PostgreSQL - Recursive query with a where clause - postgresql

Question

In PostgreSQL, how to execute a recursive query with "dynamics" clauses ?
I'm using a recursive query because my data is a hierarchical model. An object can have children, themselves can also have children...
.
My goal is to find the last children of a searched object. My recursive query use a specific value in the where clause (A in this exemple, the searched object). This values are stored in an other table (called my_table here). An other table store every relations between object (A to B, A to C, A to D, D to E, D to F...), called my_table_filiation here. I need to repeat all this recursive query for each distinct values of my_table.cadastral_reference (A, B, C, D, E, F).
In other words how can I dynamically change a clause in a recursive query and run it for every values of a distinct table ?
Tables are like this :
CREATE TABLE IF NOT EXISTS my_table
(
id integer NOT NULL DEFAULT nextval('my_table_id_seq'::regclass),
cadastral_reference character varying(14) COLLATE pg_catalog."default",
filiation character varying COLLATE pg_catalog."default",
CONSTRAINT my_table_pkey PRIMARY KEY (id)
)
CREATE TABLE IF NOT EXISTS my_table_filiation
(
id integer NOT NULL DEFAULT nextval('my_table_filiation_id_seq'::regclass),
mother character varying(14) COLLATE pg_catalog."default",
daughter character varying(14) COLLATE pg_catalog."default",
CONSTRAINT my_table_filiation_pkey PRIMARY KEY (id)
)
Recursive query is like this :
WITH RECURSIVE q_filiation (mother, daughter) AS (
SELECT mother, daughter
FROM my_table_filiation
WHERE mother = 'A'
UNION ALL
SELECT p.mother, p.daughter
FROM q_filiation f, my_table_filiation p
WHERE p.mother = f.daughter
)
SELECT
array_agg(DISTINCT mother) AS mother,
array_agg(daughter) AS last_daughter,
FROM q_filiation
Actual result :
mother | last_daughter
--------------------
{A} | {E,F}
Desired results (the where clause declined with every values of my_table.cadastral_reference):
mother | last_daughter
--------------------
{A} | {E,F}
{B} | {}
{C} | {}
{D} | {E,F}

Answer 1

Finally I create a function with my previous query :
CREATE OR REPLACE FUNCTION my_function_filiation(
research_filiation character varying,
OUT mother character varying,
OUT daughter character varying)
RETURNS SETOF record
LANGUAGE 'plpgsql'
COST 100
VOLATILE PARALLEL UNSAFE
ROWS 1000
AS $BODY$
DECLARE
rec record;
sql text;
BEGIN
sql := '
WITH RECURSIVE q_filiation (mother, daughter) AS (
SELECT mother, daughter
FROM my_table_filiation
WHERE mother = '''||research_filiation||'''
UNION ALL
SELECT p.mother, p.daughter
FROM q_filiation f, my_table_filiation p
WHERE p.mother = f.daughter
)
SELECT
array_agg(DISTINCT mother) AS mother,
array_agg(daughter) AS last_daughter,
FROM q_filiation
';
FOR rec IN EXECUTE sql
LOOP
mother := rec.mother;
daughter := rec.daughter;
RETURN NEXT;
END LOOP;
END;
$BODY$;
Now I can use it in queries :
SELECT
my_function_filiation(p.cadastral_reference)
FROM my_table p;
If anyone know better solutions, on method or syntax, feel free to contribute.