Don't cache search queries where the cache hit chance is low. (#8659)

Author: isoos

CHANGELOG.md

@@ -2,6 +2,7 @@ Important changes to data models, configuration, and migrations between each
 AppEngine version, listed here to ease deployment and troubleshooting.
 
 ## Next Release (replace with git tag when deployed)
+ * Note: search queries with multiple components are not cached.
 
 ## `20250320t094500-all`
  * Bump runtimeVersion to `2025.03.18`.

app/lib/package/search_adapter.dart

@@ -35,8 +35,10 @@ class SearchAdapter {
   ///
   /// When the `search` service fails, it falls back to use the name tracker to
   /// provide package names and perform search in that set.
-  Future<SearchResultPage> search(SearchForm form,
-      {required String? rateLimitKey}) async {
+  Future<SearchResultPage> search(
+    SearchForm form, {
+    required String? rateLimitKey,
+  }) async {
     final result = (await _searchOrFallback(form, rateLimitKey, true))!;
     final views = await _getPackageViewsFromHits([...result.packageHits]);
     return SearchResultPage(

app/lib/search/search_client.dart

@@ -60,6 +60,15 @@ class SearchClient {
 
     final serviceUrlParams = Uri(queryParameters: query.toUriQueryParameters());
 
+    // Don't use cache in cases where there is a high chance of cache miss.
+    // This is a rough heuristic, counting the distinct components in the
+    // user-provided query. Such components are:
+    // - free form text (counts as 1 regardless of word count)
+    // - `sdk:...`, `platform:...` and other tags (counts as 1 each)
+    if (query.parsedQuery.componentCount > 2) {
+      skipCache = true;
+    }
+
     // returns null on timeout (after 5 seconds)
     Future<http.Response?> doCallHttpServiceEndpoint({String? prefix}) async {
       final httpHostPort = prefix ?? activeConfiguration.searchServicePrefix;

pkg/_pub_shared/lib/search/search_form.dart

@@ -324,6 +324,13 @@ class ParsedQueryText {
       !hasAnyDependency &&
       tagsPredicate.isEmpty;
 
+  int get componentCount =>
+      (text == null || text!.isEmpty ? 0 : 1) +
+      (packagePrefix == null ? 0 : 1) +
+      refDependencies.length +
+      allDependencies.length +
+      tagsPredicate._values.length;
+
   @override
   String toString() {
     if (hasOnlyFreeText) return text!;