Merging Concatenating JSON(B) columns in query

Question

Using Postgres 9.4, I am looking for a way to merge two (or more) json or jsonb columns in a query. Consider the following table as an example:

Answer 1

This function would merge nested json objects

create or replace function jsonb_merge(CurrentData jsonb,newData jsonb)
 returns jsonb
 language sql
 immutable
as $jsonb_merge_func$
 select case jsonb_typeof(CurrentData)
   when 'object' then case jsonb_typeof(newData)
     when 'object' then (
       select    jsonb_object_agg(k, case
                   when e2.v is null then e1.v
                   when e1.v is null then e2.v
                   when e1.v = e2.v then e1.v 
                   else jsonb_merge(e1.v, e2.v)
                 end)
       from      jsonb_each(CurrentData) e1(k, v)
       full join jsonb_each(newData) e2(k, v) using (k)
     )
     else newData
   end
   when 'array' then CurrentData || newData
   else newData
 end
$jsonb_merge_func$;

Answer 2

Try this, if anyone having an issue for merging two JSON object

select table.attributes::jsonb || json_build_object('foo',1,'bar',2)::jsonb FROM table where table.x='y';

Answer 3

works well as an alternative to || when recursive deep merge is required (found here) :

create or replace function jsonb_merge_recurse(orig jsonb, delta jsonb)
returns jsonb language sql as $$
    select
        jsonb_object_agg(
            coalesce(keyOrig, keyDelta),
            case
                when valOrig isnull then valDelta
                when valDelta isnull then valOrig
                when (jsonb_typeof(valOrig) <> 'object' or jsonb_typeof(valDelta) <> 'object') then valDelta
                else jsonb_merge_recurse(valOrig, valDelta)
            end
        )
    from jsonb_each(orig) e1(keyOrig, valOrig)
    full join jsonb_each(delta) e2(keyDelta, valDelta) on keyOrig = keyDelta
$$;

Answer 4

Looks like nobody proposed this kind of solution yet, so here's my take, usng custom aggregate functions:

create or replace aggregate jsonb_merge_agg(jsonb)
(
    sfunc = jsonb_concat,
    stype = jsonb,
    initcond = '{}'
);

create or replace function jsonb_concat(a jsonb, b jsonb) returns jsonb
    as 'select $1 || $2'
    language sql
    immutable
    parallel safe
;

Note: this is using || which replaces existing values at same path instead of deeply merging them.

Now jsonb_merge_agg is accessible like so:

select jsonb_merge_agg(some_col) from some_table group by something;