bad assert and hardcoding to 8 for target size for now for parent centroid clustering

Author: john-wagster

server/src/main/java/org/elasticsearch/index/codec/vectors/DefaultIVFVectorsWriter.java

@@ -381,7 +381,7 @@ public DocIndexIterator iterator() {
 
         HierarchicalKMeans hierarchicalKMeans = new HierarchicalKMeans(fieldInfo.getVectorDimension());
         // TODO: evaluate further whether 512 is better than other sizes like 32 or sqrt(centroids.length)
-        return hierarchicalKMeans.cluster(centroidsAsFVV, 512); // centroids.length / (int) Math.sqrt(centroids.length));
+        return hierarchicalKMeans.cluster(centroidsAsFVV, 8); // centroids.length / (int) Math.sqrt(centroids.length));
     }
 
     static int[][] buildCentroidAssignments(int centroidCount, int[] assignments, int[] soarAssignments) {

server/src/main/java/org/elasticsearch/index/codec/vectors/IVFVectorsWriter.java

@@ -317,7 +317,6 @@ private void mergeOneFieldIVF(FieldInfo fieldInfo, MergeState mergeState) throws
                 numCentroids = centroidAssignments.numCentroids();
                 numClusters = centroidAssignments.centroids().length;
                 assignmentsByCluster = centroidAssignments.assignmentsByCluster();
-                assert centroidAssignments.clusterToCentroidMap() != null;
                 clusterToCentroidMap = centroidAssignments.clusterToCentroidMap();
                 success = true;
             } finally {