Movatterモバイル変換


[0]ホーム

URL:



Facebook
Postgres Pro
Facebook
Downloads
9.16. JSON Functions and Operators
Prev UpChapter 9. Functions and OperatorsHome Next

9.16. JSON Functions and Operators#

This section describes:

  • functions and operators for processing and creating JSON data

  • the SQL/JSON path language

  • the SQL/JSON query functions

To provide native support for JSON data types within the SQL environment,PostgreSQL implements theSQL/JSON data model. This model comprises sequences of items. Each item can hold SQL scalar values, with an additional SQL/JSON null value, and composite data structures that use JSON arrays and objects. The model is a formalization of the implied data model in the JSON specificationRFC 7159.

SQL/JSON allows you to handle JSON data alongside regular SQL data, with transaction support, including:

  • Uploading JSON data into the database and storing it in regular SQL columns as character or binary strings.

  • Generating JSON objects and arrays from relational data.

  • Querying JSON data using SQL/JSON query functions and SQL/JSON path language expressions.

To learn more about the SQL/JSON standard, see[sqltr-19075-6]. For details on JSON types supported inPostgreSQL, seeSection 8.14.

9.16.1. Processing and Creating JSON Data#

Table 9.45 shows the operators that are available for use with JSON data types (seeSection 8.14). In addition, the usual comparison operators shown inTable 9.1 are available forjsonb, though not forjson. The comparison operators follow the ordering rules for B-tree operations outlined inSection 8.14.4. See alsoSection 9.21 for the aggregate functionjson_agg which aggregates record values as JSON, the aggregate functionjson_object_agg which aggregates pairs of values into a JSON object, and theirjsonb equivalents,jsonb_agg andjsonb_object_agg.

Table 9.45. json andjsonb Operators

Operator

Description

Example(s)

json->integerjson

jsonb->integerjsonb

Extractsn'th element of JSON array (array elements are indexed from zero, but negative integers count from the end).

'[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -> 2{"c":"baz"}

'[{"a":"foo"},{"b":"bar"},{"c":"baz"}]'::json -> -3{"a":"foo"}

json->textjson

jsonb->textjsonb

Extracts JSON object field with the given key.

'{"a": {"b":"foo"}}'::json -> 'a'{"b":"foo"}

json->>integertext

jsonb->>integertext

Extractsn'th element of JSON array, astext.

'[1,2,3]'::json ->> 23

json->>texttext

jsonb->>texttext

Extracts JSON object field with the given key, astext.

'{"a":1,"b":2}'::json ->> 'b'2

json#>text[]json

jsonb#>text[]jsonb

Extracts JSON sub-object at the specified path, where path elements can be either field keys or array indexes.

'{"a": {"b": ["foo","bar"]}}'::json #> '{a,b,1}'"bar"

json#>>text[]text

jsonb#>>text[]text

Extracts JSON sub-object at the specified path astext.

'{"a": {"b": ["foo","bar"]}}'::json #>> '{a,b,1}'bar


Note

The field/element/path extraction operators return NULL, rather than failing, if the JSON input does not have the right structure to match the request; for example if no such key or array element exists.

Some further operators exist only forjsonb, as shown inTable 9.46.Section 8.14.4 describes how these operators can be used to effectively search indexedjsonb data.

Table 9.46. Additionaljsonb Operators

Operator

Description

Example(s)

jsonb@>jsonbboolean

Does the first JSON value contain the second? (SeeSection 8.14.3 for details about containment.)

'{"a":1, "b":2}'::jsonb @> '{"b":2}'::jsonbt

jsonb<@jsonbboolean

Is the first JSON value contained in the second?

'{"b":2}'::jsonb <@ '{"a":1, "b":2}'::jsonbt

jsonb?textboolean

Does the text string exist as a top-level key or array element within the JSON value?

'{"a":1, "b":2}'::jsonb ? 'b't

'["a", "b", "c"]'::jsonb ? 'b't

jsonb?|text[]boolean

Do any of the strings in the text array exist as top-level keys or array elements?

'{"a":1, "b":2, "c":3}'::jsonb ?| array['b', 'd']t

jsonb?&text[]boolean

Do all of the strings in the text array exist as top-level keys or array elements?

'["a", "b", "c"]'::jsonb ?& array['a', 'b']t

jsonb||jsonbjsonb

Concatenates twojsonb values. Concatenating two arrays generates an array containing all the elements of each input. Concatenating two objects generates an object containing the union of their keys, taking the second object's value when there are duplicate keys. All other cases are treated by converting a non-array input into a single-element array, and then proceeding as for two arrays. Does not operate recursively: only the top-level array or object structure is merged.

'["a", "b"]'::jsonb || '["a", "d"]'::jsonb["a", "b", "a", "d"]

'{"a": "b"}'::jsonb || '{"c": "d"}'::jsonb{"a": "b", "c": "d"}

'[1, 2]'::jsonb || '3'::jsonb[1, 2, 3]

'{"a": "b"}'::jsonb || '42'::jsonb[{"a": "b"}, 42]

To append an array to another array as a single entry, wrap it in an additional layer of array, for example:

'[1, 2]'::jsonb || jsonb_build_array('[3, 4]'::jsonb)[1, 2, [3, 4]]

jsonb-textjsonb

Deletes a key (and its value) from a JSON object, or matching string value(s) from a JSON array.

'{"a": "b", "c": "d"}'::jsonb - 'a'{"c": "d"}

'["a", "b", "c", "b"]'::jsonb - 'b'["a", "c"]

jsonb-text[]jsonb

Deletes all matching keys or array elements from the left operand.

'{"a": "b", "c": "d"}'::jsonb - '{a,c}'::text[]{}

jsonb-integerjsonb

Deletes the array element with specified index (negative integers count from the end). Throws an error if JSON value is not an array.

'["a", "b"]'::jsonb - 1["a"]

jsonb#-text[]jsonb

Deletes the field or array element at the specified path, where path elements can be either field keys or array indexes.

'["a", {"b":1}]'::jsonb #- '{1,b}'["a", {}]

jsonb@?jsonpathboolean

Does JSON path return any item for the specified JSON value? (This is useful only with SQL-standard JSON path expressions, notpredicate check expressions, since those always return a value.)

'{"a":[1,2,3,4,5]}'::jsonb @? '$.a[*] ? (@ > 2)'t

jsonb@@jsonpathboolean

Returns the result of a JSON path predicate check for the specified JSON value. (This is useful only withpredicate check expressions, not SQL-standard JSON path expressions, since it will returnNULL if the path result is not a single boolean value.)

'{"a":[1,2,3,4,5]}'::jsonb @@ '$.a[*] > 2't


Note

Thejsonpath operators@? and@@ suppress the following errors: missing object field or array element, unexpected JSON item type, datetime and numeric errors. Thejsonpath-related functions described below can also be told to suppress these types of errors. This behavior might be helpful when searching JSON document collections of varying structure.

Table 9.47 shows the functions that are available for constructingjson andjsonb values. Some functions in this table have aRETURNING clause, which specifies the data type returned. It must be one ofjson,jsonb,bytea, a character string type (text,char, orvarchar), or a type that can be cast tojson. By default, thejson type is returned.

