Postgres with clause to substring large char column into rows - postgresql

Question

Issue: I have limitations in the code that I am writing that won't read in columns > 4K bytes
Want: Turn a single row into multiple rows with a new max length and have the ordinal to keep them in order.
I have done this activity in DB2 previously using the with clause and a recursive query, I am trying to convert the code to work with Postgres. I don't have as much Postgres experience to know if there is a better way to do this.
To start I have a table
Create table test_long_text (
test_id numeric(12,0) NOT NULL,
long_text varchar(64000)
)
Here is the query I have been trying to write and failed.
WITH RECURSIVE rec(test_id, len, ord, pos) as (
select test_id, octet_length(long_text), 1, 1 from test_long_text
union all
select test_id, len, ord+1, pos+4096 from rec where len >=4096)
select A.test_id, ord, substr(long_text, pos, 4096) from test_long_text A
inner join rec using (test_id)
order by A.test_id, ord
Currently, I get an error negative substring length not allowed or it hangs indefinitely.
Expected Results: Where the text is chunks of text at a max of 4096 bytes long. pretend ABC is a longer string.
+--------------+
| ID |ORD|TEXT |
| 1 |1 |ABC |
+--------------+
| 2 |1 |ABC |
+--------------+
| 2 |2 |DEF |
+--------------+
| 3 |1 |ABC |
+--------------+
| 3 |2 |DEF |
+--------------+
| 3 |3 |GHI |
+--------------+

Answer 1

This example shows how to split values of text column into 3-characters parts:
with t(x) as (values('1234567890abcdef'::text), ('qwertyuiop'))
select *, substring(x, f.p, 3)
from t, generate_series(1, length(x), 3) with ordinality as f(p, i);
┌──────────────────┬────┬───┬───────────┐
│ x │ p │ i │ substring │
├──────────────────┼────┼───┼───────────┤
│ 1234567890abcdef │ 1 │ 1 │ 123 │
│ 1234567890abcdef │ 4 │ 2 │ 456 │
│ 1234567890abcdef │ 7 │ 3 │ 789 │
│ 1234567890abcdef │ 10 │ 4 │ 0ab │
│ 1234567890abcdef │ 13 │ 5 │ cde │
│ 1234567890abcdef │ 16 │ 6 │ f │
│ qwertyuiop │ 1 │ 1 │ qwe │
│ qwertyuiop │ 4 │ 2 │ rty │
│ qwertyuiop │ 7 │ 3 │ uio │
│ qwertyuiop │ 10 │ 4 │ p │
└──────────────────┴────┴───┴───────────┘
You can simply adapt it to your data.