column size too large, is this a bug?

I have a query which get's data from a single table.
When I try to get data from for an RFQ which has around 5000 rows, it
is breaking off at 18th row.
If i reduce some columns , then it returns all the rows and not so slow.
I have tried with different sets of column and there is no pattern
based on columns.

But one thing is sure one size of the rows grows more than some bytes,
the records do not get returned. Now the following query returns me all
5001 rows to me pretty fast

select
_level_ as l,
nextval('seq_pk_bom_detail') as bom_detail,
prior nextval('seq_pk_bom_detail') as parent_subassembly,
parent_part_number,
customer_part_number,
/* mfr_name,
mfr_part,
description,*/
commodity,
needs_date,
target_price,
comments,
case qty_per
when null then 0.00001
when 0 then 0.00001
else qty_per
end,
qty_multiplier1,
qty_multiplier2,
qty_multiplier3,
qty_multiplier4,
qty_multiplier5
from bom_detail_work_clean
where (0=0)
and bom_header=20252
and file_number = 1
start with customer_part_number = 'Top Assembly 1'
connect by parent_part_number = prior customer_part_number;

But if I uncomment the description then it returns me only 18 rows.

select
_level_ as l,
nextval('seq_pk_bom_detail') as bom_detail,
prior nextval('seq_pk_bom_detail') as parent_subassembly,
parent_part_number,
customer_part_number,
/* mfr_name,
mfr_part,*/
description,
commodity,
needs_date,
target_price,
comments,
case qty_per
when null then 0.00001
when 0 then 0.00001
else qty_per
end,
qty_multiplier1,
qty_multiplier2,
qty_multiplier3,
qty_multiplier4,
qty_multiplier5
from bom_detail_work_clean
where (0=0)
and bom_header=20252
and file_number = 1
start with customer_part_number = 'Top Assembly 1'
connect by parent_part_number = prior customer_part_number;

Now these 18 rows are level 2 records in heirarchical query. I have a
feeling the server has some memory paging mechanism
and if it can not handle beyond certain byets, it just returns what it
has.
During your investigation of optimization of postgreSQL did you come
across any setting that might help us ?

Thanks!

Qing

PS: I just reload the file while reducing the content in the
description column.
The file got uploaded. So looks like the problem is size of the record
being inserted.