Table 9.47. JSON Creation Functions

Function

Description

Example(s)

to_json (anyelement ) →json

to_jsonb (anyelement ) →jsonb

Converts any SQL value tojson orjsonb. Arrays and composites are converted recursively to arrays and objects (multidimensional arrays become arrays of arrays in JSON). Otherwise, if there is a cast from the SQL data type tojson, the cast function will be used to perform the conversion;[a] otherwise, a scalar JSON value is produced. For any scalar other than a number, a Boolean, or a null value, the text representation will be used, with escaping as necessary to make it a valid JSON string value.

to_json('Fred said "Hi."'::text)"Fred said \"Hi.\""

to_jsonb(row(42, 'Fred said "Hi."'::text)){"f1": 42, "f2": "Fred said \"Hi.\""}

array_to_json (anyarray [,boolean] ) →json

Converts an SQL array to a JSON array. The behavior is the same asto_json except that line feeds will be added between top-level array elements if the optional boolean parameter is true.

array_to_json('{{1,5},{99,100}}'::int[])[[1,5],[99,100]]

json_array ( [ {value_expression [FORMAT JSON] } [, ...]] [ {NULL |ABSENT }ON NULL] [RETURNINGdata_type [FORMAT JSON [ENCODING UTF8]]])

json_array ( [query_expression] [RETURNINGdata_type [FORMAT JSON [ENCODING UTF8]]])

Constructs a JSON array from either a series ofvalue_expression parameters or from the results ofquery_expression, which must be a SELECT query returning a single column. IfABSENT ON NULL is specified, NULL values are ignored. This is always the case if aquery_expression is used.

json_array(1,true,json '{"a":null}')[1, true, {"a":null}]

json_array(SELECT * FROM (VALUES(1),(2)) t)[1, 2]

row_to_json (record [,boolean] ) →json

Converts an SQL composite value to a JSON object. The behavior is the same asto_json except that line feeds will be added between top-level elements if the optional boolean parameter is true.

row_to_json(row(1,'foo')){"f1":1,"f2":"foo"}

json_build_array (VARIADIC"any" ) →json

jsonb_build_array (VARIADIC"any" ) →jsonb

Builds a possibly-heterogeneously-typed JSON array out of a variadic argument list. Each argument is converted as perto_json orto_jsonb.

json_build_array(1, 2, 'foo', 4, 5)[1, 2, "foo", 4, 5]

json_build_object (VARIADIC"any" ) →json

jsonb_build_object (VARIADIC"any" ) →jsonb

Builds a JSON object out of a variadic argument list. By convention, the argument list consists of alternating keys and values. Key arguments are coerced to text; value arguments are converted as perto_json orto_jsonb.

json_build_object('foo', 1, 2, row(3,'bar')){"foo" : 1, "2" : {"f1":3,"f2":"bar"}}

json_object ( [ {key_expression {VALUE | ':' }value_expression [FORMAT JSON [ENCODING UTF8]] }[, ...]] [ {NULL |ABSENT }ON NULL] [ {WITH |WITHOUT }UNIQUE [KEYS]] [RETURNINGdata_type [FORMAT JSON [ENCODING UTF8]]])

Constructs a JSON object of all the key/value pairs given, or an empty object if none are given.key_expression is a scalar expression defining theJSON key, which is converted to thetext type. It cannot beNULL nor can it belong to a type that has a cast to thejson type. IfWITH UNIQUE KEYS is specified, there must not be any duplicatekey_expression. Any pair for which thevalue_expression evaluates toNULL is omitted from the output ifABSENT ON NULL is specified; ifNULL ON NULL is specified or the clause omitted, the key is included with valueNULL.

json_object('code' VALUE 'P123', 'title': 'Jaws'){"code" : "P123", "title" : "Jaws"}

json_object (text[] ) →json

jsonb_object (text[] ) →jsonb

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. All values are converted to JSON strings.

json_object('{a, 1, b, "def", c, 3.5}'){"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 (keystext[],valuestext[] ) →json

jsonb_object (keystext[],valuestext[] ) →jsonb

This form ofjson_object takes keys and values pairwise from separate text arrays. Otherwise it is identical to the one-argument form.

json_object('{a,b}', '{1,2}'){"a": "1", "b": "2"}

json (expression [FORMAT JSON [ENCODING UTF8]] [ {WITH |WITHOUT }UNIQUE [KEYS]] ) →json

Converts a given expression specified astext orbytea string (in UTF8 encoding) into a JSON value. Ifexpression is NULL, anSQL null value is returned. IfWITH UNIQUE is specified, theexpression must not contain any duplicate object keys.

json('{"a":123, "b":[true,"foo"], "a":"bar"}'){"a":123, "b":[true,"foo"], "a":"bar"}

json_scalar (expression )

Converts a given SQL scalar value into a JSON scalar value. If the input is NULL, anSQL null is returned. If the input is number or a boolean value, a corresponding JSON number or boolean value is returned. For any other value, a JSON string is returned.

json_scalar(123.45)123.45

json_scalar(CURRENT_TIMESTAMP)"2022-05-10T10:51:04.62128-04:00"

json_serialize (expression [FORMAT JSON [ENCODING UTF8]] [RETURNINGdata_type [FORMAT JSON [ENCODING UTF8]]] )

Converts an SQL/JSON expression into a character or binary string. Theexpression can be of any JSON type, any character string type, orbytea in UTF8 encoding. The returned type used in RETURNING can be any character string type orbytea. The default istext.

json_serialize('{ "a" : 1 } ' RETURNING bytea)\x7b20226122203a2031207d20

[a] For example, thehstore extension has a cast fromhstore tojson, so thathstore values converted via the JSON creation functions will be represented as JSON objects, not as primitive string values.


Table 9.48 details SQL/JSON facilities for testing JSON.

Table 9.48. SQL/JSON Testing Functions

Function signature

Description

Example(s)

expressionIS [NOT]JSON [ {VALUE |SCALAR |ARRAY |OBJECT }] [ {WITH |WITHOUT }UNIQUE [KEYS]]

This predicate tests whetherexpression can be parsed as JSON, possibly of a specified type. IfSCALAR orARRAY orOBJECT is specified, the test is whether or not the JSON is of that particular type. IfWITH UNIQUE KEYS is specified, then any object in theexpression is also tested to see if it has duplicate keys.

SELECT js,  js IS JSON "json?",  js IS JSON SCALAR "scalar?",  js IS JSON OBJECT "object?",  js IS JSON ARRAY "array?"FROM (VALUES      ('123'), ('"abc"'), ('{"a": "b"}'), ('[1,2]'),('abc')) foo(js);     js     | json? | scalar? | object? | array?------------+-------+---------+---------+-------- 123        | t     | t       | f       | f "abc"      | t     | t       | f       | f {"a": "b"} | t     | f       | t       | f [1,2]      | t     | f       | f       | t abc        | f     | f       | f       | f

SELECT js,  js IS JSON OBJECT "object?",  js IS JSON ARRAY "array?",  js IS JSON ARRAY WITH UNIQUE KEYS "array w. UK?",  js IS JSON ARRAY WITHOUT UNIQUE KEYS "array w/o UK?"FROM (VALUES ('[{"a":"1"}, {"b":"2","b":"3"}]')) foo(js);-[ RECORD 1 ]-+--------------------js            | [{"a":"1"},        +              |  {"b":"2","b":"3"}]object?       | farray?        | tarray w. UK?  | farray w/o UK? | t


Table 9.49 shows the functions that are available for processingjson andjsonb values.

