Alternative solutions to an array search in PostgreSQL - arrays

Question

I am not sure if my database design is good for this tricky case and I also ask for help how the query for this could look like.
I plan a query with the following table:
search_array | value | id
-----------------------+-------+----
{XYa,YZb,WQb} | b | 1
{XYa,YZb,WQb,RSc,QZa} | a | 2
{XYc,YZa} | c | 3
{XYb} | a | 4
{RSa} | c | 5
There are 5 main elements in the search_array: XY, YZ, WQ, RS, QZ and 3 Values: a, b, c that are concardinated to each element.
Each row has also one value: a, b or c.
My aim is to find all rows that fit to a specific row in this sense: At first it should be checked if they have any same main elements in their search_arrays (yellow marked in the example).
As example:
Row id 4 an row id 5 wouldnt match because XY != RS.
Row id 1, 2 and 3 would match two times because they have all XY and YZ.
Row id 1 and 2 would even match three times because they have also WQ in common.
And second: if there is a Main Element match it should be 'crosschecked' if the lowercase letters after the Main Elements fit to the value of the other row.
As example: The only match for Row id 1 in the table would be Row id 4 because they both search for XY and the low letters after the elements match each value of the two rows.
Another match would be ROW id 2 and 5 with RS and search c to value c and search a to value a (green and orange marked).
My idea was to cut the search_array elements in the query in two parts with the RIGHT and LEFT command for strings. But I dont know how to combine the subqueries for this search.
Or would be a complete other solution faster? Like splitting the search array into another table with the columns 'foregin key' to the maintable, 'main element' and 'searched_value'. I am not sure if this is the best solution because the program would all the time switch to the main table to find two rows out of 3 million rows to compare their searched_values to the values?
Thank you very much for your answers and your time!

Answer 1

You'll have to represent the data in a normalized fashion. I'll do it in a WITH clause, but it would be better to store the data in this fashion to begin with.
WITH unravel AS (
SELECT t.id, t.value,
substr(u.val, 1, 2) AS arr_main,
substr(u.val, 3, 1) AS arr_val
FROM mytable AS t
CROSS JOIN LATERAL unnest(t.search_array) AS u(val)
)
SELECT a.id AS first_id,
a.value AS first_value,
b.id AS second_id,
b.value AS second_value,
a.arr_main AS main_element
FROM unravel AS a
JOIN unravel AS b
ON a.arr_main = b.arr_main
AND a.arr_val = b.value
AND b.arr_val = a.value;