[SHOW] EXPLAIN UPDATE/DELETE, code re-structuring

- Handle statements inside SPs:
  = regular statements
  = SET command, which does not have its own statement.

- Handle execution of subquery from range optimizer: 
  allocate subquery QPFs on the same MEM_ROOT as the whole 
  query plan was allocated.

sql/opt_qpf.cc

@@ -559,8 +559,19 @@ int QPF_update::print_explain(QPF_query *query, select_result_sink *output,
   return print_explain_for_children(query, output, explain_flags);
 }
 
-void delete_qpf_query(QPF_query * query)
+
+void delete_qpf_query(LEX *lex)
+{
+  delete lex->query_plan_footprint;
+  lex->query_plan_footprint= NULL;
+}
+
+
+void create_qpf_query(LEX *lex, MEM_ROOT *mem_root)
 {
-  delete query;
+  DBUG_ASSERT(!lex->query_plan_footprint);
+  lex->query_plan_footprint= new QPF_query;
+  DBUG_ASSERT(mem_root == current_thd->mem_root);
+  lex->query_plan_footprint->mem_root= mem_root;
 }
 

sql/opt_qpf.h

@@ -214,6 +214,8 @@ public:
 
   /* Produce a tabular EXPLAIN output */
   int print_explain(select_result_sink *output, uint8 explain_flags);
+
+  MEM_ROOT *mem_root;
 private:
   QPF_union *unions[MAX_TABLES];
   QPF_select *selects[MAX_TABLES];

sql/sp_head.cc

@@ -2973,6 +2973,7 @@ sp_lex_keeper::reset_lex_and_exec_core(THD *thd, uint *nextp,
   }
 
   reinit_stmt_before_use(thd, m_lex);
+  // not here, but inside every instr: create_qpf_query(m_lex);
 
   if (open_tables)
     res= instr->exec_open_and_lock_tables(thd, m_lex->query_tables);
@@ -3007,8 +3008,7 @@ sp_lex_keeper::reset_lex_and_exec_core(THD *thd, uint *nextp,
       thd->mdl_context.release_statement_locks();
   }
   
-  delete_qpf_query(m_lex->query_plan_footprint);
-  m_lex->query_plan_footprint= NULL;
+  delete_qpf_query(m_lex);
 
   if (m_lex->query_tables_own_last)
   {
@@ -3212,6 +3212,7 @@ sp_instr_set::execute(THD *thd, uint *nextp)
 int
 sp_instr_set::exec_core(THD *thd, uint *nextp)
 {
+  create_qpf_query(thd->lex, thd->mem_root);
   int res= thd->spcont->set_variable(thd, m_offset, &m_value);
 
   if (res)
@@ -3224,6 +3225,7 @@ sp_instr_set::exec_core(THD *thd, uint *nextp)
       my_error(ER_OUT_OF_RESOURCES, MYF(ME_FATALERROR));
     }
   }
+  delete_qpf_query(thd->lex);
 
   *nextp = m_ip+1;
   return res;

sql/sql_lex.cc

@@ -4251,7 +4251,7 @@ void st_select_lex::save_qpf(QPF_query *output)
       msg= "Query plan already deleted";
     }
     set_explain_type(TRUE/* on_the_fly */);
-    QPF_select *qp_sel= new QPF_select;
+    QPF_select *qp_sel= new (output->mem_root) QPF_select;
     qp_sel->select_id= select_number;
     qp_sel->select_type= type;
     qp_sel->message= msg;
@@ -4346,7 +4346,7 @@ int st_select_lex_unit::save_qpf(QPF_query *output)
     return 0;
   }
   
-  QPF_union *qpfu= new QPF_union;
+  QPF_union *qpfu= new (output->mem_root) QPF_union;
   /*
     TODO: The following code should be eliminated. If we have a capability to
     save Query Plan Footprints, we should just save them, and never need to 
@@ -4361,7 +4361,7 @@ int st_select_lex_unit::save_qpf(QPF_query *output)
     const char *msg="Query plan already deleted";
     first->set_explain_type(TRUE/* on_the_fly */);
 
-    QPF_select *qp_sel= new QPF_select;
+    QPF_select *qp_sel= new (output->mem_root)QPF_select;
     qp_sel->select_id= first->select_number;
     qp_sel->select_type= first->type;
     qp_sel->message= msg;

sql/sql_lex.h

@@ -619,7 +619,8 @@ class select_union;
 class Procedure;
 class QPF_query;
 