Table 9.49. JSON Processing Functions

Function

Description

Example(s)

json_array_elements (json ) →setof json

jsonb_array_elements (jsonb ) →setof jsonb

Expands the top-level JSON array into a set of JSON values.

select * from json_array_elements('[1,true, [2,false]]')

   value----------- 1 true [2,false]

json_array_elements_text (json ) →setof text

jsonb_array_elements_text (jsonb ) →setof text

Expands the top-level JSON array into a set oftext values.

select * from json_array_elements_text('["foo", "bar"]')

   value----------- foo bar

json_array_length (json ) →integer

jsonb_array_length (jsonb ) →integer

Returns the number of elements in the top-level JSON array.

json_array_length('[1,2,3,{"f1":1,"f2":[5,6]},4]')5

jsonb_array_length('[]')0

json_each (json ) →setof record (keytext,valuejson )

jsonb_each (jsonb ) →setof record (keytext,valuejsonb )

Expands the top-level JSON object into a set of key/value pairs.

select * from json_each('{"a":"foo", "b":"bar"}')

 key | value-----+------- a   | "foo" b   | "bar"

json_each_text (json ) →setof record (keytext,valuetext )

jsonb_each_text (jsonb ) →setof record (keytext,valuetext )

Expands the top-level JSON object into a set of key/value pairs. The returnedvalues will be of typetext.

select * from json_each_text('{"a":"foo", "b":"bar"}')

 key | value-----+------- a   | foo b   | bar

json_extract_path (from_jsonjson,VARIADICpath_elemstext[] ) →json

jsonb_extract_path (from_jsonjsonb,VARIADICpath_elemstext[] ) →jsonb

Extracts JSON sub-object at the specified path. (This is functionally equivalent to the#> operator, but writing the path out as a variadic list can be more convenient in some cases.)

json_extract_path('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6')"foo"

json_extract_path_text (from_jsonjson,VARIADICpath_elemstext[] ) →text

jsonb_extract_path_text (from_jsonjsonb,VARIADICpath_elemstext[] ) →text

Extracts JSON sub-object at the specified path astext. (This is functionally equivalent to the#>> operator.)

json_extract_path_text('{"f2":{"f3":1},"f4":{"f5":99,"f6":"foo"}}', 'f4', 'f6')foo

json_object_keys (json ) →setof text

jsonb_object_keys (jsonb ) →setof text

Returns the set of keys in the top-level JSON object.

select * from json_object_keys('{"f1":"abc","f2":{"f3":"a", "f4":"b"}}')

 json_object_keys------------------ f1 f2

json_populate_record (baseanyelement,from_jsonjson ) →anyelement

jsonb_populate_record (baseanyelement,from_jsonjsonb ) →anyelement

Expands the top-level JSON object to a row having the composite type of thebase argument. The JSON object is scanned for fields whose names match column names of the output row type, and their values are inserted into those columns of the output. (Fields that do not correspond to any output column name are ignored.) In typical use, the value ofbase is justNULL, which means that any output columns that do not match any object field will be filled with nulls. However, ifbase isn'tNULL then the values it contains will be used for unmatched columns.

To convert a JSON value to the SQL type of an output column, the following rules are applied in sequence:

  • A JSON null value is converted to an SQL null in all cases.

  • If the output column is of typejson orjsonb, the JSON value is just reproduced exactly.

  • If the output column is a composite (row) type, and the JSON value is a JSON object, the fields of the object are converted to columns of the output row type by recursive application of these rules.

  • Likewise, if the output column is an array type and the JSON value is a JSON array, the elements of the JSON array are converted to elements of the output array by recursive application of these rules.

  • Otherwise, if the JSON value is a string, the contents of the string are fed to the input conversion function for the column's data type.

  • Otherwise, the ordinary text representation of the JSON value is fed to the input conversion function for the column's data type.

While the example below uses a constant JSON value, typical use would be to reference ajson orjsonb column laterally from another table in the query'sFROM clause. Writingjson_populate_record in theFROM clause is good practice, since all of the extracted columns are available for use without duplicate function calls.

create type subrowtype as (d int, e text);create type myrowtype as (a int, b text[], c subrowtype);

select * from json_populate_record(null::myrowtype, '{"a": 1, "b": ["2", "a b"], "c": {"d": 4, "e": "a b c"}, "x": "foo"}')

 a |   b       |      c---+-----------+------------- 1 | {2,"a b"} | (4,"a b c")

jsonb_populate_record_valid (baseanyelement,from_jsonjson ) →boolean

Function for testingjsonb_populate_record. Returnstrue if the inputjsonb_populate_record would finish without an error for the given input JSON object; that is, it's valid input,false otherwise.

create type jsb_char2 as (a char(2));

select jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aaa"}');

 jsonb_populate_record_valid----------------------------- f(1 row)

select * from jsonb_populate_record(NULL::jsb_char2, '{"a": "aaa"}') q;

ERROR:  value too long for type character(2)

select jsonb_populate_record_valid(NULL::jsb_char2, '{"a": "aa"}');

 jsonb_populate_record_valid----------------------------- t(1 row)

select * from jsonb_populate_record(NULL::jsb_char2, '{"a": "aa"}') q;

 a---- aa(1 row)

json_populate_recordset (baseanyelement,from_jsonjson ) →setof anyelement

jsonb_populate_recordset (baseanyelement,from_jsonjsonb ) →setof anyelement

Expands the top-level JSON array of objects to a set of rows having the composite type of thebase argument. Each element of the JSON array is processed as described above forjson[b]_populate_record.

create type twoints as (a int, b int);

select * from json_populate_recordset(null::twoints, '[{"a":1,"b":2}, {"a":3,"b":4}]')

 a | b---+--- 1 | 2 3 | 4

json_to_record (json ) →record

jsonb_to_record (jsonb ) →record

Expands the top-level JSON object to a row having the composite type defined by anAS clause. (As with all functions returningrecord, the calling query must explicitly define the structure of the record with anAS clause.) The output record is filled from fields of the JSON object, in the same way as described above forjson[b]_populate_record. Since there is no input record value, unmatched columns are always filled with nulls.

create type myrowtype as (a int, b text);

select * from json_to_record('{"a":1,"b":[1,2,3],"c":[1,2,3],"e":"bar","r": {"a": 123, "b": "a b c"}}') as x(a int, b text, c int[], d text, r myrowtype)

 a |    b    |    c    | d |       r---+---------+---------+---+--------------- 1 | [1,2,3] | {1,2,3} |   | (123,"a b c")

json_to_recordset (json ) →setof record

jsonb_to_recordset (jsonb ) →setof record

Expands the top-level JSON array of objects to a set of rows having the composite type defined by anAS clause. (As with all functions returningrecord, the calling query must explicitly define the structure of the record with anAS clause.) Each element of the JSON array is processed as described above forjson[b]_populate_record.

select * from json_to_recordset('[{"a":1,"b":"foo"}, {"a":"2","c":"bar"}]') as x(a int, b text)

 a |  b---+----- 1 | foo 2 |

jsonb_set (targetjsonb,pathtext[],new_valuejsonb [,create_if_missingboolean] ) →jsonb

Returnstarget with the item designated bypath replaced bynew_value, or withnew_value added ifcreate_if_missing is true (which is the default) and the item designated bypath does not exist. All earlier steps in the path must exist, or thetarget is returned unchanged. As with the path oriented operators, negative integers that appear in thepath count from the end of JSON arrays. If the last path step is an array index that is out of range, andcreate_if_missing is true, the new value is added at the beginning of the array if the index is negative, or at the end of the array if it is positive.

jsonb_set('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', '[2,3,4]', false)[{"f1": [2, 3, 4], "f2": null}, 2, null, 3]

jsonb_set('[{"f1":1,"f2":null},2]', '{0,f3}', '[2,3,4]')[{"f1": 1, "f2": null, "f3": [2, 3, 4]}, 2]

jsonb_set_lax (targetjsonb,pathtext[],new_valuejsonb [,create_if_missingboolean [,null_value_treatmenttext]] ) →jsonb

Ifnew_value is notNULL, behaves identically tojsonb_set. Otherwise behaves according to the value ofnull_value_treatment which must be one of'raise_exception','use_json_null','delete_key', or'return_target'. The default is'use_json_null'.

jsonb_set_lax('[{"f1":1,"f2":null},2,null,3]', '{0,f1}', null)[{"f1": null, "f2": null}, 2, null, 3]

jsonb_set_lax('[{"f1":99,"f2":null},2]', '{0,f3}', null, true, 'return_target')[{"f1": 99, "f2": null}, 2]

jsonb_insert (targetjsonb,pathtext[],new_valuejsonb [,insert_afterboolean] ) →jsonb

Returnstarget withnew_value inserted. If the item designated by thepath is an array element,new_value will be inserted before that item ifinsert_after is false (which is the default), or after it ifinsert_after is true. If the item designated by thepath is an object field,new_value will be inserted only if the object does not already contain that key. All earlier steps in the path must exist, or thetarget is returned unchanged. As with the path oriented operators, negative integers that appear in thepath count from the end of JSON arrays. If the last path step is an array index that is out of range, the new value is added at the beginning of the array if the index is negative, or at the end of the array if it is positive.

jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"'){"a": [0, "new_value", 1, 2]}

jsonb_insert('{"a": [0,1,2]}', '{a, 1}', '"new_value"', true){"a": [0, 1, "new_value", 2]}

json_strip_nulls (json ) →json

jsonb_strip_nulls (jsonb ) →jsonb

Deletes all object fields that have null values from the given JSON value, recursively. Null values that are not object fields are untouched.

json_strip_nulls('[{"f1":1, "f2":null}, 2, null, 3]')[{"f1":1},2,null,3]

jsonb_path_exists (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →boolean

Checks whether the JSON path returns any item for the specified JSON value. (This is useful only with SQL-standard JSON path expressions, notpredicate check expressions, since those always return a value.) If thevars argument is specified, it must be a JSON object, and its fields provide named values to be substituted into thejsonpath expression. If thesilent argument is specified and istrue, the function suppresses the same errors as the@? and@@ operators do.

jsonb_path_exists('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}')t

jsonb_path_match (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →boolean

Returns the SQL boolean result of a JSON path predicate check for the specified JSON value. (This is useful only withpredicate check expressions, not SQL-standard JSON path expressions, since it will either fail or returnNULL if the path result is not a single boolean value.) The optionalvars andsilent arguments act the same as forjsonb_path_exists.

jsonb_path_match('{"a":[1,2,3,4,5]}', 'exists($.a[*] ? (@ >= $min && @ <= $max))', '{"min":2, "max":4}')t

jsonb_path_query (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →setof jsonb

Returns all JSON items returned by the JSON path for the specified JSON value. For SQL-standard JSON path expressions it returns the JSON values selected fromtarget. Forpredicate check expressions it returns the result of the predicate check:true,false, ornull. The optionalvars andsilent arguments act the same as forjsonb_path_exists.

select * from jsonb_path_query('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}')

 jsonb_path_query------------------ 2 3 4

jsonb_path_query_array (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →jsonb

Returns all JSON items returned by the JSON path for the specified JSON value, as a JSON array. The parameters are the same as forjsonb_path_query.

jsonb_path_query_array('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}')[2, 3, 4]

jsonb_path_query_first (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →jsonb

Returns the first JSON item returned by the JSON path for the specified JSON value, orNULL if there are no results. The parameters are the same as forjsonb_path_query.

jsonb_path_query_first('{"a":[1,2,3,4,5]}', '$.a[*] ? (@ >= $min && @ <= $max)', '{"min":2, "max":4}')2

jsonb_path_exists_tz (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →boolean

jsonb_path_match_tz (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →boolean

jsonb_path_query_tz (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →setof jsonb

jsonb_path_query_array_tz (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →jsonb

jsonb_path_query_first_tz (targetjsonb,pathjsonpath [,varsjsonb [,silentboolean]] ) →jsonb

These functions act like their counterparts described above without the_tz suffix, except that these functions support comparisons of date/time values that require timezone-aware conversions. The example below requires interpretation of the date-only value2015-08-02 as a timestamp with time zone, so the result depends on the currentTimeZone setting. Due to this dependency, these functions are marked as stable, which means these functions cannot be used in indexes. Their counterparts are immutable, and so can be used in indexes; but they will throw errors if asked to make such comparisons.

jsonb_path_exists_tz('["2015-08-01 12:00:00-05"]', '$[*] ? (@.datetime() < "2015-08-02".datetime())')t

jsonb_pretty (jsonb ) →text

Converts the given JSON value to pretty-printed, indented text.

jsonb_pretty('[{"f1":1,"f2":null}, 2]')

[    {        "f1": 1,        "f2": null    },    2]

json_typeof (json ) →text

jsonb_typeof (jsonb ) →text

Returns the type of the top-level JSON value as a text string. Possible types areobject,array,string,number,boolean, andnull. (Thenull result should not be confused with an SQL NULL; see the examples.)

json_typeof('-123.4')number

json_typeof('null'::json)null

json_typeof(NULL::json) IS NULLt


9.16.2. The SQL/JSON Path Language#

SQL/JSON path expressions specify item(s) to be retrieved from a JSON value, similarly to XPath expressions used for access to XML content. InPostgreSQL, path expressions are implemented as thejsonpath data type and can use any elements described inSection 8.14.7.

JSON query functions and operators pass the provided path expression to thepath engine for evaluation. If the expression matches the queried JSON data, the corresponding JSON item, or set of items, is returned. If there is no match, the result will beNULL,false, or an error, depending on the function. Path expressions are written in the SQL/JSON path language and can include arithmetic expressions and functions.

A path expression consists of a sequence of elements allowed by thejsonpath data type. The path expression is normally evaluated from left to right, but you can use parentheses to change the order of operations. If the evaluation is successful, a sequence of JSON items is produced, and the evaluation result is returned to the JSON query function that completes the specified computation.

To refer to the JSON value being queried (thecontext item), use the$ variable in the path expression. The first element of a path must always be$. It can be followed by one or moreaccessor operators, which go down the JSON structure level by level to retrieve sub-items of the context item. Each accessor operator acts on the result(s) of the previous evaluation step, producing zero, one, or more output items from each input item.

For example, suppose you have some JSON data from a GPS tracker that you would like to parse, such as:

SELECT '{  "track": {    "segments": [      {        "location":   [ 47.763, 13.4034 ],        "start time": "2018-10-14 10:05:14",        "HR": 73      },      {        "location":   [ 47.706, 13.2635 ],        "start time": "2018-10-14 10:39:21",        "HR": 135      }    ]  }}' AS json \gset

(The above example can be copied-and-pasted intopsql to set things up for the following examples. Thenpsql will expand:'json' into a suitably-quoted string constant containing the JSON value.)

To retrieve the available track segments, you need to use the.key accessor operator to descend through surrounding JSON objects, for example:

=>select jsonb_path_query(:'json', '$.track.segments');                                                                         jsonb_path_query-----------------------------------------------------------​-----------------------------------------------------------​--------------------------------------------- [{"HR": 73, "location": [47.763, 13.4034], "start time": "2018-10-14 10:05:14"}, {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"}]

To retrieve the contents of an array, you typically use the[*] operator. The following example will return the location coordinates for all the available track segments:

=>select jsonb_path_query(:'json', '$.track.segments[*].location'); jsonb_path_query------------------- [47.763, 13.4034] [47.706, 13.2635]

Here we started with the whole JSON input value ($), then the.track accessor selected the JSON object associated with the"track" object key, then the.segments accessor selected the JSON array associated with the"segments" key within that object, then the[*] accessor selected each element of that array (producing a series of items), then the.location accessor selected the JSON array associated with the"location" key within each of those objects. In this example, each of those objects had a"location" key; but if any of them did not, the.location accessor would have simply produced no output for that input item.

To return the coordinates of the first segment only, you can specify the corresponding subscript in the[] accessor operator. Recall that JSON array indexes are 0-relative:

=>select jsonb_path_query(:'json', '$.track.segments[0].location'); jsonb_path_query------------------- [47.763, 13.4034]

The result of each path evaluation step can be processed by one or more of thejsonpath operators and methods listed inSection 9.16.2.3. Each method name must be preceded by a dot. For example, you can get the size of an array:

=>select jsonb_path_query(:'json', '$.track.segments.size()'); jsonb_path_query------------------ 2

More examples of usingjsonpath operators and methods within path expressions appear below inSection 9.16.2.3.

A path can also containfilter expressions that work similarly to theWHERE clause in SQL. A filter expression begins with a question mark and provides a condition in parentheses:

? (condition)

Filter expressions must be written just after the path evaluation step to which they should apply. The result of that step is filtered to include only those items that satisfy the provided condition. SQL/JSON defines three-valued logic, so the condition can producetrue,false, orunknown. Theunknown value plays the same role as SQLNULL and can be tested for with theis unknown predicate. Further path evaluation steps use only those items for which the filter expression returnedtrue.

