MDEV-11640 gcol.gcol_select_myisam fails in buildbot on Power

JOIN_CACHE's were initialized in  check_join_cache_usage()
from make_join_readinfo(). After that make_join_readinfo() was looking
whether it's possible to use keyread. Later, after make_join_readinfo(),
optimizer decided whether to use filesort. And even later, at the
execution time, from join_read_first(), keyread was actually enabled.

The problem is, that if a query uses a vcol, base columns that it
depends on are automatically added to the read_set - because they're
needed to calculate the vcol. But if we're doing keyread, vcol is taken
from the index, not calculated, and base columns do not need to  be
in the read set (even should not be - as they aren't getting values).

The bug was that JOIN_CACHE used read_set with base columns,
they were not read because of keyread, so it was caching garbage.

So read_set is only known after the keyread was decided. And after the
filesort was decided, as filesort doesn't use keyread. But
check_join_cache_usage() needs to be done in make_join_readinfo(),
as the code below depends on these checks,

Fix: keep JOIN_CACHE checks where they were, but move initialization
down to the very end of JOIN::optimize_inner. If keyread was enabled,
update the read_set to include only columns that are part of the index.
Copy the keyread logic from join_read_first() to happen at optimize time.

mysql-test/r/join_cache.result

@@ -4450,7 +4450,7 @@ EXPLAIN
 SELECT t2.i FROM t1,t2 WHERE t1.cu = t2.cl ;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t1	hash_index	cu	#hash#cu:cu	33:33	func	10	Using where; Using join buffer (flat, BNLH join)
+1	SIMPLE	t1	hash_index	cu	#hash#cu:cu	33:33	func	10	Using where; Using index; Using join buffer (flat, BNLH join)
 SELECT t2.i FROM t1,t2 WHERE t1.cu = t2.cl ;
 i
 6
@@ -5242,7 +5242,7 @@ EXPLAIN
 SELECT * FROM t1 WHERE (t1.b) IN (SELECT c FROM t2);
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
-1	PRIMARY	t2	hash_index	c	#hash#c:c	5:5	test.t1.b	8	Start temporary; End temporary; Using join buffer (flat, BNLH join)
+1	PRIMARY	t2	hash_index	c	#hash#c:c	5:5	test.t1.b	8	Using index; Start temporary; End temporary; Using join buffer (flat, BNLH join)
 SELECT * FROM t1 WHERE (t1.b) IN (SELECT c FROM t2);
 a	b
 3914	17

mysql-test/r/join_outer.result

@@ -2006,7 +2006,7 @@ SELECT * FROM (t2 LEFT JOIN t1 ON t1.b = t2.b) JOIN t3 ON t1.b = t3.b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
 1	SIMPLE	t3	hash_ALL	PRIMARY	#hash#PRIMARY	4	test.t1.b	10	10.00	Using join buffer (flat, BNLH join)
-1	SIMPLE	t2	hash_index	PRIMARY	#hash#PRIMARY:PRIMARY	4:4	test.t1.b	27	3.70	Using join buffer (incremental, BNLH join)
+1	SIMPLE	t2	hash_index	PRIMARY	#hash#PRIMARY:PRIMARY	4:4	test.t1.b	27	3.70	Using index; Using join buffer (incremental, BNLH join)
 Warnings:
 Note	1003	select `test`.`t2`.`b` AS `b`,`test`.`t1`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b` from `test`.`t2` join `test`.`t1` join `test`.`t3` where `test`.`t3`.`b` = `test`.`t1`.`b` and `test`.`t2`.`b` = `test`.`t1`.`b`
 PREPARE stmt FROM

mysql-test/r/join_outer_jcl6.result

@@ -2017,7 +2017,7 @@ SELECT * FROM (t2 LEFT JOIN t1 ON t1.b = t2.b) JOIN t3 ON t1.b = t3.b;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	filtered	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	100.00	
 1	SIMPLE	t3	hash_ALL	PRIMARY	#hash#PRIMARY	4	test.t1.b	10	10.00	Using join buffer (flat, BNLH join)
-1	SIMPLE	t2	hash_index	PRIMARY	#hash#PRIMARY:PRIMARY	4:4	test.t1.b	27	3.70	Using join buffer (incremental, BNLH join)
+1	SIMPLE	t2	hash_index	PRIMARY	#hash#PRIMARY:PRIMARY	4:4	test.t1.b	27	3.70	Using index; Using join buffer (incremental, BNLH join)
 Warnings:
 Note	1003	select `test`.`t2`.`b` AS `b`,`test`.`t1`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b` from `test`.`t2` join `test`.`t1` join `test`.`t3` where `test`.`t3`.`b` = `test`.`t1`.`b` and `test`.`t2`.`b` = `test`.`t1`.`b`
 PREPARE stmt FROM

