Merge

mysql-test/r/derived_opt.result

-drop table if exists t1,t2,t3;
+drop table if exists t0,t1,t2,t3;
+drop database if exists test1;
 set @exit_optimizer_switch=@@optimizer_switch;
 set optimizer_switch='derived_merge=on,derived_with_keys=on';
 set @save_optimizer_switch=@@optimizer_switch;
@@ -352,4 +353,155 @@ pk	pk
 72	72
 80	80
 drop table t1, t2, t3, t4;
+#
+# MDEV-6888: Query spends a long time in best_extension_by_limited_search with mrr enabled
+#
+create database test1;
+use test1;
+set @tmp_jcl= @@join_cache_level;
+set @tmp_os= @@optimizer_switch;
+set join_cache_level=8;
+set optimizer_switch='mrr=on,mrr_sort_keys=on';
+CREATE TABLE t0 (
+f1 bigint(20) DEFAULT NULL,
+f2 char(50) DEFAULT NULL
+) ENGINE=MEMORY DEFAULT CHARSET=latin1;
+INSERT INTO t0 VALUES (NULL,'numeric column is NULL'),(0,NULL),(5,'five'),(1,'one'),(2,'two');
+CREATE TABLE t1 (
+f1 decimal(64,30) DEFAULT NULL,
+f2 varchar(50) DEFAULT NULL
+) ENGINE=MEMORY DEFAULT CHARSET=latin1;
+INSERT INTO t1 VALUES 
+(NULL,'numeric column is NULL'),
+(0.000000000000000000000000000000,NULL),
+(5.000000000000000000000000000000,'five'),
+(1.000000000000000000000000000000,'one'),
+(3.000000000000000000000000000000,'three');
+CREATE TABLE t2 (
+f1 double DEFAULT NULL,
+f2 varbinary(50) DEFAULT NULL
+) ENGINE=MEMORY DEFAULT CHARSET=latin1;
+INSERT INTO t2 VALUES (NULL,'numeric column is NULL'),(0,NULL),(5,'five'),(2,'two'),(3,'three');
+create VIEW v0  AS select f1,f2 from t1 ;
+create VIEW v1 AS select tab1_v1.f1,tab1_v1.f2 from t1 tab1_v1 join v0 tab2 on tab1_v1.f1 = tab2.f1 and tab1_v1.f2 = tab2.f2;
+create VIEW v2 AS select tab1_v2.f1,tab1_v2.f2 from t2 tab1_v2 join v1 tab2 on tab1_v2.f1 = tab2.f1 and tab1_v2.f2 = tab2.f2;
+create VIEW v3 AS select tab1_v3.f1,tab1_v3.f2 from t0 tab1_v3 join v2 tab2 on tab1_v3.f1 = tab2.f1 and tab1_v3.f2 = tab2.f2;
+create VIEW v4 AS select tab1_v4.f1,tab1_v4.f2 from t1 tab1_v4 join v3 tab2 on tab1_v4.f1 = tab2.f1 and tab1_v4.f2 = tab2.f2;
+create VIEW v5 AS select tab1_v5.f1,tab1_v5.f2 from t2 tab1_v5 join v4 tab2 on tab1_v5.f1 = tab2.f1 and tab1_v5.f2 = tab2.f2;
+create VIEW v6 AS select tab1_v6.f1,tab1_v6.f2 from t0 tab1_v6 join v5 tab2 on tab1_v6.f1 = tab2.f1 and tab1_v6.f2 = tab2.f2;
+create VIEW v7 AS select tab1_v7.f1,tab1_v7.f2 from t1 tab1_v7 join v6 tab2 on tab1_v7.f1 = tab2.f1 and tab1_v7.f2 = tab2.f2;
+create VIEW v8 AS select tab1_v8.f1,tab1_v8.f2 from t2 tab1_v8 join v7 tab2 on tab1_v8.f1 = tab2.f1 and tab1_v8.f2 = tab2.f2;
+create VIEW v9 AS select tab1_v9.f1,tab1_v9.f2 from t0 tab1_v9 join v8 tab2 on tab1_v9.f1 = tab2.f1 and tab1_v9.f2 = tab2.f2;
+create VIEW v10 AS select tab1_v10.f1,tab1_v10.f2 from t1 tab1_v10 join v9 tab2 on tab1_v10.f1 = tab2.f1 and tab1_v10.f2 = tab2.f2;
+create VIEW v11 AS select tab1_v11.f1,tab1_v11.f2 from t2 tab1_v11 join v10 tab2 on tab1_v11.f1 = tab2.f1 and tab1_v11.f2 = tab2.f2;
+create VIEW v12 AS select tab1_v12.f1,tab1_v12.f2 from t0 tab1_v12 join v11 tab2 on tab1_v12.f1 = tab2.f1 and tab1_v12.f2 = tab2.f2;
+create VIEW v13 AS select tab1_v13.f1,tab1_v13.f2 from t1 tab1_v13 join v12 tab2 on tab1_v13.f1 = tab2.f1 and tab1_v13.f2 = tab2.f2;
+create VIEW v14 AS select tab1_v14.f1,tab1_v14.f2 from t2 tab1_v14 join v13 tab2 on tab1_v14.f1 = tab2.f1 and tab1_v14.f2 = tab2.f2;
+create VIEW v15 AS select tab1_v15.f1,tab1_v15.f2 from t0 tab1_v15 join v14 tab2 on tab1_v15.f1 = tab2.f1 and tab1_v15.f2 = tab2.f2;
+create VIEW v16 AS select tab1_v16.f1,tab1_v16.f2 from t1 tab1_v16 join v15 tab2 on tab1_v16.f1 = tab2.f1 and tab1_v16.f2 = tab2.f2;
+create VIEW v17 AS select tab1_v17.f1,tab1_v17.f2 from t2 tab1_v17 join v16 tab2 on tab1_v17.f1 = tab2.f1 and tab1_v17.f2 = tab2.f2;
+create VIEW v18 AS select tab1_v18.f1,tab1_v18.f2 from t0 tab1_v18 join v17 tab2 on tab1_v18.f1 = tab2.f1 and tab1_v18.f2 = tab2.f2;
+create VIEW v19 AS select tab1_v19.f1,tab1_v19.f2 from t1 tab1_v19 join v18 tab2 on tab1_v19.f1 = tab2.f1 and tab1_v19.f2 = tab2.f2;
+create VIEW v20 AS select tab1_v20.f1,tab1_v20.f2 from t2 tab1_v20 join v19 tab2 on tab1_v20.f1 = tab2.f1 and tab1_v20.f2 = tab2.f2;
+create VIEW v21 AS select tab1_v21.f1,tab1_v21.f2 from t0 tab1_v21 join v20 tab2 on tab1_v21.f1 = tab2.f1 and tab1_v21.f2 = tab2.f2;
+create VIEW v22 AS select tab1_v22.f1,tab1_v22.f2 from t1 tab1_v22 join v21 tab2 on tab1_v22.f1 = tab2.f1 and tab1_v22.f2 = tab2.f2;
