MDEV-14440: Assertion `inited==RND' failed in handler::ha_rnd_end

In the function QUICK_RANGE_SELECT::init_ror_merged_scan we create a seperate handler if the handler in
head->file cannot be reused. The flag free_file tells us if we have a seperate handler or not.
There are cases where you might create a handler and then there might be a failure(running ALTER)
and then we have to revert the handler back to the original one. The code does that
but it does not reset the flag 'free_file' in this case.
Also backported f2c4180.

mysql-test/r/range_innodb.result

@@ -55,3 +55,27 @@ pk	f1	f2	f3	pk	f1	f2	f3	f4	f5
 2	6	v	NULL	14	1	q	NULL	4	q
 3	7	c	NULL	14	1	q	NULL	4	q
 drop table t1,t2;
+#
+# MDEV-14440: Server crash in in handler::ha_external_lock or Assertion `inited==RND'
+# failed in handler::ha_rnd_end upon SELECT from partitioned table
+#
+set @optimizer_switch_save= @@optimizer_switch;
+set optimizer_switch='index_merge_sort_intersection=off';
+create table t0 (a int)engine=innodb;
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (
+a int, b int, c int,
+key(a),key(b),key(c)
+)engine=innodb;
+insert into t1
+select A.a+10*B.a, A.a+10*B.a, A.a+10*B.a+100*C.a
+from t0 A, t0 B, t0 C, t0 D where D.a<5;
+set @@global.debug_dbug="+d,ha_index_init_fail";
+explain select * from t1 where a=10 and b=10;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	index_merge	a,b	a,b	5,5	NULL	1	Using intersect(a,b); Using where
+select * from t1 where a=10 and b=10;
+ERROR HY000: Table definition has changed, please retry transaction
+DROP TABLE t0,t1;
+set @@global.debug_dbug="-d";
+set @@optimizer_switch= @optimizer_switch_save;

mysql-test/t/range_innodb.test

@@ -3,6 +3,7 @@
 --echo # 
 
 --source include/have_innodb.inc
+--source include/have_debug.inc
 
 --disable_warnings
 drop table if exists t0, t1, t2;
@@ -62,3 +63,27 @@ INSERT INTO t2 VALUES (4,'q'),(NULL,'j');
 SELECT * FROM t1 AS t1_1, t1 AS t1_2, t2
 WHERE f5 = t1_2.f2 AND ( t1_1.f1 = 103 AND t1_1.f2 = 'o' OR t1_1.pk < f4 );
 drop table t1,t2;
+
+--echo #
+--echo # MDEV-14440: Server crash in in handler::ha_external_lock or Assertion `inited==RND'
+--echo # failed in handler::ha_rnd_end upon SELECT from partitioned table
+--echo #
+
+set @optimizer_switch_save= @@optimizer_switch;
+set optimizer_switch='index_merge_sort_intersection=off';
+create table t0 (a int)engine=innodb;
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (
+  a int, b int, c int,
+  key(a),key(b),key(c)
+)engine=innodb;
+insert into t1
+select A.a+10*B.a, A.a+10*B.a, A.a+10*B.a+100*C.a
+from t0 A, t0 B, t0 C, t0 D where D.a<5;
+set @@global.debug_dbug="+d,ha_index_init_fail";
+explain select * from t1 where a=10 and b=10;
+--error ER_TABLE_DEF_CHANGED
+select * from t1 where a=10 and b=10;
+DROP TABLE t0,t1;
+set @@global.debug_dbug="-d";
+set @@optimizer_switch= @optimizer_switch_save;

sql/opt_range.cc

@@ -2161,6 +2161,7 @@ int QUICK_RANGE_SELECT::init_ror_merged_scan(bool reuse_handler, MEM_ROOT *alloc
   head->column_bitmaps_set(save_read_set, save_write_set);
   delete file;
   file= save_file;
+  free_file= false;
   DBUG_RETURN(1);
 }
 
@@ -7140,6 +7141,8 @@ TRP_ROR_INTERSECT *get_best_ror_intersect(const PARAM *param, SEL_TREE *tree,
     if (ror_intersect_add(intersect, cpk_scan, TRUE) && 
         (intersect->total_cost < min_cost))
       intersect_best= intersect; //just set pointer here
+    else
+      cpk_scan= 0; // Don't use cpk_scan
   }
   else
     cpk_scan= 0;                                // Don't use cpk_scan