Add element to JSON object in Postgres

use || to merge jsonb and set the value to it

example:

origin:

in table a:

id | info

1 | {"aa":"bb"}

2 | {"aa":"cc"}

after executing:

update a set info = info::jsonb || ('{"id":' || id || '}' )::jsonb 

generates:

id | info

1 | {"aa":"bb","id":1}

2 | {"aa":"cc","id":2}

something_else:

1. use - ‘key’ to delete element in jsonb
2. merge will replace origin one if the two jsonb has same key

If you upgrade to PG9.5.1, then you can use sql operator || to merge jsonb, example

select '{"a":1}'::jsonb || '{"a":2, "b":2}'::jsonb

will return {"a": 2, "b": 2}

If you can't upgrade to pg9.5.1, IMHO, doing the job in your code will be a better choice. You can parse old jsonb string as a map, and then update the map, then convert to string and update db-record.

And if we want to update (add) a JSONB field:

UPDATE <table>
SET <field-name> = <field-name> || '{"a": 1}'::jsonb
WHERE id = <some id>

Even I had the same problem, I wanted to dynamically append new elements to jsonb[].

Assume column_jsonb[] = [{"name":"xyz","age":"12"}]

UPDATE table_name
   SET column_jsonb[] = array_append(column_jsonb[],'{"name":"abc","age":"22"}');

Result : [{"name":"xyz","age":"12"},{"name":"abc","age":"22"}]