The functions and operators that can be used in filter expressions are listed inTable 9.51. Within a filter expression, the@ variable denotes the value being considered (i.e., one result of the preceding path step). You can write accessor operators after@ to retrieve component items.

For example, suppose you would like to retrieve all heart rate values higher than 130. You can achieve this as follows:

=>select jsonb_path_query(:'json', '$.track.segments[*].HR ? (@ > 130)'); jsonb_path_query------------------ 135

To get the start times of segments with such values, you have to filter out irrelevant segments before selecting the start times, so the filter expression is applied to the previous step, and the path used in the condition is different:

=>select jsonb_path_query(:'json', '$.track.segments[*] ? (@.HR > 130)."start time"');   jsonb_path_query----------------------- "2018-10-14 10:39:21"

You can use several filter expressions in sequence, if required. The following example selects start times of all segments that contain locations with relevant coordinates and high heart rate values:

=>select jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] < 13.4) ? (@.HR > 130)."start time"');   jsonb_path_query----------------------- "2018-10-14 10:39:21"

Using filter expressions at different nesting levels is also allowed. The following example first filters all segments by location, and then returns high heart rate values for these segments, if available:

=>select jsonb_path_query(:'json', '$.track.segments[*] ? (@.location[1] < 13.4).HR ? (@ > 130)'); jsonb_path_query------------------ 135

You can also nest filter expressions within each other. This example returns the size of the track if it contains any segments with high heart rate values, or an empty sequence otherwise:

=>select jsonb_path_query(:'json', '$.track ? (exists(@.segments[*] ? (@.HR > 130))).segments.size()'); jsonb_path_query------------------ 2

9.16.2.1. Deviations from the SQL Standard#

PostgreSQL's implementation of the SQL/JSON path language has the following deviations from the SQL/JSON standard.

9.16.2.1.1. Boolean Predicate Check Expressions#

As an extension to the SQL standard, aPostgreSQL path expression can be a Boolean predicate, whereas the SQL standard allows predicates only within filters. While SQL-standard path expressions return the relevant element(s) of the queried JSON value, predicate check expressions return the single three-valuedjsonb result of the predicate:true,false, ornull. For example, we could write this SQL-standard filter expression:

=>select jsonb_path_query(:'json', '$.track.segments ?(@[*].HR > 130)');                                jsonb_path_query-----------------------------------------------------------​---------------------- {"HR": 135, "location": [47.706, 13.2635], "start time": "2018-10-14 10:39:21"}

The similar predicate check expression simply returnstrue, indicating that a match exists:

=>select jsonb_path_query(:'json', '$.track.segments[*].HR > 130'); jsonb_path_query------------------ true

Note

Predicate check expressions are required in the@@ operator (and thejsonb_path_match function), and should not be used with the@? operator (or thejsonb_path_exists function).

9.16.2.1.2. Regular Expression Interpretation#

There are minor differences in the interpretation of regular expression patterns used inlike_regex filters, as described inSection 9.16.2.4.

9.16.2.2. Strict and Lax Modes#

When you query JSON data, the path expression may not match the actual JSON data structure. An attempt to access a non-existent member of an object or element of an array is defined as a structural error. SQL/JSON path expressions have two modes of handling structural errors:

  • lax (default) — the path engine implicitly adapts the queried data to the specified path. Any structural errors that cannot be fixed as described below are suppressed, producing no match.

  • strict — if a structural error occurs, an error is raised.

Lax mode facilitates matching of a JSON document and path expression when the JSON data does not conform to the expected schema. If an operand does not match the requirements of a particular operation, it can be automatically wrapped as an SQL/JSON array, or unwrapped by converting its elements into an SQL/JSON sequence before performing the operation. Also, comparison operators automatically unwrap their operands in lax mode, so you can compare SQL/JSON arrays out-of-the-box. An array of size 1 is considered equal to its sole element. Automatic unwrapping is not performed when:

  • The path expression containstype() orsize() methods that return the type and the number of elements in the array, respectively.

  • The queried JSON data contain nested arrays. In this case, only the outermost array is unwrapped, while all the inner arrays remain unchanged. Thus, implicit unwrapping can only go one level down within each path evaluation step.

For example, when querying the GPS data listed above, you can abstract from the fact that it stores an array of segments when using lax mode:

=>select jsonb_path_query(:'json', 'lax $.track.segments.location'); jsonb_path_query------------------- [47.763, 13.4034] [47.706, 13.2635]

In strict mode, the specified path must exactly match the structure of the queried JSON document, so using this path expression will cause an error:

=>select jsonb_path_query(:'json', 'strict $.track.segments.location');ERROR:  jsonpath member accessor can only be applied to an object

To get the same result as in lax mode, you have to explicitly unwrap thesegments array:

=>select jsonb_path_query(:'json', 'strict $.track.segments[*].location'); jsonb_path_query------------------- [47.763, 13.4034] [47.706, 13.2635]

The unwrapping behavior of lax mode can lead to surprising results. For instance, the following query using the.** accessor selects everyHR value twice:

=>select jsonb_path_query(:'json', 'lax $.**.HR'); jsonb_path_query------------------ 73 135 73 135

This happens because the.** accessor selects both thesegments array and each of its elements, while the.HR accessor automatically unwraps arrays when using lax mode. To avoid surprising results, we recommend using the.** accessor only in strict mode. The following query selects eachHR value just once:

=>select jsonb_path_query(:'json', 'strict $.**.HR'); jsonb_path_query------------------ 73 135

The unwrapping of arrays can also lead to unexpected results. Consider this example, which selects all thelocation arrays:

=>select jsonb_path_query(:'json', 'lax $.track.segments[*].location'); jsonb_path_query------------------- [47.763, 13.4034] [47.706, 13.2635](2 rows)

As expected it returns the full arrays. But applying a filter expression causes the arrays to be unwrapped to evaluate each item, returning only the items that match the expression:

=>select jsonb_path_query(:'json', 'lax $.track.segments[*].location ?(@[*] > 15)'); jsonb_path_query------------------ 47.763 47.706(2 rows)

This despite the fact that the full arrays are selected by the path expression. Use strict mode to restore selecting the arrays:

=>select jsonb_path_query(:'json', 'strict $.track.segments[*].location ?(@[*] > 15)'); jsonb_path_query------------------- [47.763, 13.4034] [47.706, 13.2635](2 rows)

9.16.2.3. SQL/JSON Path Operators and Methods#

Table 9.50 shows the operators and methods available injsonpath. Note that while the unary operators and methods can be applied to multiple values resulting from a preceding path step, the binary operators (addition etc.) can only be applied to single values. In lax mode, methods applied to an array will be executed for each value in the array. The exceptions are.type() and.size(), which apply to the array itself.

