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.

2 files changed, 137 insertions, 0 deletions

diff --git a/mysql-test/suite/vcol/r/vcol_select_myisam.result b/mysql-test/suite/vcol/r/vcol_select_myisam.result
index 30d21d6792a..88a9e608c9d 100644
--- a/mysql-test/suite/vcol/r/vcol_select_myisam.result
+++ b/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
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+4
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+9
+drop table t2,t1;
diff --git a/mysql-test/suite/vcol/t/vcol_select_myisam.test b/mysql-test/suite/vcol/t/vcol_select_myisam.test
index c86ae10a4b3..5dd08894fea 100644
--- a/mysql-test/suite/vcol/t/vcol_select_myisam.test
+++ b/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;