Transform JSON array to a JSON map - json

Question

I have a postgresql table called datasource with jsonb column called config. It has the following structure:
{
"url":"some_url",
"password":"some_password",
"username":"some_username",
"projectNames":[
"project_name_1",
...
"project_name_N"
]
}
I would like to transform nested json array projectNames into a map and add a default value for each element from the array, so it would look like:
{
"url":"some_url",
"password":"some_password",
"username":"some_username",
"projectNames":{
"project_name_1": "value",
...
"project_name_N": "value"
}
}
I have selected projectNames from the table using postgresql jsonb operator config#>'{projectNames}', but I have no idea how to perform transform operation.
I think, I should use something like jsonb_object_agg, but it converts all data into a single row.
I'm using PostgreSQL 9.6 version.

Answer 1

You need to first unnest the array, then build a new JSON document from that. Then you can put that back into the column.
update datasource
set config = jsonb_set(config, '{projectNames}', t.map)
from (
select id, jsonb_object_agg(pn.n, 'value') as map
from datasource, jsonb_array_elements_text(config -> 'projectNames') as pn (n)
group by id
) t
where t.id = datasource.id;
The above assumes that there is a primary (or at least unique) column named id. The inner select transforms the array into a map.
Online example: http://rextester.com/GPP85654

Answer 2

are you looking for smth like:
t=# with c(j) as (values('{
"url":"some_url",
"password":"some_password",
"username":"some_username",
"projectNames":[
"project_name_1",
"project_name_N"
]
}
'::jsonb))
, n as (select j,jsonb_array_elements_text(j->'projectNames') a from c)
select jsonb_pretty(jsonb_set(j,'{projectNames}',jsonb_object_agg(a,'value'))) from n group by j
;
jsonb_pretty
------------------------------------
{ +
"url": "some_url", +
"password": "some_password", +
"username": "some_username", +
"projectNames": { +
"project_name_1": "value",+
"project_name_N": "value" +
} +
}
(1 row)
Time: 19.756 ms
if so, look at:
https://www.postgresql.org/docs/current/static/functions-aggregate.html
https://www.postgresql.org/docs/current/static/functions-json.html