Delete element in a deeply nested array in jsonb column - Postgres - sql

Question

I have a table my_table with a jsonb column that contains some data, for instance, in a single row, the column can contain the following data:
[
{
"x_id": "1",
"type": "t1",
"parts": [
{ "part_id": "1", price: 400 },
{ "part_id": "2", price: 500 },
{ "part_id": "3", price: 0 }
]
},
{
"x_id": "2",
"type": "t1",
"parts": [
{ "part_id": "1", price: 1000 },
{ "part_id": "3", price: 60 }
]
},
{
"x_id": "3",
"type": "t2",
"parts": [
{ "part_id": "1", price: 100 },
{ "part_id": "3", price: 780 },
{ "part_id": "2", price: 990 }
]
}
]
I need help finding how to delete an element from the parts array given a x_id and a part_id.
Example
given x_id=2 and part_id=1, I need the data to be updated to become:
[
{
"x_id": "1",
"type": "t1",
"parts": [
{ "part_id": "1", price: 400 },
{ "part_id": "2", price: 500 },
{ "part_id": "3", price: 0 }
]
},
{
"x_id": "2",
"type": "t1",
"parts": [
{ "part_id": "3", price: 60 }
]
},
{
"x_id": "3",
"type": "t2",
"parts": [
{ "part_id": "1", price: 100 },
{ "part_id": "3", price: 780 },
{ "part_id": "2", price: 990 }
]
}
]
PS1: these data cannot be normalized, so that's not a possible solution.
PS2: I'm running PostgreSQL 9.6
PS3: I have checked this question and this question but my data structure seems too complex compared to the other questions thus I can't apply the given answers.
Edit1: the json data can be big, especially the parts array, which can have from as few as 0 element to thousands.

Answer 1

I think you can use #- operator (see functions-json), you just need to find the path to remove the array element from:
select
data #- p.path
from test as t
cross join lateral (
select array[(a.i-1)::text,'parts',(b.i-1)::text]
from jsonb_array_elements(t.data) with ordinality as a(data,i),
jsonb_array_elements(a.data->'parts') with ordinality as b(data,i)
where
a.data ->> 'x_id' = '2' and
b.data ->> 'part_id' = '1'
) as p(path)
or
update test as t set
data = data #- (
select
array[(a.i-1)::text,'parts',(b.i-1)::text]
from jsonb_array_elements(t.data) with ordinality as a(data,i),
jsonb_array_elements(a.data->'parts') with ordinality as b(data,i)
where
a.data ->> 'x_id' = '2' and
b.data ->> 'part_id' = '1'
)
db<>fiddle demo
update Ok, there's reasonable comment that update part works incorrectly if given path doesn't exist in the data. I guess in this case you're going to either duplicate expression in the where clause:
update test as t set
data = data #- (
select
array[(a.i-1)::text,'parts',(b.i-1)::text]
from jsonb_array_elements(t.data) with ordinality as a(data,i),
jsonb_array_elements(a.data->'parts') with ordinality as b(data,i)
where
a.data ->> 'x_id' = '2' and
b.data ->> 'part_id' = '23222'
)
where
exists (
select *
from jsonb_array_elements(t.data) as a(data),
jsonb_array_elements(a.data->'parts') as b(data)
where
a.data ->> 'x_id' = '2' and
b.data ->> 'part_id' = '23222'
)
db<>fiddle demo
or you can use self-join:
update test as t2 set
data = t.data #- p.path
from test as t
cross join lateral (
select array[(a.i-1)::text,'parts',(b.i-1)::text]
from jsonb_array_elements(t.data) with ordinality as a(data,i),
jsonb_array_elements(a.data->'parts') with ordinality as b(data,i)
where
a.data ->> 'x_id' = '2' and
b.data ->> 'part_id' = '23232'
) as p(path)
where
t.ctid = t2.ctid
db<>fiddle demo

Answer 2

This should work, just need another unique column (primary key usually)
create test table
create table test_tab(
id serial primary key,
j jsonb
);
insert into test_tab
(j)
values
('[
{
"x_id": "1",
"type": "t1",
"parts": [
{ "part_id": "1", "price": 400 },
{ "part_id": "2", "price": 500 },
{ "part_id": "3", "price": 0 }
]
},
{
"x_id": "2",
"type": "t1",
"parts": [
{ "part_id": "1", "price": 1000 },
{ "part_id": "3", "price": 60 }
]
},
{
"x_id": "3",
"type": "t2",
"parts": [
{ "part_id": "1", "price": 100 },
{ "part_id": "3", "price": 780 },
{ "part_id": "2", "price": 990 }
]
}
]');
Then split json, filter unnecessary data, and recreate json again:
select id, jsonb_agg( jsonb_build_object('x_id',xid, 'type',type, 'parts', case when inner_arr = '[null]'::jsonb then parts_arr::jsonb else inner_arr end) )
from (
select
id,
value->>'x_id' as xid,
jsonb_agg(inner_arr) as inner_arr,
max(value->>'parts') as parts_arr,
max(value->>'type') as type
from (
select * ,
case when value->>'x_id'='2' then jsonb_array_elements(value->'parts') else NULL end inner_arr
from test_tab
join lateral jsonb_array_elements(j)
on true
) t
where
inner_arr->>'part_id' is distinct from '1'
group by id, value->>'x_id'
) t
group by id