Use upstream method of forcing group by plan

Summary:
For debug builds, the debug variable force_lis_for_group_by can be used to force a group by plan.

Squash with: D14521084 (facebook/mysql-5.6@d19291c)

Reviewed By: george-reynya

Differential Revision: D28815653

fbshipit-source-id: 7559ea5f927

mysql-test/suite/rocksdb/r/group_min_max.result

@@ -1,4 +1,4 @@
-set global debug="+d,force_group_by";
+set global debug="+d,force_lis_for_group_by";
 drop table if exists t1;
 create table t1 (
 a1 char(64), a2 char(64), b char(16), c char(16) not null, d char(16), dummy char(248) default ' '
@@ -2679,12 +2679,12 @@ a
 BB
 EXPLAIN SELECT a FROM t1 WHERE a='AA' GROUP BY a;
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	t1	NULL	ref	PRIMARY	PRIMARY	7	const	1000	100.00	Using index
+1	SIMPLE	t1	NULL	range	PRIMARY	PRIMARY	7	NULL	501	100.00	Using where; Using index for group-by
 Warnings:
 Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 'AA') group by `test`.`t1`.`a`
 EXPLAIN SELECT a FROM t1 WHERE a='BB' GROUP BY a;
 id	select_type	table	partitions	type	possible_keys	key	key_len	ref	rows	filtered	Extra
-1	SIMPLE	t1	NULL	ref	PRIMARY	PRIMARY	7	const	1000	100.00	Using index
+1	SIMPLE	t1	NULL	range	PRIMARY	PRIMARY	7	NULL	501	100.00	Using where; Using index for group-by
 Warnings:
 Note	1003	/* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 'BB') group by `test`.`t1`.`a`
 SELECT DISTINCT a FROM t1 WHERE a='BB';
@@ -4042,4 +4042,4 @@ Handler_read_rnd	0
 Handler_read_rnd_next	0
 DROP TABLE t1;
 # End of test for Bug#18109609
-set global debug="-d,force_group_by";
+set global debug="-d,force_lis_for_group_by";

mysql-test/suite/rocksdb/t/group_min_max.test

@@ -1,8 +1,8 @@
 --source include/have_debug.inc
-set global debug="+d,force_group_by";
+set global debug="+d,force_lis_for_group_by";
 
 let $engine=RocksDB;
 --source include/group_min_max.inc
 
-set global debug="-d,force_group_by";
+set global debug="-d,force_lis_for_group_by";
 

sql/opt_range.cc

@@ -3172,15 +3172,13 @@ int test_quick_select(THD *thd, Key_map keys_to_use, table_map prev_tables,
     KEY_PART *key_parts;
     KEY *key_info;
     PARAM param;
-    bool force_group_by = false;
 
     /*
       Use the 3 multiplier as range optimizer allocates big PARAM structure
       and may evaluate a subquery expression
       TODO During the optimization phase we should evaluate only inexpensive
            single-lookup subqueries.
     */
-    DBUG_EXECUTE_IF("force_group_by", force_group_by = true;);
     uchar buff[STACK_BUFF_ALLOC];
     if (check_stack_overrun(thd, 3 * STACK_MIN_SIZE + sizeof(PARAM), buff))
       return 0;  // Fatal error flag is set
@@ -3369,13 +3367,10 @@ int test_quick_select(THD *thd, Key_map keys_to_use, table_map prev_tables,
                                    Opt_trace_context::RANGE_OPTIMIZER);
       if (unlikely(trace->is_started()))
         group_trp->trace_basic_info(&param, &grp_summary);
-      if (group_trp->cost_est < best_cost || force_group_by) {
+      if (group_trp->cost_est < best_cost) {
         grp_summary.add("chosen", true);
         best_trp = group_trp;
         best_cost = best_trp->cost_est;
-        if (force_group_by) {
-          goto force_plan;
-        }
       } else
         grp_summary.add("chosen", false).add_alnum("cause", "cost");
     }
@@ -3479,7 +3474,6 @@ int test_quick_select(THD *thd, Key_map keys_to_use, table_map prev_tables,
       }
     }
 
-  force_plan:
     thd->mem_root = param.old_root;
 
     /*