Removed the parameter from st_select_lex_unit::exec_recursive.

Moved checking whether the limit set for the number of iterations
when executing a recursive query has been reached from
st_select_lex_unit::exec_recursive to TABLE_LIST::fill_recursive.
Changed the name of the system variable max_recursion_level for
max_recursive_iterations.
Adjusted test cases.

mysql-test/r/cte_recursive.result

@@ -1086,7 +1086,7 @@ generation	name
 1	Mom
 2	Grandpa Bill
 2	Grandma Ann
-set statement max_recursion_level=2 for
+set statement max_recursive_iterations=1 for
 with recursive
 ancestor_ids (id, generation)
 as
@@ -1463,8 +1463,8 @@ drop table folks;
 create table t1(a int);
 insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
 explain format=json 
-with recursive T as (select a from t1 union select a+10 from T where a < 1000) 
-select  * from T;
+with recursive t as (select a from t1 union select a+10 from t where a < 1000) 
+select  * from t;
 EXPLAIN
 {
   "query_block": {
@@ -1499,7 +1499,7 @@ EXPLAIN
                     "access_type": "ALL",
                     "rows": 10,
                     "filtered": 100,
-                    "attached_condition": "(T.a < 1000)"
+                    "attached_condition": "(t.a < 1000)"
                   }
                 }
               }

mysql-test/r/mysqld--help.result

@@ -450,7 +450,7 @@ The following options may be given as the first argument:
  max_allowed_packet instead.
  --max-prepared-stmt-count=# 
  Maximum number of prepared statements in the server
- --max-recursion-level[=#] 
+ --max-recursive-iterations[=#] 
  Maximum number of iterations when executing recursive
  queries
  --max-relay-log-size=# 
@@ -1273,7 +1273,7 @@ max-join-size 18446744073709551615
 max-length-for-sort-data 1024
 max-long-data-size 4194304
 max-prepared-stmt-count 16382
-max-recursion-level 18446744073709551615
+max-recursive-iterations 18446744073709551615
 max-relay-log-size 1073741824
 max-seeks-for-key 18446744073709551615
 max-sort-length 1024

mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result

@@ -2165,7 +2165,7 @@ NUMERIC_BLOCK_SIZE	1
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
-VARIABLE_NAME	MAX_RECURSION_LEVEL
+VARIABLE_NAME	MAX_RECURSIVE_ITERATIONS
 SESSION_VALUE	4294967295
 GLOBAL_VALUE	4294967295
 GLOBAL_VALUE_ORIGIN	COMPILE-TIME

mysql-test/t/cte_recursive.test

@@ -914,7 +914,7 @@ as
 )
 select * from ancestors;
 
-set statement max_recursion_level=2 for
+set statement max_recursive_iterations=1 for
 with recursive
 ancestor_ids (id, generation)
 as
@@ -1074,8 +1074,8 @@ create table t1(a int);
 insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
  
 explain format=json 
-with recursive T as (select a from t1 union select a+10 from T where a < 1000) 
-select  * from T;
+with recursive t as (select a from t1 union select a+10 from t where a < 1000) 
+select  * from t;
 
 drop table t1;
 

sql/sql_class.h

@@ -558,7 +558,7 @@ typedef struct system_variables
   ulong max_allowed_packet;
   ulong max_error_count;
   ulong max_length_for_sort_data;
-  ulong max_recursion_level;
+  ulong max_recursive_iterations;
   ulong max_sort_length;
   ulong max_tmp_tables;
   ulong max_insert_delayed_threads;

sql/sql_cte.h

@@ -2,6 +2,7 @@
 #define SQL_CTE_INCLUDED
 #include "sql_list.h"
 #include "sql_lex.h"
+#include "sql_select.h"
 
 class select_union;
 struct st_unit_ctxt_elem;
@@ -186,6 +187,8 @@ class With_element : public Sql_alloc
 
   bool instantiate_tmp_tables();
 
+  void prepare_for_next_iteration();
+
   friend class With_clause;
 };
 
