Github user arunmahadevan commented on a diff in the pull request:
https://github.com/apache/storm/pull/1950#discussion_r123981715
--- Diff:
storm-core/src/jvm/org/apache/storm/state/BaseBinaryStateIterator.java ---
@@ -0,0 +1,162 @@
+package org.apache.storm.state;
+
+import com.google.common.collect.Iterators;
+import com.google.common.collect.PeekingIterator;
+import com.google.common.primitives.UnsignedBytes;
+
+import java.util.AbstractMap;
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.Map;
+import java.util.NoSuchElementException;
+import java.util.Set;
+import java.util.TreeSet;
+
+/**
+ * Base implementation of iterator over {@link KeyValueState} which is
based on binary type.
+ */
+public abstract class BaseBinaryStateIterator<K, V> implements
Iterator<Map.Entry<K, V>> {
+
+ private final PeekingIterator<Map.Entry<byte[], byte[]>>
pendingPrepareIterator;
+ private final PeekingIterator<Map.Entry<byte[], byte[]>>
pendingCommitIterator;
+ private final Set<byte[]> providedKeys;
+
+ private boolean firstLoad = true;
+ private PeekingIterator<Map.Entry<byte[], byte[]>> pendingIterator;
+ private PeekingIterator<Map.Entry<byte[], byte[]>> cachedResultIterator;
+
+ /**
+ * Constructor.
+ *
+ * @param pendingPrepareIterator The iterator of pendingPrepare
+ * @param pendingCommitIterator The iterator of pendingCommit
+ */
+ public BaseBinaryStateIterator(Iterator<Map.Entry<byte[], byte[]>>
pendingPrepareIterator,
+ Iterator<Map.Entry<byte[], byte[]>> pendingCommitIterator) {
+ this.pendingPrepareIterator =
Iterators.peekingIterator(pendingPrepareIterator);
+ this.pendingCommitIterator =
Iterators.peekingIterator(pendingCommitIterator);
+ this.providedKeys = new
TreeSet<>(UnsignedBytes.lexicographicalComparator());
+ }
+
+ @Override
+ public boolean hasNext() {
+ if (seekToAvailableEntry(pendingPrepareIterator)) {
+ pendingIterator = pendingPrepareIterator;
+ return true;
+ }
+
+ if (seekToAvailableEntry(pendingCommitIterator)) {
+ pendingIterator = pendingCommitIterator;
+ return true;
+ }
+
+
+ if (firstLoad) {
+ // load the first part of entries
+ fillCachedResultIterator();
+ firstLoad = false;
+ }
+
+ while (true) {
+ if (seekToAvailableEntry(cachedResultIterator)) {
+ pendingIterator = cachedResultIterator;
+ return true;
+ }
+
+ if (isEndOfDataFromStorage()) {
+ break;
+ }
+
+ fillCachedResultIterator();
+ }
+
+ pendingIterator = null;
+ return false;
+ }
+
+ private void fillCachedResultIterator() {
+ Iterator<Map.Entry<byte[], byte[]>> iterator =
loadChunkFromStateStorage();
+ if (iterator != null) {
+ cachedResultIterator = Iterators.peekingIterator(iterator);
+ } else {
+ cachedResultIterator = null;
+ }
+ }
+
+ @Override
+ public Map.Entry<K, V> next() {
+ if (!hasNext()) {
+ throw new NoSuchElementException();
+ }
+
+ Map.Entry<byte[], byte[]> keyValue = pendingIterator.next();
+
+ K key = decodeKey(keyValue.getKey());
+ V value = decodeValue(keyValue.getValue());
+
+ providedKeys.add(keyValue.getKey());
+ return new AbstractMap.SimpleEntry(key, value);
+ }
+
+ @Override
+ public void remove() {
+ throw new UnsupportedOperationException();
+ }
+
+ /**
+ * Load some part of state KVs from storage and returns iterator of
cached data from storage.
+ *
+ * @return Iterator of loaded state KVs
+ */
+ protected abstract Iterator<Map.Entry<byte[],byte[]>>
loadChunkFromStateStorage();
--- End diff --
Here it assumes the state implementations store in binary format? Can't it
return `Iterator<Map.Entry<K, V>>` instead and not assume any specific
implementation and let sub-classes do the decoding ?
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