Appending (pushing) and removing from a JSON array in PostgreSQL 9.5+

Question

For versions less than 9.5 see this question

I have created a table in PostgreSQL using this:

CREATE TEMP TABLE jsontesting
AS
  SELECT id, jsondata::jsonb FROM ( VALUES
    (1, '["abra","value","mango", "apple", "sample"]'),
    (2, '["japan","china","india", "russia", "australia"]'),
    (3, '["must", "match"]'),
    (4, '["abra","value","true", "apple", "sample"]'),
    (5, '["abra","false","mango", "apple", "sample"]'),
    (6, '["string","value","mango", "apple", "sample"]'),
    (7, '["must", "watch"]')
  ) AS t(id,jsondata);

Now what I wanted was to

• add Something like append_to_json_array takes in the actual jsondata which is a json-array and the newString which I have to add to that jsondata array and this function should return the updated json-array.

   UPDATE jsontesting SET jsondata=append_to_json_array(jsondata, 'newString') WHERE id = 7;

• remove a value from the json data array, one function for removing the value.

I tried to search documentation of PostgreSQL but found nothing there.

Answer 1

To add the value use the JSON array append opperator ( || )

UPDATE jsontesting
SET jsondata = jsondata || '["newString"]'::jsonb
WHERE id = 7;

Removing the value looks like this

UPDATE jsontesting
SET jsondata = jsondata - 'newString'
WHERE id = 7; 

Concatenating to a nested field looks like this

UPDATE jsontesting
SET jsondata = jsonb_set(
  jsondata::jsonb,
  array['nestedfield'],
  (jsondata->'nestedfield')::jsonb || '["newString"]'::jsonb) 
WHERE id = 7;

Answer 2

To add to Evan Carroll's answer, you may want to do the following to set the column to an empty array if it is NULL . The append operator ( || ) does nothing if the column is currently NULL .

UPDATE jsontesting SET jsondata = (
    CASE
        WHEN jsondata IS NULL THEN '[]'::JSONB
        ELSE jsondata
    END
) || '["newString"]'::JSONB WHERE id = 7;

Answer 3

I was facing similar issue to append to an existing json data in postgres with new key-value pair. I was able to fix this using append operator ||as follows:

UPDATE jsontesting
SET jsondata = jsondata::jsonb || '{"add_new_data": true}'
WHERE id = 7;