I am very new to the PG jsonb field.
I have for example a jsonb field containing the following
{
"RootModule": {
"path": [
1
],
"tags": {
"ModuleBase1": {
"value": 40640,
"humanstring": "40640"
},
"ModuleBase2": {
"value": 40200,
"humanstring": "40200"
}
},
"children": {
"RtuInfoModule": {
"path": [
1,
],
"tags": {
"in0": {
"value": 11172,
"humanstring": "11172"
},
"in1": {
"value": 25913,
"humanstring": "25913"
}
etc....
Is there a way to query X levels deep and search the "tags" key for a certain key.
Say I want "ModuleBase2" and "in1" and I want to get their values?
Basically I am looking for a query that will traverse a jsonb field until it finds a key and returns the value without having to know the structure.
In Python or JS a simple loop or recursive function could easily traverse a json object (or dictionary) until it finds a key.
Is there a built in function PG has to do that?
Ultimately I want to do this in django.
Edit:
I see I can do stuff like
SELECT data.key AS key, data.value as value
FROM trending_snapshot, jsonb_each(trending_snapshot.snapshot-
>'RootModule') AS data
WHERE key = 'tags';
But I must specify the the levels.
解決方案
You can use a recursive query to flatten a nested jsonb, see this answer. Modify the query to find values for specific keys (add a condition in where clause):
with recursive flat (id, path, value) as (
select id, key, value
from my_table,
jsonb_each(data)
union
select f.id, concat(f.path, '.', j.key), j.value
from flat f,
jsonb_each(f.value) j
where jsonb_typeof(f.value) = 'object'
)
select id, path, value
from flat
where path like any(array['%ModuleBase2.value', '%in1.value']);
id | path | value
----+--------------------------------------------------+-------
1 | RootModule.tags.ModuleBase2.value | 40200
1 | RootModule.children.RtuInfoModule.tags.in1.value | 25913
(2 rows)
Test it in SqlFiddle.