mysql-test/r/limit_rows_examined.result

@@ -752,15 +752,15 @@ LIMIT ROWS EXAMINED 120;
 ERROR HY000: Sort aborted: 
 SHOW STATUS LIKE 'Handler_read%';
 Variable_name	Value
-Handler_read_first	0
+Handler_read_first	1
 Handler_read_key	5
 Handler_read_last	0
-Handler_read_next	0
+Handler_read_next	7
 Handler_read_prev	0
 Handler_read_retry	0
 Handler_read_rnd	0
 Handler_read_rnd_deleted	0
-Handler_read_rnd_next	46
+Handler_read_rnd_next	38
 SHOW STATUS LIKE 'Handler_tmp%';
 Variable_name	Value
 Handler_tmp_update	0
@@ -777,15 +777,15 @@ Warnings:
 Warning	1931	Query execution was interrupted. The query examined at least 125 rows, which exceeds LIMIT ROWS EXAMINED (124). The query result may be incomplete
 SHOW STATUS LIKE 'Handler_read%';
 Variable_name	Value
-Handler_read_first	0
+Handler_read_first	1
 Handler_read_key	5
 Handler_read_last	0
-Handler_read_next	0
+Handler_read_next	7
 Handler_read_prev	0
 Handler_read_retry	0
 Handler_read_rnd	2
 Handler_read_rnd_deleted	1
-Handler_read_rnd_next	47
+Handler_read_rnd_next	39
 SHOW STATUS LIKE 'Handler_tmp%';
 Variable_name	Value
 Handler_tmp_update	0

mysql-test/r/subselect_cache.result

@@ -2842,70 +2842,70 @@ WHERE table1 .`col_varchar_key` )	field10
 1	NULL	w
 1	NULL	y
 Warnings:
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'o'
-Warning	1292	Truncated incorrect DOUBLE value: 'o'
-Warning	1292	Truncated incorrect DOUBLE value: 'o'
-Warning	1292	Truncated incorrect DOUBLE value: 'o'
-Warning	1292	Truncated incorrect DOUBLE value: 'o'
-Warning	1292	Truncated incorrect DOUBLE value: 'o'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
 SET @@optimizer_switch='subquery_cache=on';
 /* cache is on */ SELECT COUNT( DISTINCT table2 .`col_int_key` ) , (
 SELECT SUBQUERY2_t1 .`col_int_key`
@@ -2933,32 +2933,32 @@ WHERE table1 .`col_varchar_key` )	field10
 1	NULL	w
 1	NULL	y
 Warnings:
-Warning	1292	Truncated incorrect DOUBLE value: 'r'
+Warning	1292	Truncated incorrect DOUBLE value: 'a'
+Warning	1292	Truncated incorrect DOUBLE value: 'b'
 Warning	1292	Truncated incorrect DOUBLE value: 'c'
-Warning	1292	Truncated incorrect DOUBLE value: 'o'
 Warning	1292	Truncated incorrect DOUBLE value: 'd'
-Warning	1292	Truncated incorrect DOUBLE value: 'v'
-Warning	1292	Truncated incorrect DOUBLE value: 'm'
-Warning	1292	Truncated incorrect DOUBLE value: 'j'
+Warning	1292	Truncated incorrect DOUBLE value: 'e'
 Warning	1292	Truncated incorrect DOUBLE value: 'f'
-Warning	1292	Truncated incorrect DOUBLE value: 'n'
-Warning	1292	Truncated incorrect DOUBLE value: 'z'
+Warning	1292	Truncated incorrect DOUBLE value: 'g'
 Warning	1292	Truncated incorrect DOUBLE value: 'h'
+Warning	1292	Truncated incorrect DOUBLE value: 'i'
+Warning	1292	Truncated incorrect DOUBLE value: 'j'
+Warning	1292	Truncated incorrect DOUBLE value: 'k'
+Warning	1292	Truncated incorrect DOUBLE value: 'l'
+Warning	1292	Truncated incorrect DOUBLE value: 'm'
+Warning	1292	Truncated incorrect DOUBLE value: 'n'
+Warning	1292	Truncated incorrect DOUBLE value: 'o'
+Warning	1292	Truncated incorrect DOUBLE value: 'p'
 Warning	1292	Truncated incorrect DOUBLE value: 'q'
-Warning	1292	Truncated incorrect DOUBLE value: 'w'
-Warning	1292	Truncated incorrect DOUBLE value: 'a'
-Warning	1292	Truncated incorrect DOUBLE value: 'e'
-Warning	1292	Truncated incorrect DOUBLE value: 'u'
+Warning	1292	Truncated incorrect DOUBLE value: 'r'
 Warning	1292	Truncated incorrect DOUBLE value: 's'
-Warning	1292	Truncated incorrect DOUBLE value: 'g'
-Warning	1292	Truncated incorrect DOUBLE value: 'b'
-Warning	1292	Truncated incorrect DOUBLE value: 'y'
-Warning	1292	Truncated incorrect DOUBLE value: 'p'
 Warning	1292	Truncated incorrect DOUBLE value: 't'
+Warning	1292	Truncated incorrect DOUBLE value: 'u'
+Warning	1292	Truncated incorrect DOUBLE value: 'v'
+Warning	1292	Truncated incorrect DOUBLE value: 'w'
 Warning	1292	Truncated incorrect DOUBLE value: 'x'
-Warning	1292	Truncated incorrect DOUBLE value: 'l'
-Warning	1292	Truncated incorrect DOUBLE value: 'k'
-Warning	1292	Truncated incorrect DOUBLE value: 'i'
+Warning	1292	Truncated incorrect DOUBLE value: 'y'
+Warning	1292	Truncated incorrect DOUBLE value: 'z'
 drop table t1,t2,t3,t4;
 set @@optimizer_switch= default;
 #launchpad BUG#609045

