[GitHub] [kafka] mjsax commented on a diff in pull request #13264: KAFKA-14491: [12/N] Relax requirement that KTable stores must be TimestampedKVStores

["mjsax (via GitHub)" <gi...@apache.org>]

mjsax commented on code in PR #13264:
URL: https://github.com/apache/kafka/pull/13264#discussion_r1122525554


##########
streams/src/main/java/org/apache/kafka/streams/state/internals/KeyValueStoreWrapper.java:
##########
@@ -0,0 +1,204 @@
+/*
+ * 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.kafka.streams.state.internals;
+
+import org.apache.kafka.streams.errors.InvalidStateStoreException;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.api.ProcessorContext;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.query.PositionBound;
+import org.apache.kafka.streams.query.Query;
+import org.apache.kafka.streams.query.QueryConfig;
+import org.apache.kafka.streams.query.QueryResult;
+import org.apache.kafka.streams.state.TimestampedKeyValueStore;
+import org.apache.kafka.streams.state.ValueAndTimestamp;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+
+/**
+ * A wrapper class for non-windowed key-value stores used within the DSL. All such stores are
+ * instances of either {@link TimestampedKeyValueStore} or {@link VersionedKeyValueStore}.
+ *
+ * @param <K> The key type
+ * @param <V> The value type
+ */
+public class KeyValueStoreWrapper<K, V> implements StateStore {
+
+    private TimestampedKeyValueStore<K, V> timestampedStore = null;
+    private VersionedKeyValueStore<K, V> versionedStore = null;
+
+    public KeyValueStoreWrapper(final ProcessorContext<?, ?> context, final String storeName) {
+        try {
+            // first try timestamped store
+            timestampedStore = context.getStateStore(storeName);
+            return;
+        } catch (final ClassCastException e) {
+            // ignore since could be versioned store instead
+        }
+
+        try {
+            // next try versioned store
+            versionedStore = context.getStateStore(storeName);
+        } catch (final ClassCastException e) {
+            throw new InvalidStateStoreException("KTable source state store must implement either TimestampedKeyValueStore or VersionedKeyValueStore.");
+        }
+    }
+
+    public ValueAndTimestamp<V> get(final K key) {
+        if (timestampedStore != null) {
+            return timestampedStore.get(key);
+        }
+        if (versionedStore != null) {
+            final VersionedRecord<V> versionedRecord = versionedStore.get(key);
+            return versionedRecord == null
+                ? null
+                : ValueAndTimestamp.make(versionedRecord.value(), versionedRecord.timestamp());
+        }
+        throw new IllegalStateException("KeyValueStoreWrapper must be initialized with either timestamped or versioned store");
+    }
+
+    public void put(final K key, final V value, final long timestamp) {
+        if (timestampedStore != null) {
+            timestampedStore.put(key, ValueAndTimestamp.make(value, timestamp));
+            return;
+        }
+        if (versionedStore != null) {
+            versionedStore.put(key, value, timestamp);
+            return;
+        }
+        throw new IllegalStateException("KeyValueStoreWrapper must be initialized with either timestamped or versioned store");
+    }
+
+    public StateStore getStore() {

Review Comment:
   My proposal was actually to have three member, the previously existing `KeyValueStore keyValueStore`, `VersionedStore versionStore` and a new `Store store`. So we just simplify the code for the case when we don't care about the store type, but when we care we check if `keyValueStore != null` or `versionStore != null` and do the right thing.
   
   Sorry for not explaining it good enough -- using an enum works, too, I guess, but also tend to agree it a little overkill. But you made the change already... So maybe also not worth to revert it again to sue `KeyValueStore keyValueStore` and `VersionedStore versionStore` as you did originally.



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