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9.15. JSON Functions and Operators
Table 9-42 shows the operators that are available for use with the two JSON data types (see Section 8.14).
Table 9-42. json and jsonb Operators
| -> | int | Get JSON array element (indexed from zero, negative integers count from the end) | '[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json->2 | {"c":"baz"} |
| -> | text | Get JSON object field by key | '{"a": {"b":"foo"}}'::json->'a' | {"b":"foo"} |
| ->> | int | Get JSON array element as text | '[1,2,3]'::json->>2 | 3 |
| ->> | text | Get JSON object field as text | '{"a":1,"b":2}'::json->>'b' | 2 |
| #> | text[] | Get JSON object at specified path | '{"a": {"b":{"c": "foo"}}}'::json#>'{a,b}' | {"c": "foo"} |
| #>> | text[] | Get JSON object at specified path as text | '{"a":[1,2,3],"b":[4,5,6]}'::json#>>'{a,2}' | 3 |
The standard comparison operators shown in Table 9-1 are available for jsonb, but not for json. They follow the ordering rules for B-tree operations outlined at Section 8.14.4.
Some further operators also exist only for jsonb, as shown in Table 9-43. Many of these operators can be indexed by jsonb operator classes. For a full description of jsonb containment and existence semantics, see Section 8.14.3. Section 8.14.4 describes how these operators can be used to effectively index jsonb data.
Table 9-43. Additional jsonb Operators
| @> | jsonb | Does the left JSON value contain the right JSON path/value entries at the top level? | '{"a":1, "b":2}'::jsonb @> '{"b":2}'::jsonb |
| <@ | jsonb | Are the left JSON path/value entries contained at the top level within the right JSON value? | '{"b":2}'::jsonb <@ '{"a":1, "b":2}'::jsonb |
| ? | text | Does the string exist as a top-level key within the JSON value? | '{"a":1, "b":2}'::jsonb ? 'b' |
| ?| | text[] | Do any of these array strings exist as top-level keys? | '{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'c'] |
| ?& | text[] | Do all of these array strings exist as top-level keys? | '["a", "b"]'::jsonb ?& array['a', 'b'] |
| || | jsonb | Concatenate two jsonb values into a new jsonb value | '["a", "b"]'::jsonb || '["c", "d"]'::jsonb |
| - | text | Delete key/value pair or string element from left operand. Key/value pairs are matched based on their key value. | '{"a": "b"}'::jsonb - 'a' |
| - | integer | Delete the array element with specified index (Negative integers count from the end). Throws an error if top level container is not an array. | '["a", "b"]'::jsonb - 1 |
| #- | text[] | Delete the field or element with specified path (for JSON arrays, negative integers count from the end) | '["a", {"b":1}]'::jsonb #- '{1,b}' |
Table 9-44 shows the functions that are available for creating json and jsonb values. (There are no equivalent functions for jsonb, of the row_to_json and array_to_json functions. However, the to_jsonb function supplies much the same functionality as these functions would.)
Table 9-44. JSON Creation Functions
to_json(anyelement) to_jsonb(anyelement) | Returns the value as json or jsonb. Arrays and composites are converted (recursively) to arrays and objects; otherwise, if there is a cast from the type tojson, the cast function will be used to perform the conversion; otherwise, a scalar value is produced. For any scalar type other than a number, a Boolean, or a null value, the text representation will be used, in such a fashion that it is a valid json or jsonb value. | to_json('Fred said "Hi."'::text) | "Fred said \"Hi.\"" |
| array_to_json(anyarray [, pretty_bool]) | Returns the array as a JSON array. A PostgreSQL multidimensional array becomes a JSON array of arrays. Line feeds will be added between dimension-1 elements if pretty_bool is true. | array_to_json('{{1,5},{99,100}}'::int[]) | [[1,5],[99,100]] |
| row_to_json(record [, pretty_bool]) | Returns the row as a JSON object. Line feeds will be added between level-1 elements if pretty_bool is true. | row_to_json(row(1,'foo')) | {"f1":1,"f2":"foo"} |
json_build_array(VARIADIC "any") jsonb_build_array(VARIADIC "any") | Builds a possibly-heterogeneously-typed JSON array out of a variadic argument list. | json_build_array(1,2,'3',4,5) | [1, 2, "3", 4, 5] |
json_build_object(VARIADIC "any") jsonb_build_object(VARIADIC "any") | Builds a JSON object out of a variadic argument list. By convention, the argument list consists of alternating keys and values. | json_build_object('foo',1,'bar',2) | {"foo": 1, "bar": 2} |
json_object(text[]) jsonb_object(text[]) | Builds a JSON object out of a text array. The array must have either exactly one dimension with an even number of members, in which case they are taken as alternating key/value pairs, or two dimensions such that each inner array has exactly two elements, which are taken as a key/value pair. | json_object('{a, 1, b, "def", c, 3.5}') json_object('{{a, 1},{b, "def"},{c, 3.5}}') | {"a": "1", "b": "def", "c": "3.5"} |
json_object(keys text[], values text[]) jsonb_object(keys text[], values text[]) | This form of json_object takes keys and values pairwise from two separate arrays. In all other respects it is identical to the one-argument form. | json_object('{a, b}', '{1,2}') | {"a": "1", "b": "2"} |
Table 9-45 shows the functions that are available for processing json and jsonb values.