+create VIEW v23 AS select tab1_v23.f1,tab1_v23.f2 from t2 tab1_v23 join v22 tab2 on tab1_v23.f1 = tab2.f1 and tab1_v23.f2 = tab2.f2;
+create VIEW v24 AS select tab1_v24.f1,tab1_v24.f2 from t0 tab1_v24 join v23 tab2 on tab1_v24.f1 = tab2.f1 and tab1_v24.f2 = tab2.f2;
+create VIEW v25 AS select tab1_v25.f1,tab1_v25.f2 from t1 tab1_v25 join v24 tab2 on tab1_v25.f1 = tab2.f1 and tab1_v25.f2 = tab2.f2;
+create VIEW v26 AS select tab1_v26.f1,tab1_v26.f2 from t2 tab1_v26 join v25 tab2 on tab1_v26.f1 = tab2.f1 and tab1_v26.f2 = tab2.f2;
+create VIEW v27 AS select tab1_v27.f1,tab1_v27.f2 from t0 tab1_v27 join v26 tab2 on tab1_v27.f1 = tab2.f1 and tab1_v27.f2 = tab2.f2;
+EXPLAIN SELECT CAST(f1 AS SIGNED INTEGER) AS f1, CAST(f2 AS CHAR) AS f2 FROM v27;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	tab1_v27	ALL	NULL	NULL	NULL	NULL	5	Using where
+1	SIMPLE	tab1_v26	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v27.f1,test1.tab1_v27.f2	5	Using where; Using join buffer (flat, BNLH join)
+1	SIMPLE	tab1_v25	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v26.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v24	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v25.f1,test1.tab1_v25.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v23	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v24.f1,test1.tab1_v24.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v22	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v23.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v21	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v22.f1,test1.tab1_v22.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v20	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v21.f1,test1.tab1_v21.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v19	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v20.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v18	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v19.f1,test1.tab1_v19.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v17	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v18.f1,test1.tab1_v18.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v16	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v17.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v15	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v16.f1,test1.tab1_v16.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v14	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v15.f1,test1.tab1_v15.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v13	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v14.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v12	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v13.f1,test1.tab1_v13.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v11	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v12.f1,test1.tab1_v12.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v10	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v11.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v9	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v10.f1,test1.tab1_v10.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v8	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v9.f1,test1.tab1_v9.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v7	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v8.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v6	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v7.f1,test1.tab1_v7.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v5	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v6.f1,test1.tab1_v6.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v4	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v5.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v3	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v4.f1,test1.tab1_v4.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v2	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v3.f1,test1.tab1_v3.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v1	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v2.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	t1	hash_ALL	NULL	#hash#$hj	85	test1.tab1_v1.f1,test1.tab1_v1.f2	5	Using where; Using join buffer (incremental, BNLH join)
+# This used to hang forever:
+EXPLAIN SELECT CAST(f1 AS SIGNED INTEGER) AS f1, CAST(f2 AS CHAR) AS f2 FROM v27;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	tab1_v27	ALL	NULL	NULL	NULL	NULL	5	Using where