mysql-test/r/subselect_sj2_jcl6.result

@@ -1184,7 +1184,7 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	PRIMARY	t1	ref	PRIMARY	PRIMARY	5	const	1	Using where; Using index
 1	PRIMARY	t2	ALL	NULL	NULL	NULL	NULL	1	Start temporary; Using join buffer (flat, BNL join)
 1	PRIMARY	t3	ALL	NULL	NULL	NULL	NULL	2	Using where; Using join buffer (incremental, BNL join)
-1	PRIMARY	t4	hash_index	NULL	#hash#$hj:PRIMARY	54:59	test.t3.t3_c	2	Using where; End temporary; Using join buffer (incremental, BNLH join)
+1	PRIMARY	t4	hash_index	NULL	#hash#$hj:PRIMARY	54:59	test.t3.t3_c	2	Using where; Using index; End temporary; Using join buffer (incremental, BNLH join)
 DROP TABLE t1,t2,t3,t4;
 #
 # MDEV-6263: Wrong result when using IN subquery with order by

mysql-test/suite/vcol/r/vcol_select_myisam.result

@@ -295,3 +295,112 @@ Note	1003	select `test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a` from `test`.`t1`
 SELECT * FROM t1 NATURAL JOIN t2;
 b	a
 DROP TABLE t1,t2;
+create table t1 (
+pk integer auto_increment,
+bi integer not null,
+vi integer generated always as (bi) virtual,
+bc varchar(1) not null,
+vc varchar(2) generated always as (concat(bc, bc)),
+primary key (pk),
+key (vi, vc));
+insert t1 (bi, bc) values (0, 'x'), (0, 'n'), (1, 'w'), (7, 's'), (0, 'a'), (4, 'd'), (1, 'w'), (1, 'j'), (1, 'm'), (4, 'k'), (7, 't'), (4, 'k'), (2, 'e'), (0, 'i'), (1, 't'), (6, 'z'), (3, 'c'), (6, 'i'), (8, 'v');
+create table t2 (
+pk integer auto_increment,
+bi integer not null,
+vi integer generated always as (bi) virtual,
+bc varchar(257) not null,
+vc varchar(2) generated always as (concat(bc, bc)),
+primary key (pk),
+key (vi, vc));
+insert t2 (bi, bc) values (1, 'c'), (8, 'm'), (9, 'd'), (6, 'y'), (1, 't'), (6, 'd'), (2, 's'), (4, 'r'), (8, 'm'), (4, 'b'), (4, 'x'), (7, 'g'), (4, 'p'), (1, 'q'), (9, 'w'), (4, 'd'), (8, 'e'), (4, 'b'), (8, 'y');
+explain # should be using join buffer
+select t2.vi from (t2 as t3 right join (t2 left join t1 on (t1.bi = t2.vi)) on (t1.vc = t2.vc));
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	index	NULL	vi	10	NULL	19	Using index
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	19	Using where; Using join buffer (flat, BNL join)
+1	SIMPLE	t3	index	NULL	PRIMARY	4	NULL	19	Using where; Using index; Using join buffer (incremental, BNL join)
+select t2.vi from (t2 as t3 right join (t2 left join t1 on (t1.bi = t2.vi)) on (t1.vc = t2.vc));
+vi
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+1
+2
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+4
+6
+6
+6
+6
+7
+7
+8
+8
+8
+8
+9
+9
+drop table t2,t1;

