Postgres jsonb array join - arrays

Question

I have a jsonb document in a table. This document has an array of cameraIds in the document. I am trying to join this data with the cameras table that is a normal table where cameraId is a column, and return unique rows from the table with the jsonb column (why I am using a group by in my query).
Any advice on how to optimize this query for performance would be greatly appreciated.
JSONB Col Example:
{
"date": {
"end": "2018-11-02T22:00:00.000Z",
"start": "2018-11-02T14:30:00.000Z"
},
"cameraIds": [100, 101],
"networkId": 5,
"filters": [],
"includeUnprocessed": true,
"reason": "some reason",
"vehicleFilter": {
"bodyInfo": "something",
"lpInfo": "something"
}
}
Query:
select ssr.id,
a.name as user_name,
ssr.start_date,
ssr.end_date,
ssr.created_at,
ssr.payload -> 'filters' as pretty_filters,
ssr.payload -> 'reason' as reason,
ssr.payload -> 'includePlates' as include_plates,
ssr.payload -> 'vehicleFilter' -> 'bodyInfo' as vbf,
ssr.payload -> 'vehicleFilter' -> 'lpInfo' as lpInfo,
array_agg(n.name) filter (where n.organization_id = ${orgId}) as network_names,
array_agg(c.name) filter (where n.organization_id = ${orgId}) as camera_names
from
ssr
cross join jsonb_array_elements(ssr.payload -> 'cameraIds') camera_id
inner join cameras as c on c.id = camera_id::int
inner join networks as n on n.id = c.network_id
inner join accounts as a on ssr.account_id = a.id
where n.organization_id = ${someId}
and ssr.created_at between ${startDate} and ${endDat}
group by 1,2,3,4,5,6,7,8,9,10
order BY ssr.created_at desc
OFFSET 0
LIMIT 25;

Answer 1

Your query says:
where n.organization_id = ${someId}
But then the aggregate FILTER says:
where n.organization_id = ${orgId}
... which is a contradiction. The aggregated arrays would always be empty - except where ${orgId} happens to be the same as ${someId}, but then the FILTER clause is useless noise. IOW, the query doesn't seem to make sense as given.
The query might make sense after dropping the aggregate FILTER clauses:
SELECT s.id
, a.name AS user_name
, s.start_date
, s.end_date
, s.created_at
, s.payload ->> 'filters' AS pretty_filters
, s.payload ->> 'reason' AS reason
, s.payload ->> 'includePlates' AS include_plates
, s.payload -> 'vehicleFilter' ->> 'bodyInfo' AS vbf
, s.payload -> 'vehicleFilter' ->> 'lpInfo' AS lpInfo
, cn.camera_names
, cn.network_names
FROM ssr s
JOIN accounts a ON a.id = s.account_id -- assuming referential integrity
CROSS JOIN LATERAL (
SELECT array_agg(c.name) AS camera_names -- sort order?
, array_agg(n.name) AS network_names -- same order? distinct?
FROM jsonb_array_elements_text(ssr.payload -> 'cameraIds') i(camera_id)
JOIN cameras c ON c.id = i.camera_id::int
JOIN networks n ON n.id = c.network_id
WHERE n.organization_id = ${orgId}
) cn
WHERE s.created_at BETWEEN ${startDate} AND ${endDate} -- ?
ORDER BY s.created_at DESC NULLS LAST
LIMIT 25;
Key is the LATERAL subquery, which avoids duplication of rows from ssr, so we can also drop the outer GROUP BY. Should be considerably faster.
Also note ->> instead of -> and jsonb_array_elements_text(). See:
How to turn JSON array into Postgres array?
I left some question marks at more dubious spots in the query. Notably, BETWEEN is almost always the wrong tool for timestamps. See:
Subtract hours from the now() function