+1	SIMPLE	tab1_v26	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v27.f1,test1.tab1_v27.f2	5	Using where; Using join buffer (flat, BNLH join)
+1	SIMPLE	tab1_v25	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v26.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v24	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v25.f1,test1.tab1_v25.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v23	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v24.f1,test1.tab1_v24.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v22	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v23.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v21	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v22.f1,test1.tab1_v22.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v20	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v21.f1,test1.tab1_v21.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v19	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v20.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v18	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v19.f1,test1.tab1_v19.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v17	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v18.f1,test1.tab1_v18.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v16	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v17.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v15	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v16.f1,test1.tab1_v16.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v14	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v15.f1,test1.tab1_v15.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v13	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v14.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v12	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v13.f1,test1.tab1_v13.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v11	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v12.f1,test1.tab1_v12.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v10	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v11.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v9	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v10.f1,test1.tab1_v10.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v8	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v9.f1,test1.tab1_v9.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v7	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v8.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v6	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v7.f1,test1.tab1_v7.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v5	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v6.f1,test1.tab1_v6.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v4	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v5.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v3	hash_ALL	NULL	#hash#$hj	60	test1.tab1_v4.f1,test1.tab1_v4.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v2	hash_ALL	NULL	#hash#$hj	63	test1.tab1_v3.f1,test1.tab1_v3.f2	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	tab1_v1	hash_ALL	NULL	#hash#$hj	31	test1.tab1_v2.f1	5	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	t1	hash_ALL	NULL	#hash#$hj	85	test1.tab1_v1.f1,test1.tab1_v1.f2	5	Using where; Using join buffer (incremental, BNLH join)
+use test;
+drop database test1;
+set join_cache_level=@tmp_jcl;
+set optimizer_switch=@tmp_os;
+#
+# MDEV-6879: Dereference of NULL primary_file->table in DsMrr_impl::get_disk_sweep_mrr_cost()
+#
+create table t1(a int);
+insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t2 (a int, b int, c text);
+insert into t2
+select
+A.a + B.a* 10,
+A.a + B.a* 10,
+'blob-data'
+from t1 A, t1 B;
+set @tmp_jcl= @@join_cache_level;
+set @tmp_os= @@optimizer_switch;
+set join_cache_level=6;
+set @@optimizer_switch='derived_merge=on,derived_with_keys=on,mrr=on';
+explain
+select * from
+t1 join
+(select * from t2 order by a limit 1000) as D1
+where
+D1.a= t1.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	10	Using where
+1	PRIMARY	<derived2>	hash_ALL	key0	#hash#key0	5	test.t1.a	100	Using join buffer (flat, BNLH join)
+2	DERIVED	t2	ALL	NULL	NULL	NULL	NULL	100	Using filesort
+set join_cache_level=@tmp_jcl;
+set optimizer_switch=@tmp_os;
+drop table t1, t2;
 set optimizer_switch=@exit_optimizer_switch;