Table 9.50. jsonpath Operators and Methods

Operator/Method

Description

Example(s)

number+numbernumber

Addition

jsonb_path_query('[2]', '$[0] + 3')5

+numbernumber

Unary plus (no operation); unlike addition, this can iterate over multiple values

jsonb_path_query_array('{"x": [2,3,4]}', '+ $.x')[2, 3, 4]

number-numbernumber

Subtraction

jsonb_path_query('[2]', '7 - $[0]')5

-numbernumber

Negation; unlike subtraction, this can iterate over multiple values

jsonb_path_query_array('{"x": [2,3,4]}', '- $.x')[-2, -3, -4]

number*numbernumber

Multiplication

jsonb_path_query('[4]', '2 * $[0]')8

number/numbernumber

Division

jsonb_path_query('[8.5]', '$[0] / 2')4.2500000000000000

number%numbernumber

Modulo (remainder)

jsonb_path_query('[32]', '$[0] % 10')2

value.type()string

Type of the JSON item (seejson_typeof)

jsonb_path_query_array('[1, "2", {}]', '$[*].type()')["number", "string", "object"]

value.size()number

Size of the JSON item (number of array elements, or 1 if not an array)

jsonb_path_query('{"m": [11, 15]}', '$.m.size()')2

value.boolean()boolean

Boolean value converted from a JSON boolean, number, or string

jsonb_path_query_array('[1, "yes", false]', '$[*].boolean()')[true, true, false]

value.string()string

String value converted from a JSON boolean, number, string, or datetime

jsonb_path_query_array('[1.23, "xyz", false]', '$[*].string()')["1.23", "xyz", "false"]

jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp().string()')"2023-08-15T12:34:56"

value.double()number

Approximate floating-point number converted from a JSON number or string

jsonb_path_query('{"len": "1.9"}', '$.len.double() * 2')3.8

number.ceiling()number

Nearest integer greater than or equal to the given number

jsonb_path_query('{"h": 1.3}', '$.h.ceiling()')2

number.floor()number

Nearest integer less than or equal to the given number

jsonb_path_query('{"h": 1.7}', '$.h.floor()')1

number.abs()number

Absolute value of the given number

jsonb_path_query('{"z": -0.3}', '$.z.abs()')0.3

value.bigint()bigint

Big integer value converted from a JSON number or string

jsonb_path_query('{"len": "9876543219"}', '$.len.bigint()')9876543219

value.decimal( [precision [ ,scale ] ] )decimal

Rounded decimal value converted from a JSON number or string (precision andscale must be integer values)

jsonb_path_query('1234.5678', '$.decimal(6, 2)')1234.57

value.integer()integer

Integer value converted from a JSON number or string

jsonb_path_query('{"len": "12345"}', '$.len.integer()')12345

value.number()numeric

Numeric value converted from a JSON number or string

jsonb_path_query('{"len": "123.45"}', '$.len.number()')123.45

string.datetime()datetime_type (see note)

Date/time value converted from a string

jsonb_path_query('["2015-8-1", "2015-08-12"]', '$[*] ? (@.datetime() < "2015-08-2".datetime())')"2015-8-1"

string.datetime(template)datetime_type (see note)

Date/time value converted from a string using the specifiedto_timestamp template

jsonb_path_query_array('["12:30", "18:40"]', '$[*].datetime("HH24:MI")')["12:30:00", "18:40:00"]

string.date()date

Date value converted from a string

jsonb_path_query('"2023-08-15"', '$.date()')"2023-08-15"

string.time()time without time zone

Time without time zone value converted from a string

jsonb_path_query('"12:34:56"', '$.time()')"12:34:56"

string.time(precision)time without time zone

Time without time zone value converted from a string, with fractional seconds adjusted to the given precision

jsonb_path_query('"12:34:56.789"', '$.time(2)')"12:34:56.79"

string.time_tz()time with time zone

Time with time zone value converted from a string

jsonb_path_query('"12:34:56 +05:30"', '$.time_tz()')"12:34:56+05:30"

string.time_tz(precision)time with time zone

Time with time zone value converted from a string, with fractional seconds adjusted to the given precision

jsonb_path_query('"12:34:56.789 +05:30"', '$.time_tz(2)')"12:34:56.79+05:30"

string.timestamp()timestamp without time zone

Timestamp without time zone value converted from a string

jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp()')"2023-08-15T12:34:56"

string.timestamp(precision)timestamp without time zone

Timestamp without time zone value converted from a string, with fractional seconds adjusted to the given precision

jsonb_path_query('"2023-08-15 12:34:56.789"', '$.timestamp(2)')"2023-08-15T12:34:56.79"

string.timestamp_tz()timestamp with time zone

Timestamp with time zone value converted from a string

jsonb_path_query('"2023-08-15 12:34:56 +05:30"', '$.timestamp_tz()')"2023-08-15T12:34:56+05:30"

string.timestamp_tz(precision)timestamp with time zone

Timestamp with time zone value converted from a string, with fractional seconds adjusted to the given precision

jsonb_path_query('"2023-08-15 12:34:56.789 +05:30"', '$.timestamp_tz(2)')"2023-08-15T12:34:56.79+05:30"

object.keyvalue()array

The object's key-value pairs, represented as an array of objects containing three fields:"key","value", and"id";"id" is a unique identifier of the object the key-value pair belongs to

jsonb_path_query_array('{"x": "20", "y": 32}', '$.keyvalue()')[{"id": 0, "key": "x", "value": "20"}, {"id": 0, "key": "y", "value": 32}]


Note

The result type of thedatetime() anddatetime(template) methods can bedate,timetz,time,timestamptz, ortimestamp. Both methods determine their result type dynamically.

Thedatetime() method sequentially tries to match its input string to the ISO formats fordate,timetz,time,timestamptz, andtimestamp. It stops on the first matching format and emits the corresponding data type.

Thedatetime(template) method determines the result type according to the fields used in the provided template string.

Thedatetime() anddatetime(template) methods use the same parsing rules as theto_timestamp SQL function does (seeSection 9.8), with three exceptions. First, these methods don't allow unmatched template patterns. Second, only the following separators are allowed in the template string: minus sign, period, solidus (slash), comma, apostrophe, semicolon, colon and space. Third, separators in the template string must exactly match the input string.

If different date/time types need to be compared, an implicit cast is applied. Adate value can be cast totimestamp ortimestamptz,timestamp can be cast totimestamptz, andtime totimetz. However, all but the first of these conversions depend on the currentTimeZone setting, and thus can only be performed within timezone-awarejsonpath functions. Similarly, other date/time-related methods that convert strings to date/time types also do this casting, which may involve the currentTimeZone setting. Therefore, these conversions can also only be performed within timezone-awarejsonpath functions.

Table 9.51 shows the available filter expression elements.

Table 9.51. jsonpath Filter Expression Elements

Predicate/Value

Description

Example(s)

value==valueboolean

Equality comparison (this, and the other comparison operators, work on all JSON scalar values)

jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == 1)')[1, 1]

jsonb_path_query_array('[1, "a", 1, 3]', '$[*] ? (@ == "a")')["a"]

value!=valueboolean

value<>valueboolean

Non-equality comparison

jsonb_path_query_array('[1, 2, 1, 3]', '$[*] ? (@ != 1)')[2, 3]

jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ <> "b")')["a", "c"]

value<valueboolean

Less-than comparison

jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ < 2)')[1]

value<=valueboolean

Less-than-or-equal-to comparison

jsonb_path_query_array('["a", "b", "c"]', '$[*] ? (@ <= "b")')["a", "b"]

value>valueboolean

Greater-than comparison

jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ > 2)')[3]

value>=valueboolean

Greater-than-or-equal-to comparison

jsonb_path_query_array('[1, 2, 3]', '$[*] ? (@ >= 2)')[2, 3]

trueboolean

JSON constanttrue

jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == true)'){"name": "Chris", "parent": true}

falseboolean

JSON constantfalse

jsonb_path_query('[{"name": "John", "parent": false}, {"name": "Chris", "parent": true}]', '$[*] ? (@.parent == false)'){"name": "John", "parent": false}

nullvalue

JSON constantnull (note that, unlike in SQL, comparison tonull works normally)

jsonb_path_query('[{"name": "Mary", "job": null}, {"name": "Michael", "job": "driver"}]', '$[*] ? (@.job == null) .name')"Mary"

boolean&&booleanboolean

Boolean AND

jsonb_path_query('[1, 3, 7]', '$[*] ? (@ > 1 && @ < 5)')3

boolean||booleanboolean

Boolean OR

jsonb_path_query('[1, 3, 7]', '$[*] ? (@ < 1 || @ > 5)')7

!booleanboolean

Boolean NOT

jsonb_path_query('[1, 3, 7]', '$[*] ? (!(@ < 5))')7

booleanis unknownboolean

Tests whether a Boolean condition isunknown.

jsonb_path_query('[-1, 2, 7, "foo"]', '$[*] ? ((@ > 0) is unknown)')"foo"

stringlike_regexstring [flagstring] →boolean

Tests whether the first operand matches the regular expression given by the second operand, optionally with modifications described by a string offlag characters (seeSection 9.16.2.4).

jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c")')["abc", "abdacb"]

jsonb_path_query_array('["abc", "abd", "aBdC", "abdacb", "babc"]', '$[*] ? (@ like_regex "^ab.*c" flag "i")')["abc", "aBdC", "abdacb"]

stringstarts withstringboolean

Tests whether the second operand is an initial substring of the first operand.

jsonb_path_query('["John Smith", "Mary Stone", "Bob Johnson"]', '$[*] ? (@ starts with "John")')"John Smith"

exists(path_expression)boolean

Tests whether a path expression matches at least one SQL/JSON item. Returnsunknown if the path expression would result in an error; the second example uses this to avoid a no-such-key error in strict mode.

jsonb_path_query('{"x": [1, 2], "y": [2, 4]}', 'strict $.* ? (exists (@ ? (@[*] > 2)))')[2, 4]

jsonb_path_query_array('{"value": 41}', 'strict $ ? (exists (@.name)) .name')[]


9.16.2.4. SQL/JSON Regular Expressions#

SQL/JSON path expressions allow matching text to a regular expression with thelike_regex filter. For example, the following SQL/JSON path query would case-insensitively match all strings in an array that start with an English vowel:

$[*] ? (@ like_regex "^[aeiou]" flag "i")

The optionalflag string may include one or more of the charactersi for case-insensitive match,m to allow^ and$ to match at newlines,s to allow. to match a newline, andq to quote the whole pattern (reducing the behavior to a simple substring match).

The SQL/JSON standard borrows its definition for regular expressions from theLIKE_REGEX operator, which in turn uses the XQuery standard. PostgreSQL does not currently support theLIKE_REGEX operator. Therefore, thelike_regex filter is implemented using the POSIX regular expression engine described inSection 9.7.3. This leads to various minor discrepancies from standard SQL/JSON behavior, which are cataloged inSection 9.7.3.8. Note, however, that the flag-letter incompatibilities described there do not apply to SQL/JSON, as it translates the XQuery flag letters to match what the POSIX engine expects.

Keep in mind that the pattern argument oflike_regex is a JSON path string literal, written according to the rules given inSection 8.14.7. This means in particular that any backslashes you want to use in the regular expression must be doubled. For example, to match string values of the root document that contain only digits:

$.* ? (@ like_regex "^\\d+$")

9.16.3. SQL/JSON Query Functions#

SQL/JSON functionsJSON_EXISTS(),JSON_QUERY(), andJSON_VALUE() described inTable 9.52 can be used to query JSON documents. Each of these functions apply apath_expression (an SQL/JSON path query) to acontext_item (the document). SeeSection 9.16.2 for more details on what thepath_expression can contain. Thepath_expression can also reference variables, whose values are specified with their respective names in thePASSING clause that is supported by each function.context_item can be ajsonb value or a character string that can be successfully cast tojsonb.

Table 9.52. SQL/JSON Query Functions

Function signature

Description

Example(s)

JSON_EXISTS (context_item,path_expression[PASSING {valueASvarname } [, ...]][{TRUE |FALSE | UNKNOWN |ERROR }ON ERROR]) →boolean

  • Returns true if the SQL/JSONpath_expression applied to thecontext_item yields any items, false otherwise.

  • TheON ERROR clause specifies the behavior if an error occurs duringpath_expression evaluation. SpecifyingERROR will cause an error to be thrown with the appropriate message. Other options include returningboolean valuesFALSE orTRUE or the valueUNKNOWN which is actually an SQL NULL. The default when noON ERROR clause is specified is to return theboolean valueFALSE.

Examples:

JSON_EXISTS(jsonb '{"key1": [1,2,3]}', 'strict $.key1[*] ? (@ > $x)' PASSING 2 AS x)t

JSON_EXISTS(jsonb '{"a": [1,2,3]}', 'lax $.a[5]' ERROR ON ERROR)f

JSON_EXISTS(jsonb '{"a": [1,2,3]}', 'strict $.a[5]' ERROR ON ERROR)

ERROR:  jsonpath array subscript is out of bounds

JSON_QUERY (context_item,path_expression[PASSING {valueASvarname } [, ...]][RETURNINGdata_type [FORMAT JSON [ENCODING UTF8]]][ {WITHOUT |WITH {CONDITIONAL | [UNCONDITIONAL] } } [ARRAY]WRAPPER][ {KEEP |OMIT }QUOTES [ON SCALAR STRING]][ {ERROR |NULL |EMPTY { [ARRAY] |OBJECT } |DEFAULTexpression }ON EMPTY][ {ERROR |NULL |EMPTY { [ARRAY] |OBJECT } |DEFAULTexpression }ON ERROR]) →jsonb

  • Returns the result of applying the SQL/JSONpath_expression to thecontext_item.

  • By default, the result is returned as a value of typejsonb, though theRETURNING clause can be used to return as some other type to which it can be successfully coerced.

  • If the path expression may return multiple values, it might be necessary to wrap those values using theWITH WRAPPER clause to make it a valid JSON string, because the default behavior is to not wrap them, as ifWITHOUT WRAPPER were specified. TheWITH WRAPPER clause is by default taken to meanWITH UNCONDITIONAL WRAPPER, which means that even a single result value will be wrapped. To apply the wrapper only when multiple values are present, specifyWITH CONDITIONAL WRAPPER. Getting multiple values in result will be treated as an error ifWITHOUT WRAPPER is specified.

  • If the result is a scalar string, by default, the returned value will be surrounded by quotes, making it a valid JSON value. It can be made explicit by specifyingKEEP QUOTES. Conversely, quotes can be omitted by specifyingOMIT QUOTES. To ensure that the result is a valid JSON value,OMIT QUOTES cannot be specified whenWITH WRAPPER is also specified.

  • TheON EMPTY clause specifies the behavior if evaluatingpath_expression yields an empty set. TheON ERROR clause specifies the behavior if an error occurs when evaluatingpath_expression, when coercing the result value to theRETURNING type, or when evaluating theON EMPTY expression if thepath_expression evaluation returns an empty set.

  • For bothON EMPTY andON ERROR, specifyingERROR will cause an error to be thrown with the appropriate message. Other options include returning an SQL NULL, an empty array (EMPTY [ARRAY]), an empty object (EMPTY OBJECT), or a user-specified expression (DEFAULTexpression) that can be coerced to jsonb or the type specified inRETURNING. The default whenON EMPTY orON ERROR is not specified is to return an SQL NULL value.

Examples:

JSON_QUERY(jsonb '[1,[2,3],null]', 'lax $[*][$off]' PASSING 1 AS off WITH CONDITIONAL WRAPPER)3

JSON_QUERY(jsonb '{"a": "[1, 2]"}', 'lax $.a' OMIT QUOTES)[1, 2]

JSON_QUERY(jsonb '{"a": "[1, 2]"}', 'lax $.a' RETURNING int[] OMIT QUOTES ERROR ON ERROR)

ERROR:  malformed array literal: "[1, 2]"DETAIL:  Missing "]" after array dimensions.

JSON_VALUE (context_item,path_expression[PASSING {valueASvarname } [, ...]][RETURNINGdata_type][ {ERROR |NULL |DEFAULTexpression }ON EMPTY][ {ERROR |NULL |DEFAULTexpression }ON ERROR]) →text

Examples:

JSON_VALUE(jsonb '"123.45"', '$' RETURNING float)123.45

JSON_VALUE(jsonb '"03:04 2015-02-01"', '$.datetime("HH24:MI YYYY-MM-DD")' RETURNING date)2015-02-01

JSON_VALUE(jsonb '[1,2]', 'strict $[$off]' PASSING 1 as off)2

JSON_VALUE(jsonb '[1,2]', 'strict $[*]' DEFAULT 9 ON ERROR)9


Note

Thecontext_item expression is converted tojsonb by an implicit cast if the expression is not already of typejsonb. Note, however, that any parsing errors that occur during that conversion are thrown unconditionally, that is, are not handled according to the (specified or implicit)ON ERROR clause.