@@ -356,6 +359,19 @@ bool With_element::all_are_stabilized()
 }
 
 
+inline
+void With_element::prepare_for_next_iteration()
+{
+  With_element *with_elem= this;
+  while ((with_elem= with_elem->get_next_mutually_recursive()) != this)
+  {
+    TABLE *rec_table= with_elem->first_rec_table_to_update;
+    if (rec_table)
+      rec_table->reginfo.join_tab->preread_init_done= false;        
+  }
+}
+
+
 inline
 void  st_select_lex_unit::set_with_clause(With_clause *with_cl)
 { 

sql/sql_derived.cc

@@ -927,13 +927,18 @@ bool TABLE_LIST::fill_recursive(THD *thd)
   bool rc= false;
   st_select_lex_unit *unit= get_unit();
   if (is_with_table_recursive_reference())
-    rc= unit->exec_recursive(false);
+  {
+    rc= unit->exec_recursive();
+  }
   else
   {
     rc= with->instantiate_tmp_tables();
-    while(!rc && !with->all_are_stabilized())
+    while (!rc && !with->all_are_stabilized())
     {
-      rc= unit->exec_recursive(true);
+      if (with->level > thd->variables.max_recursive_iterations)
+        break;
+      with->prepare_for_next_iteration();
+      rc= unit->exec_recursive();
     }
     if (!rc)
     {

sql/sql_lex.h

@@ -706,7 +706,7 @@ class st_select_lex_unit: public st_select_lex_node {
   bool prepare(THD *thd, select_result *result, ulong additional_options);
   bool optimize();
   bool exec();
-  bool exec_recursive(bool is_driving_recursive);
+  bool exec_recursive();
   bool cleanup();
   inline void unclean() { cleaned= 0; }
   void reinit_exec_mechanism();

sql/sql_union.cc

@@ -1167,7 +1167,7 @@ bool st_select_lex_unit::exec()
 
 
 // One step of recursive execution
-bool st_select_lex_unit::exec_recursive(bool is_driving_recursive)
+bool st_select_lex_unit::exec_recursive()
 {
   st_select_lex *lex_select_save= thd->lex->current_select;
   st_select_lex *start= with_element->first_recursive;
@@ -1189,18 +1189,6 @@ bool st_select_lex_unit::exec_recursive(bool is_driving_recursive)
   if ((saved_error= incr_table->file->ha_delete_all_rows()))
     goto err;
 
-  if (is_driving_recursive)
-  {
-    With_element *with_elem= with_element;
-    while ((with_elem= with_elem->get_next_mutually_recursive()) !=
-            with_element)
-    {
-      rec_table= with_elem->first_rec_table_to_update;
-      if (rec_table)
-        rec_table->reginfo.join_tab->preread_init_done= false;        
-    }
-  }
-
   if (with_element->level == 0)
   {
     start= first_select();
@@ -1248,9 +1236,6 @@ bool st_select_lex_unit::exec_recursive(bool is_driving_recursive)
     if (with_element->level == 1)
       rec_table->reginfo.join_tab->preread_init_done= true;  
   }
-    
-  if (with_element->level == thd->variables.max_recursion_level)
-    with_element->set_as_stabilized();
 
   thd->lex->current_select= lex_select_save;
 err:

sql/sys_vars.cc

@@ -2145,10 +2145,10 @@ static Sys_var_ulong Sys_max_prepared_stmt_count(
        VALID_RANGE(0, 1024*1024), DEFAULT(16382), BLOCK_SIZE(1),
        &PLock_prepared_stmt_count);
 
-static Sys_var_ulong Sys_max_recursion_level(
-       "max_recursion_level",
+static Sys_var_ulong Sys_max_recursive_iterations(
+       "max_recursive_iterations",
        "Maximum number of iterations when executing recursive queries",
-       SESSION_VAR(max_recursion_level), CMD_LINE(OPT_ARG),
+       SESSION_VAR(max_recursive_iterations), CMD_LINE(OPT_ARG),
        VALID_RANGE(0, UINT_MAX), DEFAULT(UINT_MAX), BLOCK_SIZE(1));
 
 static Sys_var_ulong Sys_max_sort_length(