mysql-test/r/innodb_mrr_cpk.result

@@ -149,3 +149,41 @@ set @@join_cache_level= @save_join_cache_level;
 set storage_engine=@save_storage_engine;
 set optimizer_switch=@innodb_mrr_cpk_tmp;
 drop table t0;
+#
+# MDEV-6878: Use of uninitialized saved_primary_key in Mrr_ordered_index_reader::resume_read()
+#
+create table t0(a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (
+pk varchar(32) character set utf8 primary key,
+kp1 char(32) not null,
+col1 varchar(32),
+key (kp1)
+) engine=innodb;
+insert into t1
+select
+concat('pk-', 1000 +A.a),
+concat('kp1-', 1000 +A.a),
+concat('val-', 1000 +A.a)
+from test.t0 A ;
+create table t2 as select kp1 as a from t1;
+set join_cache_level=8;
+set optimizer_switch='mrr=on,mrr_sort_keys=on';
+explain
+select * from t2 straight_join t1 force index(kp1) where t1.kp1=t2.a;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	10	
+1	SIMPLE	t1	ref	kp1	kp1	32	test.t2.a	1	Using join buffer (flat, BKAH join); Key-ordered Rowid-ordered scan
+select * from t2 straight_join t1 force index(kp1) where t1.kp1=t2.a;
+a	pk	kp1	col1
+kp1-1000	pk-1000	kp1-1000	val-1000
+kp1-1001	pk-1001	kp1-1001	val-1001
+kp1-1002	pk-1002	kp1-1002	val-1002
+kp1-1003	pk-1003	kp1-1003	val-1003
+kp1-1004	pk-1004	kp1-1004	val-1004
+kp1-1005	pk-1005	kp1-1005	val-1005
+kp1-1006	pk-1006	kp1-1006	val-1006
+kp1-1007	pk-1007	kp1-1007	val-1007
+kp1-1008	pk-1008	kp1-1008	val-1008
+kp1-1009	pk-1009	kp1-1009	val-1009
+drop table t0,t1,t2;

