refactor: split distributed package into merge and worker sub-packages

distributed/ (4 orchestration files):
  DistributedScanExecutor, QueryAnalyzer, FilePartitioner, NodeDiscovery

distributed/merge/ (5 files):
  ResultMerger, AggregationReducer, TopKMerger, ResultSerializer, MergeStrategy

distributed/worker/ (6 files):
  WorkerQueryExecutor, WorkerCredentialResolver, WorkerQueryTransportAction,
  WorkerQueryAction, WorkerQueryRequest, WorkerQueryResponse

Author: vamsimanohar

sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/LakehousePlugin.java

@@ -21,8 +21,8 @@
 import org.opensearch.lakehouse.action.LakehousePplRestAction;
 import org.opensearch.lakehouse.action.LakehouseSqlRestAction;
 import org.opensearch.lakehouse.distributed.NodeDiscovery;
-import org.opensearch.lakehouse.distributed.WorkerQueryAction;
-import org.opensearch.lakehouse.distributed.WorkerQueryTransportAction;
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryAction;
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryTransportAction;
 import org.opensearch.lakehouse.schema.IcebergSchemaContributor;
 import org.opensearch.action.ActionRequest;
 import org.opensearch.core.action.ActionResponse;

sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/DistributedScanExecutor.java

@@ -18,6 +18,13 @@
 import org.opensearch.core.action.ActionListener;
 import org.opensearch.core.common.io.stream.StreamInput;
 import org.opensearch.lakehouse.LakehousePlugin;
+import org.opensearch.lakehouse.distributed.merge.MergeStrategy;
+import org.opensearch.lakehouse.distributed.merge.ResultMerger;
+import org.opensearch.lakehouse.distributed.merge.ResultSerializer;
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryAction;
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryExecutor;
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryRequest;
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryResponse;
 import org.opensearch.threadpool.ThreadPool;
 import org.opensearch.transport.TransportException;
 import org.opensearch.transport.TransportResponseHandler;

sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/QueryAnalyzer.java

@@ -16,6 +16,7 @@
 import org.apache.calcite.rel.core.Sort;
 import org.apache.calcite.rex.RexLiteral;
 import org.apache.calcite.sql.SqlKind;
+import org.opensearch.lakehouse.distributed.merge.MergeStrategy;
 
 import java.util.List;
 

…ouse/distributed/AggregationReducer.java …istributed/merge/AggregationReducer.javasandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/AggregationReducer.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/AggregationReducer.java sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/AggregationReducer.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/AggregationReducer.java

@@ -6,7 +6,9 @@
  * compatible open source license.
  */
 
-package org.opensearch.lakehouse.distributed;
+package org.opensearch.lakehouse.distributed.merge;
+
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryResponse;
 
 import java.util.List;
 

…lakehouse/distributed/MergeStrategy.java …use/distributed/merge/MergeStrategy.javasandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/MergeStrategy.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/MergeStrategy.java sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/MergeStrategy.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/MergeStrategy.java

@@ -6,7 +6,7 @@
  * compatible open source license.
  */
 
-package org.opensearch.lakehouse.distributed;
+package org.opensearch.lakehouse.distributed.merge;
 
 /**
  * Merge strategy for combining partial results from distributed worker nodes.

…/lakehouse/distributed/ResultMerger.java …ouse/distributed/merge/ResultMerger.javasandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/ResultMerger.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/ResultMerger.java sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/ResultMerger.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/ResultMerger.java

@@ -6,9 +6,10 @@
  * compatible open source license.
  */
 
-package org.opensearch.lakehouse.distributed;
+package org.opensearch.lakehouse.distributed.merge;
 
 import org.apache.calcite.sql.SqlKind;
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryResponse;
 
 import java.util.ArrayList;
 import java.util.Collections;

…ehouse/distributed/ResultSerializer.java …/distributed/merge/ResultSerializer.javasandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/ResultSerializer.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/ResultSerializer.java sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/ResultSerializer.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/ResultSerializer.java

@@ -6,7 +6,9 @@
  * compatible open source license.
  */
 
-package org.opensearch.lakehouse.distributed;
+package org.opensearch.lakehouse.distributed.merge;
+
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryResponse;
 
 import java.util.ArrayList;
 import java.util.List;

…ch/lakehouse/distributed/TopKMerger.java …ehouse/distributed/merge/TopKMerger.javasandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/TopKMerger.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/TopKMerger.java sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/TopKMerger.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/TopKMerger.java

@@ -6,7 +6,9 @@
  * compatible open source license.
  */
 
-package org.opensearch.lakehouse.distributed;
+package org.opensearch.lakehouse.distributed.merge;
+
+import org.opensearch.lakehouse.distributed.worker.WorkerQueryResponse;
 
 import java.util.ArrayList;
 import java.util.Comparator;

sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/merge/package-info.java

@@ -0,0 +1,15 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+/**
+ * Result merging strategies for distributed query execution.
+ * <p>
+ * Contains the merge dispatcher, aggregation reducer, top-K merger,
+ * result serializer, and merge strategy enum.
+ */
+package org.opensearch.lakehouse.distributed.merge;

…istributed/WorkerCredentialResolver.java …ted/worker/WorkerCredentialResolver.javasandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/WorkerCredentialResolver.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/worker/WorkerCredentialResolver.java sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/WorkerCredentialResolver.java renamed to sandbox/plugins/lakehouse-iceberg/src/main/java/org/opensearch/lakehouse/distributed/worker/WorkerCredentialResolver.java

@@ -6,7 +6,7 @@
  * compatible open source license.
  */
 
-package org.opensearch.lakehouse.distributed;
+package org.opensearch.lakehouse.distributed.worker;
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;