通常の再帰 CTE ではこれを行うことはできません。階層の奥深くに json 値を設定することはほとんど不可能だからです。しかし、それを逆にすることもできます: 葉から始まり、根までツリーを構築します:
-- calculate node levels
WITH RECURSIVE c AS (
SELECT *, 0 as lvl
FROM customer_area_node
-- use parameters here, to select the root first
WHERE customer_id = 2 AND parent_id IS NULL
UNION ALL
SELECT customer_area_node.*, c.lvl + 1 as lvl
FROM customer_area_node
JOIN c ON customer_area_node.parent_id = c.id
),
-- select max level
maxlvl AS (
SELECT max(lvl) maxlvl FROM c
),
-- accumulate children
j AS (
SELECT c.*, json '[]' children -- at max level, there are only leaves
FROM c, maxlvl
WHERE lvl = maxlvl
UNION ALL
-- a little hack, because PostgreSQL doesn't like aggregated recursive terms
SELECT (c).*, array_to_json(array_agg(j)) children
FROM (
SELECT c, j
FROM j
JOIN c ON j.parent_id = c.id
) v
GROUP BY v.c
)
-- select only root
SELECT row_to_json(j) json_tree
FROM j
WHERE lvl = 0;
そして、これはPostgreSQL 9.2+でも機能します
SQLフィドル
更新:不正なリーフノードも処理する必要があるバリアント (レベルが 1 からmax-level にある):
WITH RECURSIVE c AS (
SELECT *, 0 as lvl
FROM customer_area_node
WHERE customer_id = 1 AND parent_id IS NULL
UNION ALL
SELECT customer_area_node.*, c.lvl + 1
FROM customer_area_node
JOIN c ON customer_area_node.parent_id = c.id
),
maxlvl AS (
SELECT max(lvl) maxlvl FROM c
),
j AS (
SELECT c.*, json '[]' children
FROM c, maxlvl
WHERE lvl = maxlvl
UNION ALL
SELECT (c).*, array_to_json(array_agg(j) || array(SELECT r
FROM (SELECT l.*, json '[]' children
FROM c l, maxlvl
WHERE l.parent_id = (c).id
AND l.lvl < maxlvl
AND NOT EXISTS (SELECT 1
FROM c lp
WHERE lp.parent_id = l.id)) r)) children
FROM (SELECT c, j
FROM c
JOIN j ON j.parent_id = c.id) v
GROUP BY v.c
)
SELECT row_to_json(j) json_tree
FROM j
WHERE lvl = 0;
これは PostgreSQL 9.2 以降でも動作するはずですが、テストできません。(現在、9.5+ でしかテストできません)。
これらのソリューションは、任意の階層テーブル内の任意の列を処理できますが、常にint型指定されたlvlJSON プロパティを出力に追加します。
http://rextester.com/YNU7932