Table 9-45. JSON Processing Functions
json_array_length(json) jsonb_array_length(jsonb) | int | Returns the number of elements in the outermost JSON array. | json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]') | 5 |
json_each(json) jsonb_each(jsonb) | setof key text, value json setof key text, value jsonb | Expands the outermost JSON object into a set of key/value pairs. | select * from json_each('{"a":"foo", "b":"bar"}') | key | value |
json_each_text(json) jsonb_each_text(jsonb) | setof key text, value text | Expands the outermost JSON object into a set of key/value pairs. The returned values will be of type text. | select * from json_each_text('{"a":"foo", "b":"bar"}') | key | value |
json_extract_path(from_json json, VARIADIC path_elems text[]) jsonb_extract_path(from_json jsonb, VARIADIC path_elems text[]) | json jsonb | Returns JSON value pointed to by path_elems(equivalent to #> operator). | json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}','f4') | {"f5":99,"f6":"foo"} |
json_extract_path_text(from_json json, VARIADIC path_elems text[]) jsonb_extract_path_text(from_json jsonb, VARIADIC path_elems text[]) | text | Returns JSON value pointed to by path_elems as text(equivalent to #>>operator). | json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}','f4', 'f6') | foo |
json_object_keys(json) jsonb_object_keys(jsonb) | setof text | Returns set of keys in the outermost JSON object. | json_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}}') | json_object_keys |
json_populate_record(base anyelement, from_json json) jsonb_populate_record(base anyelement, from_json jsonb) | anyelement | Expands the object infrom_json to a row whose columns match the record type defined by base (see note below). | select * from json_populate_record(null::myrowtype, '{"a":1,"b":2}') | a | b |
json_populate_recordset(base anyelement, from_json json) jsonb_populate_recordset(base anyelement, from_json jsonb) | setof anyelement | Expands the outermost array of objects infrom_json to a set of rows whose columns match the record type defined bybase (see note below). | select * from json_populate_recordset(null::myrowtype, '[{"a":1,"b":2},{"a":3,"b":4}]') | a | b |
json_array_elements(json) jsonb_array_elements(jsonb) | setof json setof jsonb | Expands a JSON array to a set of JSON values. | select * from json_array_elements('[1,true, [2,false]]') | value |
json_array_elements_text(json) jsonb_array_elements_text(jsonb) | setof text | Expands a JSON array to a set of text values. | select * from json_array_elements_text('["foo", "bar"]') | value |
json_typeof(json) jsonb_typeof(jsonb) | text | Returns the type of the outermost JSON value as a text string. Possible types are object, array,string, number, boolean, and null. | json_typeof('-123.4') | number |
json_to_record(json) jsonb_to_record(jsonb) | record | Builds an arbitrary record from a JSON object (see note below). As with all functions returning record, the caller must explicitly define the structure of the record with an AS clause. | select * from json_to_record('{"a":1,"b":[1,2,3],"c":"bar"}') as x(a int, b text, d text) | a | b | d |
json_to_recordset(json) jsonb_to_recordset(jsonb) | setof record | Builds an arbitrary set of records from a JSON array of objects (see note below). As with all functions returning record, the caller must explicitly define the structure of the record with an AS clause. | select * from json_to_recordset('[{"a":1,"b":"foo"},{"a":"2","c":"bar"}]') as x(a int, b text); | a | b |
json_strip_nulls(from_json json) jsonb_strip_nulls(from_json jsonb) | json jsonb | Returns from_json with all object fields that have null values omitted. Other null values are untouched. | json_strip_nulls('[{"f1":1,"f2":null},2,null,3]') | [{"f1":1},2,null,3] |
jsonb_set(target jsonb, path text[], new_value jsonb[,create_missing boolean]) | jsonb | Returns target with the section designated by pathreplaced by new_value, or with new_value added ifcreate_missing is true ( default is true) and the item designated by pathdoes not exist. As with the path orientated operators, negative integers that appear in path count from the end of JSON arrays. | jsonb_set('[{"f1":1,"f2":null},2,null,3]', '{0,f1}','[2,3,4]', false) jsonb_set('[{"f1":1,"f2":null},2]', '{0,f3}','[2,3,4]') | [{"f1":[2,3,4],"f2":null},2,null,3] [{"f1": 1, "f2": null, "f3": [2, 3, 4]}, 2] |
jsonb_insert(target jsonb, path text[], new_value jsonb, [insert_after boolean]) | jsonb | Returns target withnew_value inserted. Iftarget section designated by path is in a JSONB array,new_value will be inserted before target or after ifinsert_after is true (default is false). Iftarget section designated by path is in JSONB object,new_value will be inserted only if target does not exist. As with the path orientated operators, negative integers that appear in path count from the end of JSON arrays. | jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"') jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"', true) | {"a": [0, "new_value", 1, 2]} {"a": [0, 1, "new_value", 2]} |
jsonb_pretty(from_json jsonb) | text | Returns from_json as indented JSON text. | jsonb_pretty('[{"f1":1,"f2":null},2,null,3]') | [ |
See also Section 9.20 for the aggregate function json_agg which aggregates record values as JSON, and the aggregate function json_object_agg which aggregates pairs of values into a JSON object, and their jsonb equivalents, jsonb_agg and jsonb_object_agg.
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