Postgresql node traversal using Recursive CTE - postgresql

Question

I am just trying to learn graph traversal using Recursive CTE in postgresql.
Below is my data set:
i am using the below code to get the path along with existing columns(node & edges).
It is giving me output but path column is not in ARRAY format.
;WITH RECURSIVE CTE AS
(
SELECT NODE,EDGES,ARRAY[G.NODE]::TEXT AS PATH,1 AS LEVEL
FROM property_graph G
UNION ALL
SELECT G.NODE,G.EDGES,C.PATH || G.NODE,LEVEL + 1
FROM property_graph G
INNER JOIN CTE C ON G.NODE = ANY(C.EDGES)
WHERE G.NODE <> ALL(STRING_TO_ARRAY(C.PATH,'')) --Cond added to avoid cyclic graph
)
SELECT NODE,EDGES,PATH,LEVEL
FROM CTE
ORDER BY NODE,LEVEL;
Output:
Could you guys help me?
Thanks in advance.

Answer 1

The problem is that your PATH column is of type TEXT, and so is NODE, therefore the || operator performs string concatenation rather than array concatenation.
You should change the type of your PATH column from TEXT to TEXT[] (and then you can remove the STRING_TO_ARRAY in the WHERE clause.
For example:
WITH RECURSIVE CTE AS
(
SELECT NODE,EDGES,ARRAY[G.NODE]::TEXT[] AS PATH,1 AS LEVEL
FROM property_graph G
UNION ALL
SELECT G.NODE,G.EDGES,C.PATH || ARRAY[G.NODE]::TEXT[],LEVEL + 1
FROM property_graph G
INNER JOIN CTE C ON G.NODE = ANY(C.EDGES)
WHERE G.NODE <> ALL(C.PATH) --Cond added to avoid cyclic graph
)
SELECT NODE,EDGES,PATH,LEVEL
FROM CTE
ORDER BY NODE,LEVEL;