PostgreSQL: Remove attribute from JSON column

Question

I need to remove some attributes from a json type column.

The Table:

CREATE TABLE my_table( id VARCHAR(80), data json);
INSERT INTO my_table (id, dat         


        

Answer 1

This has gotten much easier with PostgreSQL 9.5 using the JSONB type. See JSONB operators documented here.

You can remove a top-level attribute with the "-" operator.

SELECT '{"a": {"key":"value"}, "b": 2, "c": true}'::jsonb - 'a'
// -> {"b": 2, "c": true}

You can use this within an update call to update an existing JSONB field.

UPDATE my_table SET data = data - 'attrB'

You can also provide the attribute name dynamically via parameter if used in a function.

CREATE OR REPLACE FUNCTION delete_mytable_data_key(
    _id integer,
    _key character varying)
  RETURNS void AS
$BODY$
BEGIN
    UPDATE my_table SET
        data = data - _key
    WHERE id = _id;
END;
$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;

The reverse operator is the "||", in order to concatenate two JSONB packets together. Note that the right-most use of the attribute will overwrite any previous ones.

SELECT '{"a": true, "c": true}'::jsonb || '{"a": false, "b": 2}'::jsonb 
// -> {"a": false, "b": 2, "c": true}