create table L(A Int64) Engine=MergeTree order by A;
insert into L select number from numbers(3);

create table R(A Int64) Engine=MergeTree order by A;
insert into R select number from numbers(3000000);


select count() from L any left join R using A
--
3

Elapsed: 0.224 sec. Processed 3.00 million rows, 24.00 MB


select count() from L any left join (select * from R where A in (select A from L)) R1 using A;
--
3

Elapsed: 0.004 sec. Processed 8.20 thousand rows, 65.56 KB

Elapsed: 0.004 sec. Processed 8.20 thousand rows, 65.56 KB