Fix failing tests and update per comments

Author: atris

modules/ingest-common/src/main/java/org/opensearch/ingest/common/HierarchicalRoutingProcessor.java

@@ -34,13 +34,13 @@
 public final class HierarchicalRoutingProcessor extends AbstractProcessor {
 
     public static final String TYPE = "hierarchical_routing";
-    private static final String VERSION = "3.2.0";
 
     private final String pathField;
     private final int anchorDepth;
     private final String pathSeparator;
     private final boolean ignoreMissing;
     private final boolean overrideExisting;
+    private final java.util.regex.Pattern pathSeparatorPattern;
 
     HierarchicalRoutingProcessor(
         String tag,
@@ -57,6 +57,7 @@ public final class HierarchicalRoutingProcessor extends AbstractProcessor {
         this.pathSeparator = pathSeparator;
         this.ignoreMissing = ignoreMissing;
         this.overrideExisting = overrideExisting;
+        this.pathSeparatorPattern = java.util.regex.Pattern.compile(java.util.regex.Pattern.quote(pathSeparator));
     }
 
     @Override
@@ -75,11 +76,8 @@ public IngestDocument execute(IngestDocument document) throws Exception {
 
         Object pathValue = document.getFieldValue(pathField, Object.class, ignoreMissing);
 
-        if (pathValue == null) {
-            if (ignoreMissing) {
-                return document;
-            }
-            throw new IllegalArgumentException("field [" + pathField + "] doesn't exist");
+        if (pathValue == null && ignoreMissing) {
+            return document;
         }
 
         String path = pathValue.toString();
@@ -102,7 +100,7 @@ public IngestDocument execute(IngestDocument document) throws Exception {
      */
     private String computeRoutingValue(String path) {
         String normalizedPath = normalizePath(path);
-        String[] segments = normalizedPath.split(java.util.regex.Pattern.quote(pathSeparator));
+        String[] segments = pathSeparatorPattern.split(normalizedPath);
         String anchor = extractAnchor(segments, anchorDepth);
 
         // Use MurmurHash3 for consistent, fast hashing

modules/ingest-common/src/test/java/org/opensearch/ingest/common/IngestCommonModulePluginTests.java

@@ -73,7 +73,8 @@ public void testAllowlistNotSpecified() throws IOException {
                 "script",
                 "dissect",
                 "uppercase",
-                "split"
+                "split",
+                "hierarchical_routing"
             );
             assertEquals(expected, plugin.getProcessors(createParameters(settings)).keySet());
         }

modules/search-pipeline-common/src/main/java/org/opensearch/search/pipeline/common/HierarchicalRoutingSearchProcessor.java

@@ -23,9 +23,7 @@
 import org.opensearch.search.pipeline.SearchRequestProcessor;
 
 import java.nio.charset.StandardCharsets;
-import java.util.ArrayList;
 import java.util.HashSet;
-import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
@@ -50,6 +48,7 @@ public class HierarchicalRoutingSearchProcessor extends AbstractProcessor implem
     private final int anchorDepth;
     private final String pathSeparator;
     private final boolean enableAutoDetection;
+    private final java.util.regex.Pattern pathSeparatorPattern;
 
     HierarchicalRoutingSearchProcessor(
         String tag,
@@ -65,6 +64,7 @@ public class HierarchicalRoutingSearchProcessor extends AbstractProcessor implem
         this.anchorDepth = anchorDepth;
         this.pathSeparator = pathSeparator;
         this.enableAutoDetection = enableAutoDetection;
+        this.pathSeparatorPattern = java.util.regex.Pattern.compile(java.util.regex.Pattern.quote(pathSeparator));
     }
 
     @Override
@@ -88,7 +88,7 @@ public SearchRequest processRequest(SearchRequest request) throws Exception {
 
         // If we found path information, compute routing and apply it
         if (!routingValues.isEmpty()) {
-            List<String> computedRouting = new ArrayList<>();
+            Set<String> computedRouting = new HashSet<>();
             for (String path : routingValues) {
                 String routingValue = computeRoutingValue(path);
                 if (routingValue != null) {
@@ -199,7 +199,7 @@ private String computeRoutingValue(String path) {
         }
 
         String normalizedPath = normalizePath(path);
-        String[] segments = normalizedPath.split(java.util.regex.Pattern.quote(pathSeparator));
+        String[] segments = pathSeparatorPattern.split(normalizedPath);
         String anchor = extractAnchor(segments, anchorDepth);
 
         // Use MurmurHash3 for consistent, fast hashing (same as ingest processor)

modules/search-pipeline-common/src/test/java/org/opensearch/search/pipeline/common/SearchPipelineCommonModulePluginTests.java

@@ -81,7 +81,10 @@ private void runAllowlistTest(
     public void testAllowlistNotSpecified() throws IOException {
         final Settings settings = Settings.EMPTY;
         try (SearchPipelineCommonModulePlugin plugin = new SearchPipelineCommonModulePlugin()) {
-            assertEquals(Set.of("oversample", "filter_query", "script"), plugin.getRequestProcessors(createParameters(settings)).keySet());
+            assertEquals(
+                Set.of("oversample", "filter_query", "script", "hierarchical_routing_search"),
+                plugin.getRequestProcessors(createParameters(settings)).keySet()
+            );
             assertEquals(
                 Set.of("rename_field", "truncate_hits", "collapse", "split", "sort"),
                 plugin.getResponseProcessors(createParameters(settings)).keySet()