addressing nits

Signed-off-by: Sarthak Aggarwal <[email protected]>

server/src/main/java/org/opensearch/index/compositeindex/datacube/startree/builder/BaseStarTreeBuilder.java

@@ -557,7 +557,7 @@ void build(Iterator<StarTreeDocument> starTreeDocumentIterator) throws IOExcepti
         int numAggregatedStarTreeDocument = numStarTreeDocs - numStarTreeDocument - numStarTreeDocumentUnderStarNode;
         logger.debug("Finished creating aggregated documents : {}", numAggregatedStarTreeDocument);
 
-        // TODO: When StarTree Codec is ready
+        // TODO: When StarTreeFactory Codec is ready
         // Create doc values indices in disk
         // Serialize and save in disk
         // Write star tree metadata for off heap implementation

server/src/main/java/org/opensearch/index/compositeindex/datacube/startree/builder/StarTreeBuilder.java

@@ -34,7 +34,7 @@ public interface StarTreeBuilder extends Closeable {
     void build(Map<String, DocValuesProducer> fieldProducerMap) throws IOException;
 
     /**
-     * Builds the star tree using StarTree values from multiple segments
+     * Builds the star tree using StarTreeFactory values from multiple segments
      *
      * @param starTreeValuesSubs           contains the star tree values from multiple segments
      * @throws IOException when we are unable to build star-tree

server/src/main/java/org/opensearch/index/compositeindex/datacube/startree/fileformats/meta/StarTreeMetaWriter.java

@@ -58,6 +58,8 @@ public static void writeStarTreeMetadata(
         long initialMetaFilePointer = metaOut.getFilePointer();
 
         writeMetaHeader(metaOut);
+
+        // TODO: Replace the parameters with StarTreeMetadata class object
         writeMeta(metaOut, metricAggregatorInfos, starTreeField, numNodes, segmentAggregatedCount, dataFilePointer, dataFileLength);
 
         logger.debug(

server/src/main/java/org/opensearch/index/compositeindex/datacube/startree/node/StarTreeFactory.java

@@ -0,0 +1,42 @@
+/*
+ * 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.
+ */
+package org.opensearch.index.compositeindex.datacube.startree.node;
+
+import org.apache.lucene.store.IndexInput;
+import org.apache.lucene.store.RandomAccessInput;
+import org.opensearch.index.compositeindex.datacube.startree.fileformats.meta.StarTreeMetadata;
+import org.opensearch.index.compositeindex.datacube.startree.fileformats.node.FixedLengthStarTreeNode;
+
+import java.io.IOException;
+
+/**
+ * A factory class for creating off-heap implementations of star-tree nodes.
+ *
+ * <p>This class provides a static factory method to create instances of {@link StarTreeNode}
+ * from an {@link IndexInput} and {@link StarTreeMetadata}. The implementation uses an
+ * off-heap data structure to store and access the star-tree data efficiently using random access.
+ *
+ * @opensearch.experimental
+ */
+public class StarTreeFactory {
+
+    /**
+     * Creates a new instance of {@link StarTreeNode} from the provided {@link IndexInput} and
+     * {@link StarTreeMetadata}.
+     *
+     * @param data The {@link IndexInput} containing the star-tree data.
+     * @param starTreeMetadata The {@link StarTreeMetadata} containing metadata about the star-tree.
+     * @return A new instance of {@link StarTreeNode} representing the root of the star-tree.
+     * @throws IOException If an error occurs while reading the star-tree data.
+     */
+    public static StarTreeNode createStarTree(IndexInput data, StarTreeMetadata starTreeMetadata) throws IOException {
+        RandomAccessInput in = data.randomAccessSlice(0, starTreeMetadata.getDataLength());
+        return new FixedLengthStarTreeNode(in, 0);
+    }
+
+}

server/src/main/java/org/opensearch/index/compositeindex/datacube/startree/node/StarTreeNodeType.java

@@ -9,7 +9,7 @@
 package org.opensearch.index.compositeindex.datacube.startree.node;
 
