diff --git a/dbcon/mysql/ha_mcs_execplan.cpp b/dbcon/mysql/ha_mcs_execplan.cpp
index e23cf47e6..b01e40c16 100644
--- a/dbcon/mysql/ha_mcs_execplan.cpp
+++ b/dbcon/mysql/ha_mcs_execplan.cpp
@@ -9197,11 +9197,12 @@ int cs_get_derived_plan(ha_columnstore_derived_handler* handler, THD* /*thd*/, S
   else if (status < 0)
     return status;
 
-#ifdef DEBUG_WALK_COND
-  cerr << "---------------- cs_get_derived_plan EXECUTION PLAN ----------------" << endl;
-  cerr << *csep << endl;
-  cerr << "-------------- EXECUTION PLAN END --------------\n" << endl;
-#endif
+  if (csep->traceOn())
+  {
+    cerr << "---------------- cs_get_derived_plan EXECUTION PLAN ----------------" << endl;
+    cerr << *csep << endl;
+    cerr << "-------------- EXECUTION PLAN END --------------\n" << endl;
+  }
   // Derived table projection and filter optimization.
   derivedTableOptimization(&gwi, csep);
   return 0;
@@ -9230,25 +9231,24 @@ int cs_get_select_plan(ha_columnstore_select_handler* handler, THD* /*thd*/, SCS
   else if (status < 0)
     return status;
 
-// #ifdef DEBUG_WALK_COND
-  cerr << "---------------- cs_get_select_plan EXECUTION PLAN ----------------" << endl;
-  cerr << *csep << endl;
-  cerr << "-------------- EXECUTION PLAN END --------------\n" << endl;
-// #endif
+  if (csep->traceOn())
+  {
+    cerr << "---------------- cs_get_select_plan EXECUTION PLAN ----------------" << endl;
+    cerr << *csep << endl;
+    cerr << "-------------- EXECUTION PLAN END --------------\n" << endl;
+  }
+  
   // Derived table projection and filter optimization.
   derivedTableOptimization(&gwi, csep);
 
-  optimizer::Rule parallelCES{"parallelCES", optimizer::matchParallelCES, optimizer::applyParallelCES};
-
+  bool csepWasOptimized = optimizer::optimizeCSEP(*csep);
+  if (csep->traceOn() && csepWasOptimized)
   {
-    parallelCES.apply(*csep);
+    cerr << "---------------- cs_get_select_plan optimized EXECUTION PLAN ----------------" << endl;
+    cerr << *csep << endl;
+    cerr << "-------------- EXECUTION PLAN END --------------\n" << endl;
   }
 
-  cerr << "---------------- cs_get_select_plan rewritten EXECUTION PLAN ----------------" << endl;
-  cerr << *csep << endl;
-  cerr << "-------------- EXECUTION PLAN END --------------\n" << endl;
-  
-
   return 0;
 }
 
diff --git a/dbcon/mysql/ha_mcs_sysvars.cpp b/dbcon/mysql/ha_mcs_sysvars.cpp
index 04fdbdaed..6829877c0 100644
--- a/dbcon/mysql/ha_mcs_sysvars.cpp
+++ b/dbcon/mysql/ha_mcs_sysvars.cpp
@@ -224,7 +224,9 @@ static my_bool innodb_queries_use_mcs;
 static MYSQL_SYSVAR_BOOL(innodb_queries_use_mcs, innodb_queries_use_mcs,
                       PLUGIN_VAR_OPCMDARG | PLUGIN_VAR_READONLY,
                       "Direct all InnoDB-only queries into MCS via Select Handler.", NULL, NULL, FALSE);
-    
+static MYSQL_THDVAR_BOOL(unstable_optimizer, PLUGIN_VAR_RQCMDARG,
+                        "Apply optimizer rules after translation from SELECT_LEX/UNION", NULL, NULL, FALSE);
+                        
 st_mysql_sys_var* mcs_system_variables[] = {
     MYSQL_SYSVAR(compression_type),
     MYSQL_SYSVAR(fe_conn_info_ptr),
@@ -663,6 +665,15 @@ void set_max_allowed_in_values(THD* thd, ulong value)
   THDVAR(thd, max_allowed_in_values) = value;
 }
 
