news, like imap and local mail, needs to use the db cache to make sure that when several

Open()'s happen, they get the same db object.  this fixes the problem where getting new
news wouldn't update the db listers (folder pane and thread pane, in this case.)

mailnews/db/msgdb/src/nsNewsDatabase.cpp

@@ -37,21 +37,30 @@ nsresult nsNewsDatabase::MessageDBOpenUsingURL(const char * groupURL)
   return NS_OK;
 }
 
-/* static */ 
-nsresult nsNewsDatabase::Open(nsFileSpec &newsgroupName, PRBool create, nsIMsgDatabase** pMessageDB, PRBool upgrading /*=PR_FALSE*/)
+NS_IMETHODIMP nsNewsDatabase::Open(nsFileSpec &newsgroupName, PRBool create, nsIMsgDatabase** pMessageDB, PRBool upgrading /*=PR_FALSE*/)
 {
   nsNewsDatabase	        *newsDB;
   nsNewsSummarySpec	        summarySpec(newsgroupName);
   nsresult                  err = NS_OK;
 
 #ifdef DEBUG_sspitzer
-    printf("nsNewsDatabase::Open(%s, %s, %p, %s) -> %s\n",
+  printf("nsNewsDatabase::Open(%s, %s, %p, %s) -> %s\n",
            (const char*)newsgroupName, create ? "TRUE":"FALSE",
            pMessageDB, upgrading ? "TRUE":"FALSE", (const char*)newsgroupName);
 #endif
 
+  nsFileSpec dbPath(summarySpec);
+
   *pMessageDB = nsnull;
 
+  newsDB = (nsNewsDatabase *) FindInCache(dbPath);
+  if (newsDB) {
+		*pMessageDB = newsDB;
+		//FindInCache does the AddRef'ing
+		//newsDB->AddRef();
+		return(NS_OK);
+  }
+
   newsDB = new nsNewsDatabase();
   
   if (!newsDB) {
@@ -69,19 +78,25 @@ nsresult nsNewsDatabase::Open(nsFileSpec &newsgroupName, PRBool create, nsIMsgDa
 #ifdef DEBUG_sspitzer
     printf("newsDB->OpenMDB succeeded!\n");
 #endif
-    *pMessageDB = newsDB;
+	*pMessageDB = newsDB;
+	if (newsDB) {
+		GetDBCache()->AppendElement(newsDB);
+	}
   }
-#ifdef DEBUG_sspitzer
   else {
+#ifdef DEBUG_sspitzer
     printf("newsDB->OpenMDB failed!\n");
+#endif
     *pMessageDB = nsnull;
-    delete newsDB;
+    if (newsDB) {
+		delete newsDB;
+	}
     newsDB = nsnull;
   }
-#endif
 
   return err;
 }
+
 nsresult nsNewsDatabase::Close(PRBool forceCommit)
 {
   return nsMsgDatabase::Close(forceCommit);