Bug 707946 - Improve performances of hasChildren for tag queries.

r=dietrich sr=gavin

toolkit/components/build/nsToolkitCompsCID.h

@@ -110,6 +110,9 @@
 #define NS_LIVEMARKSERVICE_CONTRACTID \
   "@mozilla.org/browser/livemark-service;2"
 
+#define NS_TAGGINGSERVICE_CONTRACTID \
+"@mozilla.org/browser/tagging-service;1"
+
 #define NS_FAVICONSERVICE_CONTRACTID \
   "@mozilla.org/browser/favicon-service;1"
 

toolkit/components/places/nsITaggingService.idl

@@ -41,7 +41,7 @@
 interface nsIURI;
 interface nsIVariant;
 
-[scriptable, uuid(e39cea60-7e6d-4c8b-80a3-997af1c2cbcb)]
+[scriptable, uuid(f816b4df-f733-4dbd-964d-8bfc92a475b2)]
 interface nsITaggingService : nsISupports
 {
   /**
@@ -95,6 +95,13 @@ interface nsITaggingService : nsISupports
    * Retrieves all tags used to tag URIs in the data-base (sorted by name).
    */
   readonly attribute nsIVariant allTags;
+
+  /**
+   * Whether any tags exist.
+   *
+   * @note This is faster than allTags.length, since doesn't need to sort tags.
+   */
+  readonly attribute boolean hasTags;
 };
 
 %{C++

toolkit/components/places/nsNavHistoryResult.cpp

@@ -2247,31 +2247,28 @@ nsNavHistoryQueryResultNode::OpenContainer()
 NS_IMETHODIMP
 nsNavHistoryQueryResultNode::GetHasChildren(bool* aHasChildren)
 {
+  *aHasChildren = false;
+
   if (!CanExpand()) {
-    *aHasChildren = false;
     return NS_OK;
   }
 
   PRUint16 resultType = mOptions->ResultType();
+
+  // Tags are always populated, otherwise they are removed.
+  if (resultType == nsINavHistoryQueryOptions::RESULTS_AS_TAG_CONTENTS) {
+    *aHasChildren = true;
+    return NS_OK;
+  }
+
   // For tag containers query we must check if we have any tag
   if (resultType == nsINavHistoryQueryOptions::RESULTS_AS_TAG_QUERY) {
-    nsRefPtr<Database> DB = Database::GetDatabase();
-    NS_ENSURE_STATE(DB);
-    nsCOMPtr<mozIStorageStatement> stmt = DB->GetStatement(
-      "SELECT id FROM moz_bookmarks WHERE parent = :tags_folder LIMIT 1"
-    );
-    NS_ENSURE_STATE(stmt);
-    mozStorageStatementScoper scoper(stmt);
-
-    nsNavHistory* history = nsNavHistory::GetHistoryService();
-    NS_ENSURE_STATE(history);
-    nsresult rv = stmt->BindInt64ByName(NS_LITERAL_CSTRING("tags_folder"),
-                                        history->GetTagsFolder());
-    NS_ENSURE_SUCCESS(rv, rv);
-
-    rv = stmt->ExecuteStep(aHasChildren);
-    NS_ENSURE_SUCCESS(rv, rv);
-
+    nsCOMPtr<nsITaggingService> tagging =
+      do_GetService(NS_TAGGINGSERVICE_CONTRACTID);
+    if (tagging) {
+      bool hasTags;
+      *aHasChildren = NS_SUCCEEDED(tagging->GetHasTags(&hasTags)) && hasTags;
+    }
     return NS_OK;
   }
 

toolkit/components/places/nsTaggingService.js

@@ -350,6 +350,11 @@ TaggingService.prototype = {
     return allTags;
   },
 
+  // nsITaggingService
+  get hasTags() {
+    return this._tagFolders.length > 0;
+  },
+
   // nsIObserver
   observe: function TS_observe(aSubject, aTopic, aData) {
     if (aTopic == TOPIC_SHUTDOWN) {