mysql-test/suite/vcol/t/vcol_select_myisam.test

@@ -68,3 +68,31 @@ SELECT * FROM t1 NATURAL JOIN t2;
 SELECT * FROM t1 NATURAL JOIN t2;
 
 DROP TABLE t1,t2;
+
+#
+# MDEV-11640 gcol.gcol_select_myisam fails in buildbot on Power
+#
+
+create table t1 (
+  pk integer auto_increment,
+  bi integer not null,
+  vi integer generated always as (bi) virtual,
+  bc varchar(1) not null,
+  vc varchar(2) generated always as (concat(bc, bc)),
+  primary key (pk),
+  key (vi, vc));
+insert t1 (bi, bc) values (0, 'x'), (0, 'n'), (1, 'w'), (7, 's'), (0, 'a'), (4, 'd'), (1, 'w'), (1, 'j'), (1, 'm'), (4, 'k'), (7, 't'), (4, 'k'), (2, 'e'), (0, 'i'), (1, 't'), (6, 'z'), (3, 'c'), (6, 'i'), (8, 'v');
+create table t2 (
+  pk integer auto_increment,
+  bi integer not null,
+  vi integer generated always as (bi) virtual,
+  bc varchar(257) not null,
+  vc varchar(2) generated always as (concat(bc, bc)),
+  primary key (pk),
+  key (vi, vc));
+insert t2 (bi, bc) values (1, 'c'), (8, 'm'), (9, 'd'), (6, 'y'), (1, 't'), (6, 'd'), (2, 's'), (4, 'r'), (8, 'm'), (4, 'b'), (4, 'x'), (7, 'g'), (4, 'p'), (1, 'q'), (9, 'w'), (4, 'd'), (8, 'e'), (4, 'b'), (8, 'y');
+explain # should be using join buffer
+select t2.vi from (t2 as t3 right join (t2 left join t1 on (t1.bi = t2.vi)) on (t1.vc = t2.vc));
+--sorted_result
+select t2.vi from (t2 as t3 right join (t2 left join t1 on (t1.bi = t2.vi)) on (t1.vc = t2.vc));
+drop table t2,t1;

sql/sql_select.cc

@@ -1111,6 +1111,34 @@ int JOIN::optimize()
 }
 
 
+int JOIN::init_join_caches()
+{
+  JOIN_TAB *tab;
+
+  for (tab= first_linear_tab(this, WITH_BUSH_ROOTS, WITHOUT_CONST_TABLES);
+       tab;
+       tab= next_linear_tab(this, tab, WITH_BUSH_ROOTS))
+  {
+    TABLE *table= tab->table;
+    if (table->file->keyread_enabled())
+    {
+      if (!(table->file->index_flags(table->file->keyread, 0, 1) & HA_CLUSTERED_INDEX))
+        table->mark_columns_used_by_index(table->file->keyread, table->read_set);
+    }
+    else if ((tab->read_first_record == join_read_first ||
+              tab->read_first_record == join_read_last) &&
+             !tab->filesort && table->covering_keys.is_set(tab->index) &&
+             !table->no_keyread)
+    {
+      table->prepare_for_keyread(tab->index, table->read_set);
+    }
+    if (tab->cache && tab->cache->init(select_options & SELECT_DESCRIBE))
+      revise_cache_usage(tab);
+  }
+  return 0;
+}
+
+
 /**
   global select optimisation.
 
