Store multidimensional array in database: relational or multidimensional?

Question

I have read numerous posts along the lines of multidimensional to single dimension, multidimensional database, and so on, but none of the answers helped. I did

Answer 1

This approach does not depend on the existence of a path or parent column. It is relational not recursive.

Since the table is static create a materialized view containing just the leaves to make searching faster:

create materialized view leave as
select cell
from (
    select cell,
        lag(cell,1,cell) over (order by cell desc) not like cell || '%' as leave
    from t
) s
where leave;

table leave;
 cell 
------
 CCCE
 CCCA
 CCBE
 CCBC
 BEDA
 BDDA
 BDCE
 BDCB
 BAA
 AEEB
 AEA
 AB
 AAC
 AAA

A materialized view is computed once at creation not at each query like a plain view. Create an index to speed it up:

create index cell_index on leave(cell);

If eventually the source table is altered just refresh the view:

refresh materialized view leave;

The search function receives text and returns a text array:

create or replace function get_descendants(c text)
returns text[] as $$
    select array_agg(distinct l order by l)
    from (
        select left(cell, generate_series(length(c), length(cell))) as l
        from leave
        where cell like c || '%'
    ) s;
$$ language sql immutable strict;

Pass the desired match to the function:

select get_descendants('A');
          get_descendants          
-----------------------------------
 {A,AA,AAA,AAC,AB,AE,AEA,AEE,AEEB}

select get_descendants('AEE');
 get_descendants 
-----------------
 {AEE,AEEB}

Test data:

create table t (cell text);
insert into t (cell) values
('A'),
('AA'),
('AAA'),
('AAC'),
('AB'),
('AE'),
('AEA'),
('AEE'),
('AEEB'),
('B'),
('BA'),
('BAA'),
('BD'),
('BDC'),
('BDCB'),
('BDCE'),
('BDD'),
('BDDA'),
('BE'),
('BED'),
('BEDA'),
('C'),
('CC'),
('CCB'),
('CCBC'),
('CCBE'),
('CCC'),
('CCCA'),
('CCCE'),
('CE');