Using the ||
operator yields the following result:
select '{"a":{"b":2}}'::jsonb || '{"a":{"c":3}}'::jsonb ;
?column?
-----------------
{"a": {"c": 3}}
(1 row)
I would like to be able to do achieve the following result (??
just a placeholder for the operator):
select '{"a":{"b":2}}'::jsonb ?? '{"a":{"c":3}}'::jsonb ;
?column?
-----------------
{"a": {"b": 2, "c": 3}}
(1 row)
So, you can see the top-level a
key has its child values "merged" such that the result contains both b
and c
.
How do you "deep" merge two JSONB values in Postgres?
Is this possible, if so how?
A more complex test case:
select '{"a":{"b":{"c":3},"z":true}}'::jsonb ?? '{"a":{"b":{"d":4},"z":false}}'::jsonb ;
?column?
-----------------
{"a": {"b": {"c": 3, "d": 4}, "z": false}}
(1 row)
Another test case where a primitive "merges over" and object:
select '{"a":{"b":{"c":3},"z":true}}'::jsonb ?? '{"a":{"b":false,"z":false}}'::jsonb ;
?column?
-----------------
{"a": {"b": false, "z": false}}
(1 row)
After PostgreSQL 9.5 you can use jsonb_set
function:
'{a,c}'
looking into path if it is not there, it will created.'{"a":{"c":3}}'::jsonb#>'{a,c}'
this will get the value of cnew_value added if create_missing is true ( default is true)
Hier is document jsonb -functions
select jsonb_set('{"a":{"b":2}}', '{a,c}','{"a":{"c":3}}'::jsonb#>'{a,c}' )
Result: {"a":{"c":3,"b":2}}
Merge more attribute at once:
with jsonb_paths(main_part,missing_part) as (
values ('{"a":{"b":2}}','{"a":{"c":3,"d":4}}')
)
select jsonb_object_agg(t.k,t.v||t2.v)
from jsonb_paths,
jsonb_each(main_part::jsonb) t(k,v),
jsonb_each(missing_part::jsonb) t2(k,v);
result: {"a":{"c":3,"b":2,"d":4}}
You should merge unnested elements using jsonb_each()
for both values. Doing this in a non-trivial query may be uncomfortable, so I would prefer a custom function like this one:
create or replace function jsonb_my_merge(a jsonb, b jsonb)
returns jsonb language sql as $$
select
jsonb_object_agg(
coalesce(ka, kb),
case
when va isnull then vb
when vb isnull then va
else va || vb
end
)
from jsonb_each(a) e1(ka, va)
full join jsonb_each(b) e2(kb, vb) on ka = kb
$$;
Use:
select jsonb_my_merge(
'{"a":{"b":2}, "d": {"e": 10}, "x": 1}'::jsonb,
'{"a":{"c":3}, "d": {"f": 11}, "y": 2}'::jsonb
)
jsonb_my_merge
------------------------------------------------------------------
{"a": {"b": 2, "c": 3}, "d": {"e": 10, "f": 11}, "x": 1, "y": 2}
(1 row)
You can slightly modify the function using recursion to get a solution working on any level of nesting:
create or replace function jsonb_recursive_merge(a jsonb, b jsonb)
returns jsonb language sql as $$
select
jsonb_object_agg(
coalesce(ka, kb),
case
when va isnull then vb
when vb isnull then va
when jsonb_typeof(va) <> 'object' then va || vb
else jsonb_recursive_merge(va, vb)
end
)
from jsonb_each(a) e1(ka, va)
full join jsonb_each(b) e2(kb, vb) on ka = kb
$$;
Examples:
select jsonb_recursive_merge(
'{"a":{"b":{"c":3},"x":5}}'::jsonb,
'{"a":{"b":{"d":4},"y":6}}'::jsonb);
jsonb_recursive_merge
------------------------------------------------
{"a": {"b": {"c": 3, "d": 4}, "x": 5, "y": 6}}
(1 row)
select jsonb_recursive_merge(
'{"a":{"b":{"c":{"d":{"e":1}}}}}'::jsonb,
'{"a":{"b":{"c":{"d":{"f":2}}}}}'::jsonb)
jsonb_recursive_merge
----------------------------------------------
{"a": {"b": {"c": {"d": {"e": 1, "f": 2}}}}}
(1 row)
Finally, the variant of the function with changes proposed by OP (see comments below):
create or replace function jsonb_recursive_merge(a jsonb, b jsonb)
returns jsonb language sql as $$
select
jsonb_object_agg(
coalesce(ka, kb),
case
when va isnull then vb
when vb isnull then va
when jsonb_typeof(va) <> 'object' or jsonb_typeof(vb) <> 'object' then vb
else jsonb_recursive_merge(va, vb) end
)
from jsonb_each(a) e1(ka, va)
full join jsonb_each(b) e2(kb, vb) on ka = kb
$$;
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