vvcephei commented on a change in pull request #11582:
URL: https://github.com/apache/kafka/pull/11582#discussion_r771515988
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File path:
streams/src/main/java/org/apache/kafka/streams/state/internals/StoreQueryUtils.java
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@@ -16,18 +16,78 @@
*/
package org.apache.kafka.streams.state.internals;
+import org.apache.kafka.common.utils.Bytes;
import org.apache.kafka.streams.processor.StateStore;
import org.apache.kafka.streams.processor.StateStoreContext;
import org.apache.kafka.streams.processor.api.RecordMetadata;
+import org.apache.kafka.streams.query.FailureReason;
+import org.apache.kafka.streams.query.KeyQuery;
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.QueryResult;
+import org.apache.kafka.streams.state.KeyValueStore;
+import java.io.PrintWriter;
+import java.io.StringWriter;
import java.util.Map;
+import static org.apache.kafka.common.utils.Utils.mkEntry;
+import static org.apache.kafka.common.utils.Utils.mkMap;
+
public final class StoreQueryUtils {
+ /**
+ * a utility interface to facilitate stores' query dispatch logic,
+ * allowing them to generically store query execution logic as the values
+ * in a map.
+ */
+ @FunctionalInterface
+ public interface QueryHandler {
+ QueryResult<?> apply(
+ final Query<?> query,
+ final PositionBound positionBound,
+ final boolean collectExecutionInfo,
+ final StateStore store
+ );
+ }
+
+
+ @SuppressWarnings("unchecked")
+ private static final Map<Class<?>, QueryHandler> QUERY_HANDLER_MAP =
Review comment:
They both exist to dispatch query execution logic. The MeteredStores'
logic is to translate results from the inner stores, and the inner stores'
logic is to execute the query. Since we have a lot of functionally identical
stores (i.e., many KeyValue stores, etc.), it made sense to consolidate their
execution logic here instead of duplicating it in every store class.
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