json_populate_recordset()

Basic usage example for json_populate_recordset():

postgres=# CREATE TYPE foobar AS (id INT, val TEXT);
CREATE TYPE

postgres=# SELECT * FROM json_populate_recordset(NULL::foobar,  '[{"id":1,"val":"foo"}, {"id":2,"val":"bar"}]');
 id | val 
----+-----
  1 | foo
  2 | bar
(2 rows)

NULL values will be emitted if the provided JSON object does not contain a field matching the expected column name:

postgres=# SELECT id IS NULL, id, val IS NULL, val
             FROM json_populate_recordset(NULL::foobar,  '[{"a":1,"val":"foo"}, {"id":2,"b":"bar"}]');
 ?column? | id | ?column? | val 
----------+----+----------+-----
 t        |    | f        | foo
 f        |  2 | t        | 
(2 rows)

An ERROR will be raised if the JSON object contains values which cannot be cast to the expected column data type:

postgres=# SELECT * FROM json_populate_recordset(NULL::foobar,  '[{"id":"baz","val":"foo"}, {"id":2,"val":"bar"}]');
ERROR:  invalid input syntax for type integer: "baz"

• PostgreSQL documentation: JSON Processing Functions