Fixed a deadlock related to very large temporary result sets.

h2/src/main/org/h2/result/ResultTempTable.java

@@ -155,22 +155,20 @@ public class ResultTempTable implements ResultExternal {
             table.truncate(session);
             Database database = session.getDatabase();
             synchronized (database) {
-                if (!database.isSysTableLocked()) {
-                    Session sysSession = database.getSystemSession();
                 // This session may not lock the sys table (except if it already has locked it)
                 // because it must be committed immediately,
                 // otherwise other threads can not access the sys table.
                 // If the table is not removed now, it will be when the database
                 // is opened the next time.
                 // (the table is truncated, so this is just one record)
-                    synchronized (sysSession) {
+                if (!database.isSysTableLocked()) {
+                    Session sysSession = database.getSystemSession();
                     index.removeChildrenAndResources(sysSession);
                     table.removeChildrenAndResources(sysSession);
                     // the transaction must be committed immediately
                     sysSession.commit(false);
                 }
             }
-            }
         } finally {
             table = null;
         }