableIterable;
+import org.apache.iceberg.io.CloseableIterator;
+import org.apache.iceberg.io.FileIO;
+import org.apache.iceberg.relocated.com.google.common.base.Preconditions;
+import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList;
+import org.apache.iceberg.relocated.com.google.common.collect.Lists;
+import org.apache.iceberg.util.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class MicroBatches {
+  private MicroBatches() {
+  }
+
+  public static class MicroBatch {
+    private final long snapshotId;
+    private final int startFileIndex;
+    private final int endFileIndex;
+    private final long sizeInBytes;
+    private final List<FileScanTask> tasks;
+    private final boolean lastIndexOfSnapshot;
+
+    private MicroBatch(long snapshotId, int startFileIndex, int endFileIndex, long sizeInBytes,
+               List<FileScanTask> tasks, boolean lastIndexOfSnapshot) {
+      this.snapshotId = snapshotId;
+      this.startFileIndex = startFileIndex;
+      this.endFileIndex = endFileIndex;
+      this.sizeInBytes = sizeInBytes;
+      this.tasks = tasks;
+      this.lastIndexOfSnapshot = lastIndexOfSnapshot;
+    }
+
+    public long snapshotId() {
+      return snapshotId;
+    }
+
+    public int startFileIndex() {
+      return startFileIndex;
+    }
+
+    public int endFileIndex() {
+      return endFileIndex;
+    }
+
+    public long sizeInBytes() {
+      return sizeInBytes;
+    }
+
+    public List<FileScanTask> tasks() {
+      return tasks;
+    }
+
+    public boolean lastIndexOfSnapshot() {
+      return lastIndexOfSnapshot;
+    }
+  }
+
+  public static MicroBatchBuilder from(Snapshot snapshot, FileIO io) {
+    return new MicroBatchBuilder(snapshot, io);
+  }
+
+  public static class MicroBatchBuilder {
+    private static final Logger LOG = LoggerFactory.getLogger(MicroBatchBuilder.class);
+
+    private final Snapshot snapshot;
+    private final FileIO io;
+    private boolean caseSensitive;
+    private Map<Integer, PartitionSpec> specsById;
+
+    private MicroBatchBuilder(Snapshot snapshot, FileIO io) {
+      this.snapshot = snapshot;
+      this.io = io;
+      this.caseSensitive = true;
+    }
+
+    public MicroBatchBuilder caseSensitive(boolean sensitive) {
+      this.caseSensitive = sensitive;
+      return this;
+    }
+
+    public MicroBatchBuilder specsById(Map<Integer, PartitionSpec> specs) {
+      this.specsById = specs;
+      return this;
+    }
+
+    public MicroBatch generate(int startFileIndex, long targetSizeInBytes, boolean isStarting) {
+      Preconditions.checkArgument(startFileIndex >= 0, "startFileIndex is unexpectedly smaller than 0");

Review comment:
       Nit: The language on condition failure should match the next precondition check. `startFileIndex should be greater than or equal to zero` or something would make much more sense to me. 




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