Bug 599978 - Part 2: Asynchronous isVisited checks should use a read-only cloned connection

Changes to create and use the read-only cloned connection.
r=mak

toolkit/components/places/src/History.cpp

@@ -170,7 +170,7 @@ public:
   // If we are a content process, always remote the request to the
   // parent process.
   if (XRE_GetProcessType() == GeckoProcessType_Content) {
-    mozilla::dom::ContentChild * cpc = 
+    mozilla::dom::ContentChild* cpc =
       mozilla::dom::ContentChild::GetSingleton();
     NS_ASSERTION(cpc, "Content Protocol is NULL!");
     (void)cpc->SendStartVisitedQuery(aURI);
@@ -178,9 +178,8 @@ public:
   }
 #endif
 
-    nsNavHistory* navHist = nsNavHistory::GetHistoryService();
-    NS_ENSURE_TRUE(navHist, NS_ERROR_FAILURE);
-    mozIStorageStatement* stmt = navHist->GetStatementById(DB_IS_PAGE_VISITED);
+    mozIStorageAsyncStatement* stmt =
+      History::GetService()->GetIsVisitedStatement();
     NS_ENSURE_STATE(stmt);
 
     // Bind by index for performance.
@@ -260,7 +259,7 @@ class FailSafeFinishTask
 {
 public:
   FailSafeFinishTask()
-  : mAppended(false) 
+  : mAppended(false)
   {
   }
 
@@ -952,6 +951,37 @@ History::NotifyVisited(nsIURI* aURI)
   mObservers.RemoveEntry(aURI);
 }
 
+mozIStorageAsyncStatement*
+History::GetIsVisitedStatement()
+{
+  if (mIsVisitedStatement) {
+    return mIsVisitedStatement;
+  }
+
+  // If we don't yet have a database connection, go ahead and clone it now.
+  if (!mReadOnlyDBConn) {
+    nsNavHistory* history = nsNavHistory::GetHistoryService();
+    NS_ENSURE_TRUE(history, nsnull);
+
+    nsCOMPtr<mozIStorageConnection> dbConn;
+    (void)history->GetDBConnection(getter_AddRefs(dbConn));
+    NS_ENSURE_TRUE(dbConn, nsnull);
+
+    (void)dbConn->Clone(PR_TRUE, getter_AddRefs(mReadOnlyDBConn));
+    NS_ENSURE_TRUE(mReadOnlyDBConn, nsnull);
+  }
+
+  // Now we can create our cached statement.
+  nsresult rv = mReadOnlyDBConn->CreateAsyncStatement(NS_LITERAL_CSTRING(
+    "SELECT h.id "
+    "FROM moz_places h "
+    "WHERE url = ?1 "
+      "AND EXISTS(SELECT id FROM moz_historyvisits WHERE place_id = h.id LIMIT 1) "
+  ),  getter_AddRefs(mIsVisitedStatement));
+  NS_ENSURE_SUCCESS(rv, nsnull);
+  return mIsVisitedStatement;
+}
+
 /* static */
 History*
 History::GetService()
@@ -1006,6 +1036,10 @@ History::Shutdown()
     nsCOMPtr<Step> deadTaskWalking =
       dont_AddRef(static_cast<Step*>(mPendingVisits.PopFront()));
   }
+
+  if (mReadOnlyDBConn) {
+    (void)mReadOnlyDBConn->AsyncClose(nsnull);
+  }
 }
 
 ////////////////////////////////////////////////////////////////////////////////

toolkit/components/places/src/History.h

@@ -48,6 +48,7 @@
 #include "nsTArray.h"
 #include "nsDeque.h"
 #include "nsIObserver.h"
+#include "mozIStorageConnection.h"
 
 namespace mozilla {
 namespace places {
@@ -71,7 +72,7 @@ public:
    * @param aURI
    *        The URI to notify about.
    */
-  void NotifyVisited(nsIURI *aURI);
+  void NotifyVisited(nsIURI* aURI);
 
   /**
    * Append a task to the queue for SQL queries that need to happen
@@ -93,19 +94,38 @@ public:
    */
   void CurrentTaskFinished();
 
+  /**
+   * Obtains the statement to use to check if a URI is visited or not.
+   */
+  mozIStorageAsyncStatement* GetIsVisitedStatement();
+
   /**
    * Obtains a pointer to this service.
    */
-  static History *GetService();
+  static History* GetService();
 
   /**
    * Obtains a pointer that has had AddRef called on it.  Used by the service
    * manager only.
    */
-  static History *GetSingleton();
+  static History* GetSingleton();
 
 private:
-  ~History();
+  virtual ~History();
+
+  /**
+   * A read-only database connection used for checking if a URI is visited.
+   *
+   * @note this should only be accessed by GetIsVisistedStatement and Shutdown.
+   */
+  nsCOMPtr<mozIStorageConnection> mReadOnlyDBConn;
+
+  /**
+   * An asynchronous statement to query if a URI is visited or not.
+   *
+   * @note this should only be accessed by GetIsVisistedStatement.
+   */
+  nsCOMPtr<mozIStorageAsyncStatement> mIsVisitedStatement;
 
   /**
    * Since visits rapidly fire at once, it's very likely to have race
@@ -132,21 +152,21 @@ private:
    */
   void Shutdown();
 
-  static History *gService;
+  static History* gService;
 
   // Ensures new tasks aren't started on destruction.
   bool mShuttingDown;
 
-  typedef nsTArray<mozilla::dom::Link *> ObserverArray;
+  typedef nsTArray<mozilla::dom::Link* > ObserverArray;
 
   class KeyClass : public nsURIHashKey
   {
   public:
-    KeyClass(const nsIURI *aURI)
+    KeyClass(const nsIURI* aURI)
     : nsURIHashKey(aURI)
     {
     }
-    KeyClass(const KeyClass &aOther)
+    KeyClass(const KeyClass& aOther)
     : nsURIHashKey(aOther)
     {
       NS_NOTREACHED("Do not call me!");