-void delete_qpf_query(QPF_query * query);
+void delete_qpf_query(LEX *lex);
+void create_qpf_query(LEX *lex, MEM_ROOT *mem_root);
 
 class st_select_lex_unit: public st_select_lex_node {
 protected:

sql/sql_parse.cc

@@ -598,10 +598,7 @@ static void handle_bootstrap_impl(THD *thd)
 #if defined(ENABLED_PROFILING)
     thd->profiling.finish_current_query();
 #endif
-    //
-    delete thd->lex->query_plan_footprint;
-    thd->lex->query_plan_footprint= NULL;
-    //
+    delete_qpf_query(thd->lex);
 
     if (bootstrap_error)
       break;
@@ -1523,8 +1520,7 @@ void log_slow_statement(THD *thd)
 {
   DBUG_ENTER("log_slow_statement");
 
-  delete thd->lex->query_plan_footprint;
-  thd->lex->query_plan_footprint= NULL;
+  delete_qpf_query(thd->lex);
 
   /*
     The following should never be true with our current code base,
@@ -2188,8 +2184,7 @@ mysql_execute_command(THD *thd)
     thd->mdl_context.release_transactional_locks();
   }
   
-  DBUG_ASSERT(!thd->lex->query_plan_footprint);
-  thd->lex->query_plan_footprint= new QPF_query;
+  create_qpf_query(thd->lex, thd->mem_root);
 
 #ifndef DBUG_OFF
   if (lex->sql_command != SQLCOM_SET_OPTION)

sql/sql_prepare.cc

@@ -3927,8 +3927,7 @@ bool Prepared_statement::execute(String *expanded_query, bool open_cursor)
   if (! cursor)
     cleanup_stmt();
   //psergey: TODO the "EXECUTE problem" is here
-  delete_qpf_query(thd->lex->query_plan_footprint);
-  thd->lex->query_plan_footprint= NULL;
+  delete_qpf_query(thd->lex);
 
   thd->set_statement(&stmt_backup);
   thd->stmt_arena= old_stmt_arena;

sql/sql_select.cc

@@ -11112,6 +11112,7 @@ void JOIN::cleanup(bool full)
     if (select_lex->select_number != UINT_MAX && 
         select_lex->select_number != INT_MAX /* this is not a UNION's "fake select */ && 
         have_query_plan != QEP_NOT_PRESENT_YET && 
+        thd->lex->query_plan_footprint && // for "SET" command in SPs.
         !thd->lex->query_plan_footprint->get_select(select_lex->select_number))
     {
       const char *message= NULL;
@@ -22986,7 +22987,7 @@ int JOIN::save_qpf(QPF_query *output, bool need_tmp_table, bool need_order,
   if (message)
   {
     QPF_select *qp_sel;
-    qp_node= qp_sel= new QPF_select;
+    qp_node= qp_sel= new (output->mem_root) QPF_select;
     join->select_lex->set_explain_type(on_the_fly);
 
     qp_sel->select_id= join->select_lex->select_number;
@@ -22998,7 +22999,7 @@ int JOIN::save_qpf(QPF_query *output, bool need_tmp_table, bool need_order,
   else if (join->select_lex == join->unit->fake_select_lex)
   {
     select_lex->set_explain_type(on_the_fly);
-    QPF_union *qp_union= new QPF_union;
+    QPF_union *qp_union= new (output->mem_root) QPF_union;
     qp_node= qp_union;
 
     SELECT_LEX *child;
@@ -23018,7 +23019,7 @@ int JOIN::save_qpf(QPF_query *output, bool need_tmp_table, bool need_order,
            join->select_lex->master_unit()->derived->is_materialized_derived())
   {
     QPF_select *qp_sel;
-    qp_node= qp_sel= new QPF_select;
+    qp_node= qp_sel= new (output->mem_root) QPF_select;
     table_map used_tables=0;
 
     if (on_the_fly)
@@ -23077,7 +23078,7 @@ int JOIN::save_qpf(QPF_query *output, bool need_tmp_table, bool need_order,
         tab= pre_sort_join_tab;
       }
 
-      QPF_table_access *qpt= new QPF_table_access;
+      QPF_table_access *qpt= new (output->mem_root) QPF_table_access;
       qp_sel->add_table(qpt);
       
       /* id */