Fix exceptions in index pattern conflict checks (#134231) (#134291)

We already fixed an issue with this in #128362 but apparently another
instance of the unnecessary determinization was hiding elsewhere and in
its current state throws exceptions starting with Lucene 10 on complext
patterns.
This change adds the same fix as #128362 and adds a test that would have
triggered this.

Closes #133652

Author: cbuescher

docs/changelog/134231.yaml

@@ -0,0 +1,6 @@
+pr: 134231
+summary: Fix unnecessary determinization in index pattern conflict checks
+area: Indices APIs
+type: bug
+issues:
+ - 133652

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateService.java

@@ -995,12 +995,16 @@ static Map<String, List<String>> findConflictingV2Templates(
         boolean checkPriority,
         long priority
     ) {
-        Automaton v1automaton = Regex.simpleMatchToAutomaton(indexPatterns.toArray(Strings.EMPTY_ARRAY));
+        // No need to determinize the automaton, as it is only used to check for intersection with another automaton.
+        // Determinization is avoided because it can fail or become very costly due to state explosion.
+        Automaton v1automaton = Regex.simpleMatchToNonDeterminizedAutomaton(indexPatterns.toArray(Strings.EMPTY_ARRAY));
         Map<String, List<String>> overlappingTemplates = new TreeMap<>();
         for (Map.Entry<String, ComposableIndexTemplate> entry : project.templatesV2().entrySet()) {
             String name = entry.getKey();
             ComposableIndexTemplate template = entry.getValue();
-            Automaton v2automaton = Regex.simpleMatchToAutomaton(template.indexPatterns().toArray(Strings.EMPTY_ARRAY));
+            // No need to determinize the automaton, as it is only used to check for intersection with another automaton.
+            // Determinization is avoided because it can fail or become very costly due to state explosion.
+            Automaton v2automaton = Regex.simpleMatchToNonDeterminizedAutomaton(template.indexPatterns().toArray(Strings.EMPTY_ARRAY));
             if (Operations.isEmpty(Operations.intersection(v1automaton, v2automaton)) == false) {
                 if (checkPriority == false || priority == template.priorityOrZero()) {
                     logger.debug(

server/src/test/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateServiceTests.java

@@ -2495,6 +2495,23 @@ public void testV2TemplateOverlaps() throws Exception {
         }
     }
 
+    /**
+     * test that using complex index patterns doesn't run into a too_complex_to_determinize_exception,
+     * see https://github.com/elastic/elasticsearch/issues/133652
+     */
+    public void testFindConflictingTemplates_complex_pattern() throws Exception {
+        ProjectMetadata initialProject = ProjectMetadata.builder(randomProjectIdOrDefault()).build();
+        List<String> complexPattern = new ArrayList<>();
+        for (int i = 1; i < 20; i++) {
+            complexPattern.add("cluster-somenamespace-*-app" + i + "*");
+        }
+        ComposableIndexTemplate template = ComposableIndexTemplate.builder().indexPatterns(complexPattern).build();
+        MetadataIndexTemplateService service = getMetadataIndexTemplateService();
+        ProjectMetadata project = service.addIndexTemplateV2(initialProject, false, "foo", template);
+        assertEquals(0, MetadataIndexTemplateService.findConflictingV1Templates(project, "foo", complexPattern).size());
+        assertEquals(0, MetadataIndexTemplateService.findConflictingV2Templates(project, "foo", complexPattern).size());
+    }
+
     /**
      * Tests to add two component templates but ignores both with is valid
      *