+bool get_unstable_optimizer(THD* thd)
+{
+  return (thd == NULL) ? 0 : THDVAR(thd, unstable_optimizer);
+}
+void set_unstable_optimizer(THD* thd, bool value)
+{
+  THDVAR(thd, unstable_optimizer) = value;
+}
+
 bool get_innodb_queries_uses_mcs()
 {
   return SYSVAR(innodb_queries_use_mcs);
diff --git a/dbcon/mysql/rulebased_optimizer.cpp b/dbcon/mysql/rulebased_optimizer.cpp
index f91777c7f..d3de06055 100644
--- a/dbcon/mysql/rulebased_optimizer.cpp
+++ b/dbcon/mysql/rulebased_optimizer.cpp
@@ -21,36 +21,52 @@
 
 namespace optimizer {
 
-bool Rule::apply(execplan::CalpontSelectExecutionPlan& csep)
+bool optimizeCSEPWithRules(execplan::CalpontSelectExecutionPlan& root, const std::vector<Rule>& rules) {
+
+  bool changed = false;
+  for (const auto& rule : rules)
+  {
+    changed |= rule.apply(root);
+  }
+  return changed;
+}
+
+bool optimizeCSEP(execplan::CalpontSelectExecutionPlan& root)
+{
+  optimizer::Rule parallelCES{"parallelCES", optimizer::matchParallelCES, optimizer::applyParallelCES};
+  
+  std::vector<Rule> rules = {parallelCES};
+
+  return optimizeCSEPWithRules(root, rules);
+}
+
+// DFS walk
+bool Rule::apply(execplan::CalpontSelectExecutionPlan& csep) const
 {
   bool rewrite = false;
+
   for (auto& table : csep.derivedTableList())
   {
-    auto& csepLocal = *dynamic_cast<execplan::CalpontSelectExecutionPlan*>(table.get());
-    if (matchRule(csepLocal))
+    auto* csepPtr = dynamic_cast<execplan::CalpontSelectExecutionPlan*>(table.get());
+    if (!csepPtr)
     {
-      applyRule(csepLocal);
-      rewrite = true;
-    }
-    else
-    {
-      rewrite |= apply(csepLocal);
+      continue;
     }
+
+    auto& csepLocal = *csepPtr;
+    rewrite |= apply(csepLocal);
   }
 
   for (auto& unionUnit : csep.unionVec())
   {
-    auto& unionUnitLocal = *dynamic_cast<execplan::CalpontSelectExecutionPlan*>(unionUnit.get());
+    auto* unionUnitPtr = dynamic_cast<execplan::CalpontSelectExecutionPlan*>(unionUnit.get());
+    if (!unionUnitPtr)
+    {
+      continue;
+    }
 
-    if (matchRule(unionUnitLocal))
-    {
-      applyRule(unionUnitLocal);
-      rewrite = true;
-    }
-    else
-    {
-      rewrite |= apply(unionUnitLocal);
-    }
+    auto& unionUnitLocal = *unionUnitPtr;
+    rewrite |= apply(unionUnitLocal);
   }
 
   if (matchRule(csep))
diff --git a/dbcon/mysql/rulebased_optimizer.h b/dbcon/mysql/rulebased_optimizer.h
index 3f0a3e10f..65fa3f359 100644
--- a/dbcon/mysql/rulebased_optimizer.h
+++ b/dbcon/mysql/rulebased_optimizer.h
@@ -31,10 +31,11 @@ struct Rule
   std::string name;
   bool (*matchRule)(execplan::CalpontSelectExecutionPlan&);
   void (*applyRule)(execplan::CalpontSelectExecutionPlan&);
-  bool apply(execplan::CalpontSelectExecutionPlan& csep);
+  bool apply(execplan::CalpontSelectExecutionPlan& csep) const;
 };
 
 bool matchParallelCES(execplan::CalpontSelectExecutionPlan& csep);
 void applyParallelCES(execplan::CalpontSelectExecutionPlan& csep);
+bool optimizeCSEP(execplan::CalpontSelectExecutionPlan& root);
 
 }
\ No newline at end of file