@@ -2122,6 +2150,9 @@ JOIN::optimize_inner()
   if (make_aggr_tables_info())
     DBUG_RETURN(1);
 
+  if (init_join_caches())
+    DBUG_RETURN(1);
+
   error= 0;
 
   if (select_options & SELECT_DESCRIBE)
@@ -10408,11 +10439,10 @@ void set_join_cache_denial(JOIN_TAB *join_tab)
     if (join_tab->cache->prev_cache)
       join_tab->cache->prev_cache->next_cache= 0;
     /*
-      No need to do the same for next_cache since cache denial is done
-      backwards starting from the latest cache in the linked list (see
-      revise_cache_usage()).
+      Same for the next_cache
     */
-    DBUG_ASSERT(!join_tab->cache->next_cache);
+    if (join_tab->cache->next_cache)
+      join_tab->cache->next_cache->prev_cache= 0;
 
     join_tab->cache->free();
     join_tab->cache= 0;
@@ -10872,8 +10902,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
   case JT_ALL:
     if (cache_level == 1)
       prev_cache= 0;
-    if ((tab->cache= new (root) JOIN_CACHE_BNL(join, tab, prev_cache)) &&
-         !tab->cache->init(options & SELECT_DESCRIBE))
+    if ((tab->cache= new (root) JOIN_CACHE_BNL(join, tab, prev_cache)))
     {
       tab->icp_other_tables_ok= FALSE;
       return (2 - MY_TEST(!prev_cache));
@@ -10907,8 +10936,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
         goto no_join_cache;
       if (cache_level == 3)
         prev_cache= 0;
-      if ((tab->cache= new (root) JOIN_CACHE_BNLH(join, tab, prev_cache)) &&
-          !tab->cache->init(options & SELECT_DESCRIBE))
+      if ((tab->cache= new (root) JOIN_CACHE_BNLH(join, tab, prev_cache)))
       {
         tab->icp_other_tables_ok= FALSE;        
         return (4 - MY_TEST(!prev_cache));
@@ -10928,8 +10956,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
       {
         if (cache_level == 5)
           prev_cache= 0;
-        if ((tab->cache= new (root) JOIN_CACHE_BKA(join, tab, flags, prev_cache)) &&
-            !tab->cache->init(options & SELECT_DESCRIBE))
+        if ((tab->cache= new (root) JOIN_CACHE_BKA(join, tab, flags, prev_cache)))
           return (6 - MY_TEST(!prev_cache));
         goto no_join_cache;
       }
@@ -10937,8 +10964,7 @@ uint check_join_cache_usage(JOIN_TAB *tab,
       {
         if (cache_level == 7)
           prev_cache= 0;
-        if ((tab->cache= new (root) JOIN_CACHE_BKAH(join, tab, flags, prev_cache)) &&
-            !tab->cache->init(options & SELECT_DESCRIBE))
+        if ((tab->cache= new (root) JOIN_CACHE_BKAH(join, tab, flags, prev_cache)))
 	{
           tab->idx_cond_fact_out= FALSE;
           return (8 - MY_TEST(!prev_cache));
@@ -19347,8 +19373,9 @@ join_read_first(JOIN_TAB *tab)
   TABLE *table=tab->table;
   DBUG_ENTER("join_read_first");
 
-  if (table->covering_keys.is_set(tab->index) && !table->no_keyread)
-    table->file->ha_start_keyread(tab->index);
+  DBUG_ASSERT(table->no_keyread ||
+              !table->covering_keys.is_set(tab->index) ||
+              table->file->keyread == tab->index);
   tab->table->status=0;
   tab->read_record.read_record=join_read_next;
   tab->read_record.table=table;
@@ -19386,8 +19413,9 @@ join_read_last(JOIN_TAB *tab)
   int error= 0;
   DBUG_ENTER("join_read_first");
 
-  if (table->covering_keys.is_set(tab->index) && !table->no_keyread)
-    table->file->ha_start_keyread(tab->index);
+  DBUG_ASSERT(table->no_keyread ||
+              !table->covering_keys.is_set(tab->index) ||
+              table->file->keyread == tab->index);
   tab->table->status=0;
   tab->read_record.read_record=join_read_prev;
   tab->read_record.table=table;

sql/sql_select.h

@@ -1512,6 +1512,7 @@ class JOIN :public Sql_alloc
   bool flatten_subqueries();
   bool optimize_unflattened_subqueries();
   bool optimize_constant_subqueries();
+  int init_join_caches();
   bool make_sum_func_list(List<Item> &all_fields, List<Item> &send_fields,
 			  bool before_group_by, bool recompute= FALSE);
 

sql/table.cc

@@ -6076,8 +6076,11 @@ MY_BITMAP *TABLE::prepare_for_keyread(uint index, MY_BITMAP *map)
   DBUG_ENTER("TABLE::prepare_for_keyread");
   if (!no_keyread)
     file->ha_start_keyread(index);
+  if (map != read_set || !(file->index_flags(index, 0, 1) & HA_CLUSTERED_INDEX))
+  {
     mark_columns_used_by_index(index, map);
     column_bitmaps_set(map);
+  }
   DBUG_RETURN(backup);
 }