[GitHub] [iceberg] kbendick commented on a change in pull request #4060: Flink: DataIteratorBatcher that converts iterator of T to iterator of…

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

kbendick commented on a change in pull request #4060:
URL: https://github.com/apache/iceberg/pull/4060#discussion_r809659361



##########
File path: flink/v1.14/flink/src/main/java/org/apache/iceberg/flink/source/DataIterator.java
##########
@@ -41,16 +42,59 @@
   private final FileScanTaskReader<T> fileScanTaskReader;
 
   private final InputFilesDecryptor inputFilesDecryptor;
+  private final CombinedScanTask combinedTask;
+
   private Iterator<FileScanTask> tasks;
   private CloseableIterator<T> currentIterator;
+  private int fileOffset;
+  private long recordOffset;
 
   public DataIterator(FileScanTaskReader<T> fileScanTaskReader, CombinedScanTask task,
                       FileIO io, EncryptionManager encryption) {
     this.fileScanTaskReader = fileScanTaskReader;
 
     this.inputFilesDecryptor = new InputFilesDecryptor(task, io, encryption);
+    this.combinedTask = task;
+
     this.tasks = task.files().iterator();
     this.currentIterator = CloseableIterator.empty();
+
+    // fileOffset starts at -1 because we started
+    // from an empty iterator that is not from the split files.
+    this.fileOffset = -1;
+    // record offset points to the record that next() should return when called
+    this.recordOffset = 0L;
+  }
+
+  /**
+   * (startingFileOffset, startingRecordOffset) points to the next row that reader should resume from.
+   * E.g., if the seek position is (file=0, record=1), seek moves the iterator position to the 2nd row
+   * in file 0. When next() is called after seek, 2nd row from file 0 should be returned.
+   */
+  public void seek(int startingFileOffset, long startingRecordOffset) {
+    Preconditions.checkState(fileOffset == -1,
+        "Seek should be called before any other iterator actions");
+    // skip files
+    Preconditions.checkState(startingFileOffset < combinedTask.files().size(),
+        "Invalid startingFileOffset %d for CombinedScanTask with %d files: %s",
+        startingFileOffset, combinedTask.files().size(), combinedTask);
+    for (long i = 0L; i < startingFileOffset; ++i) {
+      tasks.next();
+    }
+
+    updateCurrentIterator();
+    // skip records within the file
+    for (long i = 0; i < startingRecordOffset; ++i) {
+      if (currentFileHasNext() && hasNext()) {
+        next();
+      } else {
+        throw new IllegalStateException(String.format("Invalid startingRecordOffset %d for file %d " +
+            "from CombinedScanTask: %s", startingRecordOffset, startingFileOffset, combinedTask));

Review comment:
       Nit when you update the exception language:
   
   Is it possible to move the arguments around so you don’t have to use `+` on two strings inside of String.format? Not the end of the world but if you’re updating that spot already, it’s something to consider.




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