MDEV-14241: Server crash in key_copy / get_matching_chain_by_join_key or valgrind warnings

In this case we were using the optimization derived_with_keys but we could not create a key
because the length of the key was greater than the max allowed(MI_MAX_KEY_LENGTH).
To do the join we needed to create a hash join key instead, but in the explain output it
showed that we were still referring to derived keys which were created but not used.

mysql-test/r/derived.result

@@ -1011,4 +1011,29 @@ id	id	data
 2	2	yes
 1	NULL	NULL
 drop table t1;
+#
+# MDEV-14241: Server crash in key_copy / get_matching_chain_by_join_key
+# or valgrind warnings
+#
+CREATE TABLE t1 (a VARCHAR(10)) ENGINE=MyISAM;
+CREATE OR REPLACE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
+INSERT INTO t1 VALUES ('foo'),('bar');
+CREATE TABLE t2 (b integer auto_increment primary key) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (NULL),(NULL);
+CREATE TABLE t3 (c VARCHAR(1024) CHARACTER SET utf8, d INT) ENGINE=MyISAM;
+CREATE OR REPLACE ALGORITHM=TEMPTABLE VIEW v3 AS SELECT * FROM t3;
+INSERT INTO t3 VALUES ('abc',NULL),('def',4);
+SET join_cache_level= 8;
+explain
+SELECT * FROM v1, t2, v3 WHERE a = c AND b = d;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	<derived2>	ALL	NULL	NULL	NULL	NULL	2	
+1	PRIMARY	<derived3>	hash_ALL	NULL	#hash#$hj	3075	func	2	Using where; Using join buffer (flat, BNLH join)
+1	PRIMARY	t2	eq_ref	PRIMARY	PRIMARY	4	v3.d	1	Using index
+3	DERIVED	t3	ALL	NULL	NULL	NULL	NULL	2	
+2	DERIVED	t1	ALL	NULL	NULL	NULL	NULL	2	
+SELECT * FROM v1, t2, v3 WHERE a = c AND b = d;
+a	b	c	d
+DROP VIEW v1, v3;
+DROP TABLE t1, t2, t3;
 # end of 5.5

mysql-test/t/derived.test

@@ -864,5 +864,28 @@ select distinct t1.id, tt.id, tt.data
 
 drop table t1;
 
+--echo #
+--echo # MDEV-14241: Server crash in key_copy / get_matching_chain_by_join_key
+--echo # or valgrind warnings
+--echo #
+
+CREATE TABLE t1 (a VARCHAR(10)) ENGINE=MyISAM;
+CREATE OR REPLACE ALGORITHM=TEMPTABLE VIEW v1 AS SELECT * FROM t1;
+INSERT INTO t1 VALUES ('foo'),('bar');
+
+CREATE TABLE t2 (b integer auto_increment primary key) ENGINE=MyISAM;
+INSERT INTO t2 VALUES (NULL),(NULL);
+
+CREATE TABLE t3 (c VARCHAR(1024) CHARACTER SET utf8, d INT) ENGINE=MyISAM;
+CREATE OR REPLACE ALGORITHM=TEMPTABLE VIEW v3 AS SELECT * FROM t3;
+INSERT INTO t3 VALUES ('abc',NULL),('def',4);
+
+SET join_cache_level= 8;
+explain
+SELECT * FROM v1, t2, v3 WHERE a = c AND b = d;
+SELECT * FROM v1, t2, v3 WHERE a = c AND b = d;
+
+DROP VIEW v1, v3;
+DROP TABLE t1, t2, t3;
 
 --echo # end of 5.5

sql/sql_select.cc

@@ -9513,7 +9513,7 @@ void JOIN::drop_unused_derived_keys()
       table->use_index(tab->ref.key);
     if (table->s->keys)
     {
-      if (tab->ref.key >= 0)
+      if (tab->ref.key >= 0 && tab->ref.key < MAX_KEY)
         tab->ref.key= 0;
       else
         table->s->keys= 0;