1 files changed, 50 insertions, 0 deletions
diff --git a/mysql-test/t/join_cache.test b/mysql-test/t/join_cache.test
index f65f521f21a..a71db1081a1 100755
--- a/mysql-test/t/join_cache.test
+++ b/mysql-test/t/join_cache.test
@@ -2026,5 +2026,55 @@ SET join_cache_level=default;
 
 DROP TABLE t1,t2,t3,t4;
 
+--echo #
+--echo # BUG#52636: allowing JOINs on NULL values w/ join_cache_level = 5-8
+--echo #
+
+CREATE TABLE t1 (b int);
+INSERT INTO t1 VALUES (NULL),(3);
+
+CREATE TABLE t2 (a int, b int, KEY (b));
+INSERT INTO t2 VALUES (100,NULL),(150,200);
+
+set join_cache_level = 5;
+explain SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+--sorted_result
+SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+
+set join_cache_level = 8;
+explain SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+--sorted_result
+SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+
+# test crash when no key is worth collecting by BKA for t2's ref
+delete from t1;
+INSERT INTO t1 VALUES (NULL),(NULL);
+set join_cache_level = 5;
+explain SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+--sorted_result
+SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+
+DROP TABLE t1,t2;
+
+# test varchar keys
+CREATE TABLE t1 (b varchar(100));
+INSERT INTO t1 VALUES (NULL),("some varchar");
+
+CREATE TABLE t2 (a int, b varchar(100), KEY (b));
+INSERT INTO t2 VALUES (100,NULL),(150,"varchar"),(200,NULL),(250,"long long varchar");
+
+set join_cache_level = 5;
+explain SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+--sorted_result
+SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+
+set join_cache_level = 8;
+explain SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+--sorted_result
+SELECT t2.a FROM t1 LEFT JOIN t2 ON t2.b  = t1.b;
+
+set join_cache_level = default;
+DROP TABLE t1,t2;
+
 # this must be the last command in the file
 set @@optimizer_switch=@save_optimizer_switch;