 /**
- * Represents the different types of nodes in a StarTree data structure.
+ * Represents the different types of nodes in a StarTreeFactory data structure.
  *
  * <p>
  * In order to handle different node types, we use a byte value to represent the node type.

server/src/test/java/org/opensearch/index/compositeindex/datacube/startree/fileformats/data/StarTreeFileFormatsTests.java

@@ -15,7 +15,7 @@
 import org.opensearch.index.compositeindex.datacube.startree.fileformats.StarTreeWriter;
 import org.opensearch.index.compositeindex.datacube.startree.fileformats.meta.StarTreeMetadata;
 import org.opensearch.index.compositeindex.datacube.startree.node.InMemoryTreeNode;
-import org.opensearch.index.compositeindex.datacube.startree.node.StarTree;
+import org.opensearch.index.compositeindex.datacube.startree.node.StarTreeFactory;
 import org.opensearch.index.compositeindex.datacube.startree.node.StarTreeNode;
 import org.opensearch.index.compositeindex.datacube.startree.node.StarTreeNodeType;
 import org.opensearch.test.OpenSearchTestCase;
@@ -64,9 +64,8 @@ public void test_StarTreeNode() throws IOException {
         StarTreeMetadata starTreeMetadata = mock(StarTreeMetadata.class);
         when(starTreeMetadata.getDataLength()).thenReturn(starTreeDataLength);
         when(starTreeMetadata.getDataStartFilePointer()).thenReturn(0L);
-        StarTree starTree = new StarTree(dataIn, starTreeMetadata);
 
-        StarTreeNode starTreeNode = starTree.getRoot();
+        StarTreeNode starTreeNode = StarTreeFactory.createStarTree(dataIn, starTreeMetadata);
         Queue<StarTreeNode> queue = new ArrayDeque<>();
         queue.add(starTreeNode);
 
@@ -116,9 +115,8 @@ public void test_starTreeSearch() throws IOException {
         StarTreeMetadata starTreeMetadata = mock(StarTreeMetadata.class);
         when(starTreeMetadata.getDataLength()).thenReturn(starTreeDataLength);
         when(starTreeMetadata.getDataStartFilePointer()).thenReturn(0L);
-        StarTree starTree = new StarTree(dataIn, starTreeMetadata);
 
-        StarTreeNode starTreeNode = starTree.getRoot();
+        StarTreeNode starTreeNode = StarTreeFactory.createStarTree(dataIn, starTreeMetadata);
         InMemoryTreeNode inMemoryTreeNode = inMemoryTreeNodeMap.get(starTreeNode.getDimensionValue());
         assertNotNull(inMemoryTreeNode);
 

server/src/test/java/org/opensearch/index/compositeindex/datacube/startree/fileformats/node/FixedLengthStarTreeNodeTests.java

@@ -15,7 +15,7 @@
 import org.opensearch.index.compositeindex.datacube.startree.fileformats.StarTreeWriter;
 import org.opensearch.index.compositeindex.datacube.startree.fileformats.meta.StarTreeMetadata;
 import org.opensearch.index.compositeindex.datacube.startree.node.InMemoryTreeNode;
-import org.opensearch.index.compositeindex.datacube.startree.node.StarTree;
+import org.opensearch.index.compositeindex.datacube.startree.node.StarTreeFactory;
 import org.opensearch.index.compositeindex.datacube.startree.utils.StarTreeUtils;
 import org.opensearch.test.OpenSearchTestCase;
 import org.junit.Before;
@@ -98,9 +98,8 @@ public void setup() throws IOException {
         StarTreeMetadata starTreeMetadata = mock(StarTreeMetadata.class);
         when(starTreeMetadata.getDataLength()).thenReturn(starTreeDataLength);
         when(starTreeMetadata.getDataStartFilePointer()).thenReturn(0L);
-        StarTree starTree = new StarTree(dataIn, starTreeMetadata);
 
-        starTreeNode = (FixedLengthStarTreeNode) starTree.getRoot();
+        starTreeNode = (FixedLengthStarTreeNode) StarTreeFactory.createStarTree(dataIn, starTreeMetadata);
 
     }