I have table
CREATE TABLE items (
id BIGINT PRIMARY KEY ,
data jsonb
);
Format of data
[
{
"id": "d20fe90c-137c-4713-bde1-2d4e75178ad3",
"text": "text",
"count": 1
},
{
"id": "d20fe90c-137c-4713-bde1-2d4e75178ad4",
""text": "text",
"count": 1
}
]
How I can remove field count from all elements of data json array?
I try
UPDATE items
SET data = data #- '{count}';
But this query requires index of array element before count as
UPDATE items
SET data = data #- '{0, count}';
There is no operator or built-in function to do that. Unnest the array and aggregate modified elements in the way like this:
update items t
set data = (
select jsonb_agg(elem- 'count')
from items
cross join lateral jsonb_array_elements(data) as arr(elem)
where id = t.id)
Test it in db<>fiddle.
Related
I am creating a temp table in a PostgreSQL function\proc.
CREATE TEMP TABLE tbl_temp_class(id SERIAL PRIMARY key, batch_id INT, class_id INT, class_name VARCHAR);
later I am dynamically adding columns to this table, using dynamic sql.
the l_column_counter is incremented with in a for loop untill n
l_sql_query := CONCAT('ALTER TABLE tbl_temp_class ADD column ', 'col', '_', l_column_counter, ' varchar default('''');');
EXECUTE l_sql_query;
At then end I want the tbl_temp_class result as a json array. Hence I'm doing below.
select json_agg(ut)
from (
select *
from tbl_temp_class
order by id) ut;
I expect the result for the above query to be
[
{
"id":1,
"batch_id":1,
"class_id":1,
"class_name":"Maths",
"col_1":"",
"col_2":"",
"col_3":"",
"col_4":"",
"col_5":""
},
{
"id":2,
"batch_id":1,
"class_id":2,
"class_name":"History",
"col_1":"",
"col_2":"",
"col_3":"",
"col_4":"",
"col_5":""
}
]
however, the result I am getting is as below. The column display order is scrambled.
Any idea how to fix this? Is this because the json is generated out of a temp table?
I need the column display order in the final json array to be same as the column display order in the temp table.
[
{
"id":1,
"col_1":"",
"col_2":"",
"col_3":"",
"col_4":"",
"col_5":"",
"class_id":1,
"batch_id":1,
"class_name":"Maths",
},
{
"id":2,
"col_1":"",
"col_2":"",
"col_3":"",
"col_4":"",
"col_5":"",
"class_id":2,
"batch_id":1,
"class_name":"History",
}
]
Did you try an ORDER BY in the aggregation?
SELECT json_agg(ut ORDER BY id) -- this where you want to use the ORDER BY
FROM (
SELECT *
FROM tbl_temp_class
ORDER BY id) ut;
I've got a JSON column in Postgres, that contains data in the following structure
{
"listings": [{
"id": "KTyneMdrAhAEKyC9Aylf",
"active": true
},
{
"id": "ZcjK9M4tuwhWWdK8WcfX",
"active": false
}
]
}
I need to do a few things, all of which I am unsure how to do
Add a new object to the listings array
Remove an object from the listings array based on its id
Update an object in the listings array based on its id
I am also using Sequelize if there are any built in functions to do this (I can't see anything obvious)
demo:db<>fiddle
Insert (jsonb_insert()):
UPDATE mytable
SET mydata = jsonb_insert(mydata, '{listings, 0}', '{"id":"foo", "active":true}');
Update (expand array, change value with jsonb_set(), reaggregate):
UPDATE mytable
SET mydata = jsonb_set(mydata, '{listings}', s.a)
FROM
(
SELECT
jsonb_agg(
CASE WHEN elems ->> 'id' = 'foo' THEN jsonb_set(elems, '{active}', 'false')
ELSE elems
END
) as a
FROM
mytable,
jsonb_array_elements(mydata -> 'listings') AS elems
) s;
Delete (expand array, filter relevant elements, reaggregate):
UPDATE mytable
SET mydata = jsonb_set(mydata, '{listings}', s.a)
FROM
(
SELECT
jsonb_agg(elems) as a
FROM
mytable,
jsonb_array_elements(mydata -> 'listings') AS elems
WHERE elems ->> 'id' != 'foo'
) s;
Updating and deleting can be done in one line like the inserting. But in that case you have to use the array element index instead of a certain value. If you want to change an array element with a value you need to read it first. This is only possible with a prior expanding.
i have a table with a jsonb column and documents are like these(simplified)
{
"a": 1,
"rg": [
{
"rti": 2
}
]
}
I want to filter all the rows which has 'rg' field and there is at least one 'rti'field in the array.
