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json_populate_recordset()

A function expanding a JSON object array to a set of rows

json_populate_recordset() is a system function expanding the top-level JSON array of objects to a set of rows.

json_populate_recordset() was added in PostgreSQL 9.3.

Usage

json_populate_recordset ( base anyelement, from_json json ) → setof anyelement

The base parameter must be a composite type whose column names correspond to JSON fields.

Change history

Examples

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"

Categories

JSON, System function

See also

jsonb_populate_recordset(), json_populate_record(), json_to_recordset()