ibessonov commented on code in PR #2161:
URL: https://github.com/apache/ignite-3/pull/2161#discussion_r1222663971
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modules/storage-page-memory/src/main/java/org/apache/ignite/internal/storage/pagememory/index/AbstractPageMemoryIndexStorage.java:
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@@ -192,6 +196,123 @@ public void finishCleanup() {
state.compareAndSet(StorageState.CLEANUP, StorageState.RUNNABLE);
}
+ /** Constant that represents the absence of value in {@link ScanCursor}. */
+ private static final IndexRowKey NO_INDEX_ROW = () -> null;
+
+ /**
+ * Cursor that always returns up-to-date next element.
+ *
+ * @param <R> Type of the returned value.
+ */
+ protected abstract class ScanCursor<R> implements PeekCursor<R> {
+ private final BplusTree<K, V> indexTree;
+
+ @Nullable
+ private Boolean hasNext;
+
+ @Nullable
+ private final K lower;
+
+ @Nullable
+ private V treeRow;
+
+ @Nullable
+ private V peekedRow = (V) NO_INDEX_ROW;
+
+ protected ScanCursor(@Nullable K lower, BplusTree<K, V> indexTree) {
+ this.lower = lower;
+ this.indexTree = indexTree;
+ }
+
+ /**
+ * Maps value from the index tree into the required result.
+ */
+ protected abstract R map(V value);
+
+ /**
+ * Check whether the passed value exceeds the upper bound for the scan.
+ */
+ protected abstract boolean halt(V value);
Review Comment:
"uppder boun"?
What's wrong with "halt", that's a common name for stopping something
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