mysql-test/r/join_cache.result

@@ -498,8 +498,8 @@ CountryLanguage.Percentage > 50 AND
 LENGTH(Language) < LENGTH(City.Name) - 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	Country	ALL	NULL	NULL	NULL	NULL	239	Using where
-1	SIMPLE	City	ALL	NULL	NULL	NULL	NULL	4079	Using where; Using join buffer (flat, BNL join)
 1	SIMPLE	CountryLanguage	ALL	NULL	NULL	NULL	NULL	984	Using where; Using join buffer (flat, BNL join)
+1	SIMPLE	City	ALL	NULL	NULL	NULL	NULL	4079	Using where; Using join buffer (flat, BNL join)
 SELECT City.Name, Country.Name, CountryLanguage.Language
 FROM City,Country,CountryLanguage
 WHERE City.Country=Country.Code AND
@@ -576,8 +576,8 @@ CountryLanguage.Percentage > 50 AND
 LENGTH(Language) < LENGTH(City.Name) - 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	Country	ALL	NULL	NULL	NULL	NULL	239	Using where
-1	SIMPLE	City	ALL	NULL	NULL	NULL	NULL	4079	Using where; Using join buffer (flat, BNL join)
-1	SIMPLE	CountryLanguage	ALL	NULL	NULL	NULL	NULL	984	Using where; Using join buffer (incremental, BNL join)
+1	SIMPLE	CountryLanguage	ALL	NULL	NULL	NULL	NULL	984	Using where; Using join buffer (flat, BNL join)
+1	SIMPLE	City	ALL	NULL	NULL	NULL	NULL	4079	Using where; Using join buffer (incremental, BNL join)
 SELECT City.Name, Country.Name, CountryLanguage.Language
 FROM City,Country,CountryLanguage
 WHERE City.Country=Country.Code AND
@@ -654,8 +654,8 @@ CountryLanguage.Percentage > 50 AND
 LENGTH(Language) < LENGTH(City.Name) - 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	Country	ALL	NULL	NULL	NULL	NULL	239	Using where
-1	SIMPLE	City	hash_ALL	NULL	#hash#$hj	3	world.Country.Code	4079	Using where; Using join buffer (flat, BNLH join)
 1	SIMPLE	CountryLanguage	hash_ALL	NULL	#hash#$hj	3	world.Country.Code	984	Using where; Using join buffer (flat, BNLH join)
+1	SIMPLE	City	hash_ALL	NULL	#hash#$hj	3	world.Country.Code	4079	Using where; Using join buffer (flat, BNLH join)
 SELECT City.Name, Country.Name, CountryLanguage.Language
 FROM City,Country,CountryLanguage
 WHERE City.Country=Country.Code AND
@@ -732,8 +732,8 @@ CountryLanguage.Percentage > 50 AND
 LENGTH(Language) < LENGTH(City.Name) - 2;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	Country	ALL	NULL	NULL	NULL	NULL	239	Using where
-1	SIMPLE	City	hash_ALL	NULL	#hash#$hj	3	world.Country.Code	4079	Using where; Using join buffer (flat, BNLH join)
-1	SIMPLE	CountryLanguage	hash_ALL	NULL	#hash#$hj	3	world.Country.Code	984	Using where; Using join buffer (incremental, BNLH join)
+1	SIMPLE	CountryLanguage	hash_ALL	NULL	#hash#$hj	3	world.Country.Code	984	Using where; Using join buffer (flat, BNLH join)
+1	SIMPLE	City	hash_ALL	NULL	#hash#$hj	3	world.Country.Code	4079	Using where; Using join buffer (incremental, BNLH join)
 SELECT City.Name, Country.Name, CountryLanguage.Language
 FROM City,Country,CountryLanguage
 WHERE City.Country=Country.Code AND

mysql-test/t/derived_opt.test

 # Initialize
 --disable_warnings
-drop table if exists t1,t2,t3;
+drop table if exists t0,t1,t2,t3;
+drop database if exists test1;
 --enable_warnings
 
 set @exit_optimizer_switch=@@optimizer_switch;
@@ -272,5 +273,95 @@ limit 10;
 
 drop table t1, t2, t3, t4;
 
