MWL#90: address review feedback: more test coverage

- Forgot to add .result file

mysql-test/r/subselect_mat.result

@@ -1286,6 +1286,38 @@ a	a in (select a from t1)
 2	0
 drop table t0, t1;
 set optimizer_switch='firstmatch=on';
+#
+# MWL#90, review feedback: check what happens when the subquery
+#   looks like candidate for MWL#90 checking at the first glance
+#   but then subselect_hash_sj_engine::init_permanent() discovers
+#   that it's not possible to perform duplicate removal for the 
+#   selected datatypes, and so materialization isn't applicable after
+#   all.
+#
+set @blob_len = 1024;
+set @suffix_len = @blob_len - @prefix_len;
+create table t1_1024 (a1 blob(1024), a2 blob(1024));
+create table t2_1024 (b1 blob(1024), b2 blob(1024));
+insert into t1_1024 values
+(concat('1 - 00', repeat('x', @suffix_len)), concat('2 - 00', repeat('x', @suffix_len)));
+insert into t1_1024 values
+(concat('1 - 01', repeat('x', @suffix_len)), concat('2 - 01', repeat('x', @suffix_len)));
+insert into t1_1024 values
+(concat('1 - 02', repeat('x', @suffix_len)), concat('2 - 02', repeat('x', @suffix_len)));
+insert into t2_1024 values
+(concat('1 - 01', repeat('x', @suffix_len)), concat('2 - 01', repeat('x', @suffix_len)));
+insert into t2_1024 values
+(concat('1 - 02', repeat('x', @suffix_len)), concat('2 - 02', repeat('x', @suffix_len)));
+insert into t2_1024 values
+(concat('1 - 03', repeat('x', @suffix_len)), concat('2 - 03', repeat('x', @suffix_len)));
+explain select left(a1,7), left(a2,7) from t1_1024 where (a1,3) in (select substring(b1,1,1024), count(*) from t2_1024 where b1 > '0');
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t1_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+2	DEPENDENT SUBQUERY	t2_1024	ALL	NULL	NULL	NULL	NULL	3	Using where
+select left(a1,7), left(a2,7) from t1_1024 where (a1,3) in (select substring(b1,1,1024), count(*) from t2_1024 where b1 > '0');
+left(a1,7)	left(a2,7)
+1 - 01x	2 - 01x
+drop table t1_1024, t2_1024;
 set @@optimizer_switch=default;
 create table t0 (a int);
 insert into t0 values (0),(1),(2);