jojochuang commented on code in PR #8912:
URL: https://github.com/apache/ozone/pull/8912#discussion_r2326024846
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hadoop-hdds/rocksdb-checkpoint-differ/src/main/java/org/apache/ozone/rocksdb/util/SstFileSetReader.java:
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@@ -233,70 +236,149 @@ public String next() {
}
}
- private abstract static class MultipleSstFileIterator<T> implements
ClosableIterator<T> {
+ /**
+ * A wrapper class that holds an iterator and its current value for heap
operations.
+ */
+ private static class HeapEntryWithFileIdx<T extends Comparable<T>>
+ implements Comparable<HeapEntryWithFileIdx<T>> {
+ private final ClosableIterator<T> iterator;
+ private T currentKey;
+ // To ensure stable ordering for identical keys
+ private final int fileIndex;
+
+ HeapEntryWithFileIdx(ClosableIterator<T> iterator, int fileIndex) {
+ this.iterator = iterator;
+ this.fileIndex = fileIndex;
+ advance();
+ }
+
+ void close() {
+ iterator.close();
+ }
+
+ boolean advance() {
+ if (iterator.hasNext()) {
+ currentKey = iterator.next();
+ return true;
+ } else {
+ currentKey = null;
+ return false;
+ }
+ }
+
+ T getCurrentKey() {
+ return currentKey;
+ }
+
+ @Override
+ public int compareTo(@Nonnull HeapEntryWithFileIdx<T> other) {
+ if (this.currentKey == null && other.currentKey == null) {
+ return 0;
+ }
+ if (this.currentKey == null) {
+ return 1;
+ }
+ if (other.currentKey == null) {
+ return -1;
+ }
+
+ int result = this.currentKey.compareTo(other.currentKey);
+ if (result == 0) {
+ // For identical keys, prefer the one from the file with the higher
index
+ return Integer.compare(other.fileIndex, this.fileIndex);
+ }
+ return result;
+ }
+
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj) {
+ return true;
+ }
+ if (obj == null || getClass() != obj.getClass()) {
+ return false;
+ }
+
+ HeapEntryWithFileIdx<T> other = (HeapEntryWithFileIdx<T>) obj;
+ return compareTo(other) == 0;
+ }
- private final Iterator<String> fileNameIterator;
+ @Override
+ public int hashCode() {
+ return Objects.hash(iterator, currentKey, fileIndex);
+ }
+ }
- private String currentFile;
- private ClosableIterator<T> currentFileIterator;
+ private abstract static class MultipleSstFileIterator<T extends
Comparable<T>> implements ClosableIterator<T> {
Review Comment:
The MultipleSstFileIterator class is an abstract base for iterating over
multiple SST files. It uses a PriorityQueue to merge keys from all files in
sorted order. Each file's iterator is wrapped in a HeapEntryWithFileIdx object,
which ensures stable ordering for identical keys by considering the file index.
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