我最终创建了三个函数。可能做得更少，但这些函数可以在其他查询中重用。基本上，JSON 输出中应该有一个值数组的任何位置都由一个函数处理，该函数返回一个被json_agg()'ed 的记录集。
CREATE OR REPLACE FUNCTION get_measures_by_inventory_as_json(invid UUID, del TIMESTAMP WITH TIME ZONE DEFAULT now())
RETURNS TABLE(inventory_id UUID, measure_json JSON)
AS $$
-- returns a JSONified record per measure tied to an inventory record
SELECT m.inventory_id, json_build_object(
'id', m.id,
'quantity', m.quantity,
'read', TRUNC(EXTRACT(EPOCH FROM m.read_date)),
'created', TRUNC(EXTRACT(EPOCH FROM m.created)),
'updated', TRUNC(EXTRACT(EPOCH FROM m.updated)),
'deleted', TRUNC(EXTRACT(EPOCH FROM m.deleted))
)
FROM measure m
WHERE m.inventory_id = invid
AND (m.deleted >= del);
$$
LANGUAGE sql;
CREATE OR REPLACE FUNCTION get_inventories_by_location_as_json(locid UUID, del TIMESTAMP WITH TIME ZONE DEFAULT now())
RETURNS TABLE(location_id UUID, inventory_json JSON)
AS $$
-- returns a JSONified set of inventory items, with product info and measures, given a location
SELECT i.location_id, json_build_object(
'id', i.id,
'product_id', p.id,
'name', p.name,
'mass_quantity', p.mass_quantity,
'mass_unit', um.code,
'count_unit', uc.code,
'thumb', p.product_picture_uri,
'sort_order', i.sort_order,
'par_level', i.par_level,
'created', TRUNC(EXTRACT(EPOCH FROM i.created)),
'updated', TRUNC(EXTRACT(EPOCH FROM i.updated)),
'deleted', TRUNC(EXTRACT(EPOCH FROM i.deleted)),
'measures', COALESCE((SELECT json_agg(measure_json) FROM get_measures_by_inventory_as_json(i.id)), '[]')::json
)
FROM inventory i
INNER JOIN product p ON i.product_id = p.id
LEFT JOIN unit um ON p.mass_unit_id = um.id
LEFT JOIN unit uc ON p.count_unit_id = uc.id
WHERE i.location_id = locid
AND i.deleted >= del
AND p.deleted >= del;
$$
LANGUAGE sql;
CREATE OR REPLACE FUNCTION get_inventories_recursive_as_json(locid UUID[], del TIMESTAMP WITH TIME ZONE DEFAULT now())
RETURNS JSON
AS $$
-- returns JSONified location info and inventories in that location
-- and recurses into child locations, showing the same
SELECT json_agg(loc) FROM (
SELECT l.id, array_agg(c.id), json_build_object(
'id', l.id,
'name', l.name,
'type', t.code,
'locations', get_inventories_recursive_as_json(array_agg(c.id)),
'inventories', COALESCE((SELECT json_agg(inventory_json) FROM get_inventories_by_location_as_json(l.id)),'[]')::json
) AS loc
FROM location l
LEFT OUTER JOIN location c ON l.id = c.parent_id
INNER JOIN location_type t ON l.location_type_id = t.id
WHERE l.id = ANY(locid)
AND l.deleted >= del
GROUP BY l.id, l.name, t.code
) AS out;
$$
LANGUAGE sql;
尝试通过 CTE 来完成，这本来会非常优雅，但无法弄清楚如何在不发生与无法在递归中聚合相关的错误的情况下做到这一点。
WITH RECURSIVE locations AS (
WITH inventories AS (
WITH measures AS (
SELECT m.inventory_id, json_agg(json_build_object(
'id', m.id,
'quantity', m.quantity,
'read', TRUNC(EXTRACT(EPOCH FROM m.read_date)),
'created', TRUNC(EXTRACT(EPOCH FROM m.created)),
'updated', TRUNC(EXTRACT(EPOCH FROM m.updated)),
'deleted', TRUNC(EXTRACT(EPOCH FROM m.deleted))
)) as measures
FROM measure m
GROUP BY m.inventory_id
)
SELECT i.location_id, json_agg(json_build_object(
'id', i.id,
'product_id', p.id,
'name', p.name,
'mass_quantity', p.mass_quantity,
'mass_unit', um.code,
'count_unit', uc.code,
'thumb', p.product_picture_uri,
'sort_order', i.sort_order,
'par_level', i.par_level,
'created', TRUNC(EXTRACT(EPOCH FROM i.created)),
'updated', TRUNC(EXTRACT(EPOCH FROM i.updated)),
'deleted', TRUNC(EXTRACT(EPOCH FROM i.deleted)),
'measures', COALESCE(m.measures, '[]')
)) AS inventories
FROM inventory i
INNER JOIN product p ON i.product_id = p.id
LEFT JOIN unit um ON p.mass_unit_id = um.id
LEFT JOIN unit uc ON p.count_unit_id = uc.id
LEFT JOIN measures m ON i.id = m.inventory_id
GROUP BY i.location_id
)
SELECT null as id, null as name, null as type, null as inventories
FROM location l
INNER JOIN location_type t ON l.location_type_id = t.id
LEFT OUTER JOIN inventories i ON l.id = i.location_id
GROUP BY l.parent_id
/*UNION ALL
SELECT p.id, p.parent_id, p.name, t.code, COALESCE(i.inventories, '[]')::jsonb AS inventories, json_agg(row_to_json(c.*))
FROM location p
INNER JOIN location_type t ON p.location_type_id = t.id
LEFT OUTER JOIN inventories i ON p.id = i.location_id
INNER JOIN locations c ON p.id = c.parent_id
GROUP BY p.id, p.name, t.code, COALESCE(i.inventories, '[]')::jsonb*/
)
SELECT * FROM locations
