Complex nested joins problems

I ran a randomized test for nested joins against PostgreSQL, Derby, and H2, and found some problems with Derby. The queries below throw NullPointerExceptions; the last query an assertion. The test case is here: http://code.google.com/p/h2database/source/browse/trunk/h2/src/test/org/h2/test/db/TestNestedJoins.java . There are probably shorter queries that are problematic, but I can't test it because Derby closes the connection after the assertion.

create table t0(x int);
create table t1(x int);
create table t2(x int);
create table t3(x int);
create table t4(x int);
insert into t4 values(0);
insert into t4 values(1);
insert into t4 values(2);
insert into t4 values(3);
create table t5(x int);
insert into t5 values(0);
insert into t5 values(1);
insert into t5 values(2);
insert into t5 values(3);
insert into t5 values(4);
create table t6(x int);
insert into t6 values(0);
insert into t6 values(1);
insert into t6 values(2);
insert into t6 values(3);
insert into t6 values(4);
insert into t6 values(5);
create table t7(x int);
insert into t7 values(0);
insert into t7 values(1);
insert into t7 values(2);
insert into t7 values(3);
insert into t7 values(4);
insert into t7 values(5);
insert into t7 values(6);
create table t8(x int);
insert into t8 values(0);
insert into t8 values(1);
insert into t8 values(2);
insert into t8 values(3);
insert into t8 values(4);
insert into t8 values(5);
insert into t8 values(6);
insert into t8 values(7);
create table t9(x int);
insert into t9 values(0);
insert into t9 values(1);
insert into t9 values(2);
insert into t9 values(3);
insert into t9 values(4);
insert into t9 values(5);
insert into t9 values(6);
insert into t9 values(7);
insert into t9 values(8);
insert into t0 values(1);
insert into t1 values(2);
insert into t0 values(3);
insert into t1 values(3);
insert into t2 values(4);
insert into t0 values(5);
insert into t2 values(5);
insert into t1 values(6);
insert into t2 values(6);
insert into t0 values(7);
insert into t1 values(7);
insert into t2 values(7);
insert into t3 values(8);
insert into t0 values(9);
insert into t3 values(9);
insert into t1 values(10);
insert into t3 values(10);
insert into t0 values(11);
insert into t1 values(11);
insert into t3 values(11);
insert into t2 values(12);
insert into t3 values(12);
insert into t0 values(13);
insert into t2 values(13);
insert into t3 values(13);
insert into t1 values(14);
insert into t2 values(14);
insert into t3 values(14);
insert into t0 values(15);
insert into t1 values(15);
insert into t2 values(15);
insert into t3 values(15);
select t0.x , t1.x , t2.x , t3.x , t4.x , t5.x , t6.x , t7.x , t8.x from (((t0 inner join ((t1 right outer join (t2 inner join t3 on t2.x = t3.x ) on t1.x = t2.x ) left outer join (t4 inner join t5 on t4.x = t5.x ) on t1.x = t4.x ) on t0.x = t2.x ) left outer join (t6 inner join t7 on t6.x = t7.x ) on t1.x = t6.x ) inner join t8 on t5.x = t8.x );
select t0.x , t1.x , t2.x , t3.x , t4.x , t5.x , t6.x , t7.x from ((t0 right outer join t1 on t0.x = t1.x ) inner join (((t2 inner join (t3 left outer join t4 on t3.x = t4.x ) on t2.x = t3.x ) right outer join t5 on t2.x = t5.x ) left outer join (t6 inner join t7 on t6.x = t7.x ) on t4.x = t6.x ) on t0.x = t5.x );
select t0.x , t1.x , t2.x , t3.x , t4.x , t5.x , t6.x , t7.x from ((((t0 left outer join t1 on t0.x = t1.x ) right outer join t2 on t0.x = t2.x ) right outer join t3 on t0.x = t3.x ) inner join ((t4 inner join t5 on t4.x = t5.x ) right outer join (t6 right outer join t7 on t6.x = t7.x ) on t4.x = t6.x ) on t1.x = t4.x );
select t0.x , t1.x , t2.x , t3.x , t4.x , t5.x from (((t0 inner join t1 on t0.x = t1.x ) right outer join (t2 right outer join t3 on t2.x = t3.x ) on t0.x = t2.x ) inner join (t4 left outer join t5 on t4.x = t5.x ) on t1.x = t4.x );
select t0.x , t1.x , t2.x , t3.x , t4.x , t5.x , t6.x from ((t0 right outer join (t1 right outer join (t2 left outer join (t3 left outer join t4 on t3.x = t4.x ) on t2.x = t3.x ) on t1.x = t3.x ) on t0.x = t1.x ) left outer join (t5 inner join t6 on t5.x = t6.x ) on t2.x = t5.x );