Exponential optimization time for conditions on columns of nested merged derived tables/views

create table t1 (f1 int, f2 int, f3 int, f4 int, f5 int);

insert into t1 values (1,2,3,4,5),(5,4,3,2,1),(3,3,3,3,3);

--disable_query_log

let $levels= 20;

let $q= select f1 as a, f1 or f2 as s1 from t1;

let $i= 1;

while ($i < $levels)

{

  let $j= $i;

  inc $j;

  let $q= select a, s$i or s$i or s$i as s$j from ($q) dt$i;

  inc $i;

}

let $s= s$levels;

--echo # fast

eval select count(*) from ($q) x;

--echo # each of these never finishes

eval select count(*) from ($q) x where $s > 0;

eval select count(*) from ($q) x join t1 on x.$s = t1.f3;

eval select count(*) from t1 left join ($q) x on x.$s = t1.f3;

eval select count(*) from t1 where f1 in (select $s from ($q) x);

eval select count(*) from t1 where exists (select 1 from ($q) x where x.$s = t1.f1);

eval delete t1 from t1, ($q) x where t1.f1 = x.a and x.$s < -1000000;

--enable_query_log

drop table t1;

create table t1 (f1 int, f2 int, f3 int, f4 int, f5 int);

insert into t1 values (1,2,3,4,5),(5,4,3,2,1),(3,3,3,3,3);

-- never finishes; without "where s20 > 0" it takes 0.1 s

select count(*) from (select a, s19 or s19 or s19 as s20 from (select a, s18 or s18 or s18 as s19 from (select a, s17 or s17 or s17 as s18 from (select a, s16 or s16 or s16 as s17 from (select a, s15 or s15 or s15 as s16 from (select a, s14 or s14 or s14 as s15 from (select a, s13 or s13 or s13 as s14 from (select a, s12 or s12 or s12 as s13 from (select a, s11 or s11 or s11 as s12 from (select a, s10 or s10 or s10 as s11 from (select a, s9 or s9 or s9 as s10 from (select a, s8 or s8 or s8 as s9 from (select a, s7 or s7 or s7 as s8 from (select a, s6 or s6 or s6 as s7 from (select a, s5 or s5 or s5 as s6 from (select a, s4 or s4 or s4 as s5 from (select a, s3 or s3 or s3 as s4 from (select a, s2 or s2 or s2 as s3 from (select a, s1 or s1 or s1 as s2 from (select f1 as a, f1 or f2 as s1 from t1) dt1) dt2) dt3) dt4) dt5) dt6) dt7) dt8) dt9) dt10) dt11) dt12) dt13) dt14) dt15) dt16) dt17) dt18) dt19) x where s20 > 0;