My current solution is
log->>'rg' ilike '%rti%'
Is there another approach, probably a faster solution exists.
Another approach would be applying jsonb_each to the jsonb object and then jsonb_array_elements_text to the extracted value from jsonb_each method :
select id, js_value2
from
(
select (js).value as js_value, jsonb_array_elements_text((js).value) as js_value2,id
from
(
select jsonb_each(log) as js, id
from tab
) q
where (js).key = 'rg'
) q2
where js_value2 like '%rti%';
Demo
Table faults contains column recacc (jsonb) which contains an array of json objects. Each of them contains a field action. If the value for action is abc, I want to change it to cba. Changes to be applied to all rows.
[
{
"action": "abc",
"created": 1128154425441
},
{
"action": "lmn",
"created": 1228154425441
},
{
"action": "xyz",
"created": 1328154425441
}
]
The following doesn't work, probably because of the data being in array format
update faults
set recacc = jsonb_set(recacc,'{action}', to_jsonb('cbe'::TEXT),false)
where recacc ->> 'action' = 'abc'
I'm not sure if this is the best option, but you may first get the elements of jsonb using jsonb_array_elements, replace it and then reconstruct the json using array_agg and array_to_json.
UPDATE faults SET recacc = new_recacc::jsonb
FROM
(SELECT array_to_json(array_agg(s)) as new_recacc
FROM
( SELECT
replace(c->>'action','abc','cba') , --this to change the value
c->>'created' FROM faults f
cross join lateral jsonb_array_elements(f.recacc) as c
) as s (action,created)
) m;
Demo
I am very new to the PG jsonb field.
I have for example a jsonb field containing the following
{
"RootModule": {
"path": [
1
],
"tags": {
"ModuleBase1": {
"value": 40640,
"humanstring": "40640"
},
"ModuleBase2": {
"value": 40200,
"humanstring": "40200"
}
},
"children": {
"RtuInfoModule": {
"path": [
1,
0
],
"tags": {
"in0": {
"value": 11172,
"humanstring": "11172"
},
"in1": {
"value": 25913,
"humanstring": "25913"
}
etc....
Is there a way to query X levels deep and search the "tags" key for a certain key.
Say I want "ModuleBase2" and "in1" and I want to get their values?
Basically I am looking for a query that will traverse a jsonb field until it finds a key and returns the value without having to know the structure.
In Python or JS a simple loop or recursive function could easily traverse a json object (or dictionary) until it finds a key.
Is there a built in function PG has to do that?
Ultimately I want to do this in django.
Edit:
I see I can do stuff like
SELECT data.key AS key, data.value as value
FROM trending_snapshot, jsonb_each(trending_snapshot.snapshot-
>'RootModule') AS data
WHERE key = 'tags';
But I must specify the the levels.
You can use a recursive query to flatten a nested jsonb, see this answer. Modify the query to find values for specific keys (add a condition in where clause):
with recursive flat (id, path, value) as (
select id, key, value
from my_table,
jsonb_each(data)
union
select f.id, concat(f.path, '.', j.key), j.value
from flat f,
jsonb_each(f.value) j
where jsonb_typeof(f.value) = 'object'
)
select id, path, value
from flat
where path like any(array['%ModuleBase2.value', '%in1.value']);
id | path | value
----+--------------------------------------------------+-------
1 | RootModule.tags.ModuleBase2.value | 40200
1 | RootModule.children.RtuInfoModule.tags.in1.value | 25913
(2 rows)
Test it in SqlFiddle.