Fixed MDEV-13994 Bad join results with orderby_uses_equalities=on.

This patch effectively blocks the optimization that uses multiple
equalities for ORDER BY to remove tmp table in the case when
the first table happens to be the result of materialization of
a semi-join nest. Currently there is no code at the execution level
that would support the optimization in this case.

1 files changed, 43 insertions, 0 deletions

diff --git a/mysql-test/t/order_by.test b/mysql-test/t/order_by.test
index 8722401ccae..914911648b2 100644
--- a/mysql-test/t/order_by.test
+++ b/mysql-test/t/order_by.test
@@ -2106,3 +2106,46 @@ INSERT INTO t1 VALUES (1),(2),(3);
 SELECT DISTINCT pk FROM t1 GROUP BY 'foo';
 SELECT DISTINCT pk FROM t1;
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-13994: Bad join results with orderby_uses_equalities=on
+--echo #
+
+CREATE TABLE books (
+  id int(16) NOT NULL AUTO_INCREMENT,
+  library_id int(16) NOT NULL DEFAULT 0,
+  wings_id int(12) NOT NULL DEFAULT 0,
+  scheduled_for_removal int(1) DEFAULT 0,
+  PRIMARY KEY (id),
+  KEY library_idx (library_id)
+) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
+
+INSERT INTO books VALUES (32625,8663,707,0),(32624,8663,505,1);
+
+CREATE TABLE wings (
+  id int(11) NOT NULL AUTO_INCREMENT,
+  department_id int(11) DEFAULT NULL,
+  PRIMARY KEY (id)
+) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
+
+INSERT INTO wings VALUES (505,11745),(707,11768);
+
+let $q=
+SELECT wings.id as wing_id, wings.department_id FROM wings
+  WHERE wings.id IN ( SELECT books.wings_id FROM books
+                        WHERE books.library_id = 8663 AND
+                              books.scheduled_for_removal=0 )
+ORDER BY wings.id;
+
+SET @save_optimizer_switch=@@optimizer_switch;
+
+SET optimizer_switch='orderby_uses_equalities=off';
+eval $q;
+
+SET optimizer_switch='orderby_uses_equalities=on';
+eval $q;
+eval explain extended $q;
+
+set optimizer_switch= @save_optimizer_switch;
+
+DROP TABLE books, wings;