+--echo #
+--echo # MDEV-6888: Query spends a long time in best_extension_by_limited_search with mrr enabled
+--echo #
+create database test1;
+use test1;
+
+set @tmp_jcl= @@join_cache_level;
+set @tmp_os= @@optimizer_switch;
+set join_cache_level=8;
+set optimizer_switch='mrr=on,mrr_sort_keys=on';
+
+CREATE TABLE t0 (
+  f1 bigint(20) DEFAULT NULL,
+  f2 char(50) DEFAULT NULL
+) ENGINE=MEMORY DEFAULT CHARSET=latin1;
+INSERT INTO t0 VALUES (NULL,'numeric column is NULL'),(0,NULL),(5,'five'),(1,'one'),(2,'two');
+
+CREATE TABLE t1 (
+  f1 decimal(64,30) DEFAULT NULL,
+  f2 varchar(50) DEFAULT NULL
+) ENGINE=MEMORY DEFAULT CHARSET=latin1;
+
+INSERT INTO t1 VALUES 
+(NULL,'numeric column is NULL'),
+(0.000000000000000000000000000000,NULL),
+(5.000000000000000000000000000000,'five'),
+(1.000000000000000000000000000000,'one'),
+(3.000000000000000000000000000000,'three');
+
+CREATE TABLE t2 (
+  f1 double DEFAULT NULL,
+  f2 varbinary(50) DEFAULT NULL
+) ENGINE=MEMORY DEFAULT CHARSET=latin1;
+INSERT INTO t2 VALUES (NULL,'numeric column is NULL'),(0,NULL),(5,'five'),(2,'two'),(3,'three');
+
+create VIEW v0  AS select f1,f2 from t1 ;
+
+let $cnt= 27; 
+while ($cnt)
+{
+# i runs from 1 to 27
+  let $i= `select 28 - $cnt`;
+  let $prev=`select $i - 1`;
+
+# rem = i mod 3
+  let $rem= `select MOD($i, 3)`;
+# view uses $i, $prev and $rem:
+  eval create VIEW v$i AS select tab1_v$i.f1,tab1_v$i.f2 from t$rem tab1_v$i join v$prev tab2 on tab1_v$i.f1 = tab2.f1 and tab1_v$i.f2 = tab2.f2;
+  dec $cnt;
+}
+
+EXPLAIN SELECT CAST(f1 AS SIGNED INTEGER) AS f1, CAST(f2 AS CHAR) AS f2 FROM v27;
+--echo # This used to hang forever:
+EXPLAIN SELECT CAST(f1 AS SIGNED INTEGER) AS f1, CAST(f2 AS CHAR) AS f2 FROM v27;
+
+use test;
+drop database test1;
+set join_cache_level=@tmp_jcl;
+set optimizer_switch=@tmp_os;
+
+
+--echo #
+--echo # MDEV-6879: Dereference of NULL primary_file->table in DsMrr_impl::get_disk_sweep_mrr_cost()
+--echo #
+create table t1(a int);
+insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+
+create table t2 (a int, b int, c text);
+insert into t2
+select
+  A.a + B.a* 10,
+  A.a + B.a* 10,
+  'blob-data'
+from t1 A, t1 B;
+
+set @tmp_jcl= @@join_cache_level;
+set @tmp_os= @@optimizer_switch;
+set join_cache_level=6;
+set @@optimizer_switch='derived_merge=on,derived_with_keys=on,mrr=on';
+explain
+select * from
+  t1 join
+  (select * from t2 order by a limit 1000) as D1
+where
+  D1.a= t1.a;
+
+set join_cache_level=@tmp_jcl;
+set optimizer_switch=@tmp_os;
+drop table t1, t2;
+
 # The following command must be the last one the file 
 set optimizer_switch=@exit_optimizer_switch;

mysql-test/t/innodb_mrr_cpk.test

@@ -139,3 +139,32 @@ set storage_engine=@save_storage_engine;
 set optimizer_switch=@innodb_mrr_cpk_tmp;
 drop table t0;
 
+--echo #
+--echo # MDEV-6878: Use of uninitialized saved_primary_key in Mrr_ordered_index_reader::resume_read()
+--echo #
+create table t0(a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+
+create table t1 (
+  pk varchar(32) character set utf8 primary key,
+  kp1 char(32) not null,
+  col1 varchar(32),
+  key (kp1)
+) engine=innodb;
+
+insert into t1
+select
+  concat('pk-', 1000 +A.a),
+  concat('kp1-', 1000 +A.a),
+  concat('val-', 1000 +A.a)
+from test.t0 A ;
+
+create table t2 as select kp1 as a from t1;
+
+set join_cache_level=8;
+set optimizer_switch='mrr=on,mrr_sort_keys=on';
+explain
+select * from t2 straight_join t1 force index(kp1) where t1.kp1=t2.a;
+select * from t2 straight_join t1 force index(kp1) where t1.kp1=t2.a;
+
+drop table t0,t1,t2;

sql/multi_range_read.cc

@@ -410,6 +410,7 @@ bool Mrr_ordered_index_reader::set_interruption_temp_buffer(uint rowid_length,
   *space_start += key_len;
 
   have_saved_rowid= FALSE;
+  read_was_interrupted= FALSE;
   return FALSE;
 }
 
@@ -418,6 +419,7 @@ void Mrr_ordered_index_reader::set_no_interruption_temp_buffer()
   support_scan_interruptions= FALSE;
   saved_key_tuple= saved_rowid= saved_primary_key= NULL; /* safety */
   have_saved_rowid= FALSE;
+  read_was_interrupted= FALSE;
 }
 
 void Mrr_ordered_index_reader::interrupt_read()
@@ -435,6 +437,7 @@ void Mrr_ordered_index_reader::interrupt_read()
              &table->key_info[table->s->primary_key],
              table->key_info[table->s->primary_key].key_length);
   }
+  read_was_interrupted= TRUE;
 
