How to sum a value in a JSONB array in Postgresql? - sql

Question

Given the following data in the jsonb column p06 in the table ryzom_characters:
-[ RECORD 1 ]------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
p06 | {
"id": 675010,
"cname": "Bob",
"rpjobs": [
{
"progress": 25
},
{
"progress": 13
},
{
"progress": 30
}
]
}
I am attempting to sum the value of progress. I have attempted the following:
SELECT
c.cname AS cname,
jsonb_array_elements(c.p06->'rpjobs')::jsonb->'progress' AS value
FROM ryzom_characters c
Where cid = 675010
ORDER BY value DESC
LIMIT 50;
Which correctly lists the values:
cname | value
--------+-------
Savisi | 30
Savisi | 25
Savisi | 13
(3 rows)
But now I would like to sum these values, which could be null.
How do I correctly sum an object field within an array?
Here is the table structure:
Table "public.ryzom_characters"
Column | Type | Collation | Nullable | Default
---------------+------------------------+-----------+----------+---------
cid | bigint | | |
cname | character varying(255) | | not null |
p06 | jsonb | | |
x01 | jsonb | | |

Answer 1

Use the function jsonb_array_elements() in a lateral join in the from clause:
select cname, sum(coalesce(value, '0')::int) as value
from (
select
p06->>'cname' as cname,
value->>'progress' as value
from ryzom_characters
cross join jsonb_array_elements(p06->'rpjobs')
where cid = 675010
) s
group by cname
order by value desc
limit 50;
You can use left join instead of cross join to protect the query against inconsistent data:
left join jsonb_array_elements(p06->'rpjobs')
on jsonb_typeof(p06->'rpjobs') = 'array'
where p06->'rpjobs' <> 'null'

Answer 2

The function jsonb_array_elements() is a set-returning function. You should therefore use it as a row source (in the FROM clause). After the call you have a table where every row contains an array element. From there on it is relatively easy.
SELECT cname,
sum(coalesce(r.prog->>'progress'::int, 0)) AS value
FROM ryzom_characters c,
jsonb_array_elements(c.p06->'rpjobs') r (prog)
WHERE c.cid = 675010
GROUP BY cname
ORDER BY value DESC
LIMIT 50;