   /* Save the last rowid */
   memcpy(saved_rowid, file->ref, file->ref_length);
@@ -452,6 +455,10 @@ void Mrr_ordered_index_reader::position()
 void Mrr_ordered_index_reader::resume_read()
 {
   TABLE *table= file->get_table();
+
+  if (!read_was_interrupted)
+    return;
+
   KEY *used_index= &table->key_info[file->active_index];
   key_restore(table->record[0], saved_key_tuple, 
               used_index, used_index->key_length);
@@ -541,8 +548,7 @@ int Mrr_ordered_index_reader::init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
   is_mrr_assoc=    !test(mode & HA_MRR_NO_ASSOCIATION);
   mrr_funcs= *seq_funcs;
   source_exhausted= FALSE;
-  if (support_scan_interruptions)
-    bzero(saved_key_tuple, key_info->key_length);
+  read_was_interrupted= false;
   have_saved_rowid= FALSE;
   return 0;
 }

sql/multi_range_read.h

@@ -324,6 +324,12 @@ class Mrr_ordered_index_reader : public Mrr_index_reader
   uchar *saved_key_tuple; /* Saved current key tuple */
   uchar *saved_primary_key; /* Saved current primary key tuple */
 
+  /*
+    TRUE<=> saved_key_tuple (and saved_primary_key when applicable) have
+    valid values.
+  */
+  bool read_was_interrupted;
+
   static int compare_keys(void* arg, uchar* key1, uchar* key2);
   static int compare_keys_reverse(void* arg, uchar* key1, uchar* key2);
   

sql/sql_select.cc

@@ -9663,6 +9663,19 @@ uint check_join_cache_usage(JOIN_TAB *tab,
       cache_level--;
   }
     
+  /*
+    Don't use BKA for materialized tables. We could actually have a
+    meaningful use of BKA when linked join buffers are used.
+
+    The problem is, the temp.table is not filled (actually not even opened
+    properly) yet, and this doesn't let us call
+    handler->multi_range_read_info(). It is possible to come up with
+    estimates, etc. without acessing the table, but it seems not to worth the
+    effort now.
+  */
+  if (tab->table->pos_in_table_list->is_materialized_derived())
+    no_bka_cache= true;
+
   /*
     Don't use join buffering if we're dictated not to by no_jbuf_after
     (This is not meaningfully used currently)
@@ -9729,7 +9742,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
     if (tab->ref.is_access_triggered())
       goto no_join_cache;
       
-    if (!tab->is_ref_for_hash_join())
+    if (!tab->is_ref_for_hash_join() && !no_bka_cache)
     {
       flags= HA_MRR_NO_NULL_ENDPOINTS | HA_MRR_SINGLE_POINT;
       if (tab->table->covering_keys.is_set(tab->ref.key))

sql/table.cc

@@ -5401,7 +5401,6 @@ void TABLE::create_key_part_by_field(KEY *keyinfo,
                                      KEY_PART_INFO *key_part_info,
                                      Field *field, uint fieldnr)
 {   
-  field->flags|= PART_KEY_FLAG;
   key_part_info->null_bit= field->null_bit;
   key_part_info->null_offset= (uint) (field->null_ptr -
                                       (uchar*) record[0]);
@@ -5552,6 +5551,7 @@ bool TABLE::add_tmp_key(uint key, uint key_parts,
       (*reg_field)->key_start.set_bit(key);
     (*reg_field)->part_of_key.set_bit(key);
     create_key_part_by_field(keyinfo, key_part_info, *reg_field, fld_idx+1);
+    (*reg_field)->flags|= PART_KEY_FLAG;
     key_start= FALSE;
     key_part_info++;
   }