Note

JSON_VALUE() returns an SQL NULL ifpath_expression returns a JSONnull, whereasJSON_QUERY() returns the JSONnull as is.

9.16.4. JSON_TABLE#

JSON_TABLE is an SQL/JSON function which queriesJSON data and presents the results as a relational view, which can be accessed as a regular SQL table. You can useJSON_TABLE inside theFROM clause of aSELECT,UPDATE, orDELETE and as data source in aMERGE statement.

Taking JSON data as input,JSON_TABLE uses a JSON path expression to extract a part of the provided data to use as arow pattern for the constructed view. Each SQL/JSON value given by the row pattern serves as source for a separate row in the constructed view.

To split the row pattern into columns,JSON_TABLE provides theCOLUMNS clause that defines the schema of the created view. For each column, a separate JSON path expression can be specified to be evaluated against the row pattern to get an SQL/JSON value that will become the value for the specified column in a given output row.

JSON data stored at a nested level of the row pattern can be extracted using theNESTED PATH clause. EachNESTED PATH clause can be used to generate one or more columns using the data from a nested level of the row pattern. Those columns can be specified using aCOLUMNS clause that looks similar to the top-level COLUMNS clause. Rows constructed from NESTED COLUMNS are calledchild rows and are joined against the row constructed from the columns specified in the parentCOLUMNS clause to get the row in the final view. Child columns themselves may contain aNESTED PATH specification thus allowing to extract data located at arbitrary nesting levels. Columns produced by multipleNESTED PATHs at the same level are considered to besiblings of each other and their rows after joining with the parent row are combined using UNION.

The rows produced byJSON_TABLE are laterally joined to the row that generated them, so you do not have to explicitly join the constructed view with the original table holdingJSON data.

The syntax is:

JSON_TABLE (context_item,path_expression [ ASjson_path_name] [ PASSING {value ASvarname } [, ...]]    COLUMNS (json_table_column [, ...] )    [ {ERROR |EMPTY [ARRAY]}ON ERROR])wherejson_table_column is:name FOR ORDINALITY  |nametype        [ FORMAT JSON [ENCODINGUTF8]]        [ PATHpath_expression]        [ { WITHOUT | WITH { CONDITIONAL | [UNCONDITIONAL] } } [ ARRAY] WRAPPER]        [ { KEEP | OMIT } QUOTES [ ON SCALAR STRING]]        [ { ERROR | NULL | EMPTY { [ARRAY] | OBJECT } | DEFAULTexpression } ON EMPTY]        [ { ERROR | NULL | EMPTY { [ARRAY] | OBJECT } | DEFAULTexpression } ON ERROR]  |nametype EXISTS [ PATHpath_expression]        [ { ERROR | TRUE | FALSE | UNKNOWN } ON ERROR]  | NESTED [ PATH]path_expression [ ASjson_path_name] COLUMNS (json_table_column [, ...] )

Each syntax element is described below in more detail.

context_item,path_expression [ASjson_path_name] [PASSING {valueASvarname } [, ...]]

Thecontext_item specifies the input document to query, thepath_expression is an SQL/JSON path expression defining the query, andjson_path_name is an optional name for thepath_expression. The optionalPASSING clause provides data values for the variables mentioned in thepath_expression. The result of the input data evaluation using the aforementioned elements is called therow pattern, which is used as the source for row values in the constructed view.

COLUMNS (json_table_column [, ...] )

TheCOLUMNS clause defining the schema of the constructed view. In this clause, you can specify each column to be filled with an SQL/JSON value obtained by applying a JSON path expression against the row pattern.json_table_column has the following variants:

nameFOR ORDINALITY

Adds an ordinality column that provides sequential row numbering starting from 1. EachNESTED PATH (see below) gets its own counter for any nested ordinality columns.

nametype [FORMAT JSON [ENCODINGUTF8]] [PATHpath_expression]

Inserts an SQL/JSON value obtained by applyingpath_expression against the row pattern into the view's output row after coercing it to specifiedtype.

SpecifyingFORMAT JSON makes it explicit that you expect the value to be a validjson object. It only makes sense to specifyFORMAT JSON iftype is one ofbpchar,bytea,character varying,name,json,jsonb,text, or a domain over these types.

Optionally, you can specifyWRAPPER andQUOTES clauses to format the output. Note that specifyingOMIT QUOTES overridesFORMAT JSON if also specified, because unquoted literals do not constitute validjson values.

Optionally, you can useON EMPTY andON ERROR clauses to specify whether to throw the error or return the specified value when the result of JSON path evaluation is empty and when an error occurs during JSON path evaluation or when coercing the SQL/JSON value to the specified type, respectively. The default for both is to return aNULL value.

nametypeEXISTS [PATHpath_expression]

Inserts a boolean value obtained by applyingpath_expression against the row pattern into the view's output row after coercing it to specifiedtype.

The value corresponds to whether applying thePATH expression to the row pattern yields any values.

The specifiedtype should have a cast from theboolean type.

Optionally, you can useON ERROR to specify whether to throw the error or return the specified value when an error occurs during JSON path evaluation or when coercing SQL/JSON value to the specified type. The default is to return a boolean valueFALSE.

NESTED [ PATH]path_expression [ASjson_path_name]COLUMNS (json_table_column [, ...] )

Extracts SQL/JSON values from nested levels of the row pattern, generates one or more columns as defined by theCOLUMNS subclause, and inserts the extracted SQL/JSON values into those columns. Thejson_table_column expression in theCOLUMNS subclause uses the same syntax as in the parentCOLUMNS clause.

TheNESTED PATH syntax is recursive, so you can go down multiple nested levels by specifying severalNESTED PATH subclauses within each other. It allows to unnest the hierarchy of JSON objects and arrays in a single function invocation rather than chaining severalJSON_TABLE expressions in an SQL statement.

ASjson_path_name

The optionaljson_path_name serves as an identifier of the providedpath_expression. The name must be unique and distinct from the column names.

{ERROR |EMPTY }ON ERROR

The optionalON ERROR can be used to specify how to handle errors when evaluating the top-levelpath_expression. UseERROR if you want the errors to be thrown andEMPTY to return an empty table, that is, a table containing 0 rows. Note that this clause does not affect the errors that occur when evaluating columns, for which the behavior depends on whether theON ERROR clause is specified against a given column.

Examples

In the examples that follow, the following table containing JSON data will be used:

CREATE TABLE my_films ( js jsonb );INSERT INTO my_films VALUES ('{ "favorites" : [   { "kind" : "comedy", "films" : [     { "title" : "Bananas",       "director" : "Woody Allen"},     { "title" : "The Dinner Game",       "director" : "Francis Veber" } ] },   { "kind" : "horror", "films" : [     { "title" : "Psycho",       "director" : "Alfred Hitchcock" } ] },   { "kind" : "thriller", "films" : [     { "title" : "Vertigo",       "director" : "Alfred Hitchcock" } ] },   { "kind" : "drama", "films" : [     { "title" : "Yojimbo",       "director" : "Akira Kurosawa" } ] }  ] }');

The following query shows how to useJSON_TABLE to turn the JSON objects in themy_films table to a view containing columns for the keyskind,title, anddirector contained in the original JSON along with an ordinality column:

SELECT jt.* FROM my_films, JSON_TABLE (js, '$.favorites[*]' COLUMNS (   id FOR ORDINALITY,   kind text PATH '$.kind',   title text PATH '$.films[*].title' WITH WRAPPER,   director text PATH '$.films[*].director' WITH WRAPPER)) AS jt;

 id |   kind   |             title              |             director----+----------+--------------------------------+----------------------------------  1 | comedy   | ["Bananas", "The Dinner Game"] | ["Woody Allen", "Francis Veber"]  2 | horror   | ["Psycho"]                     | ["Alfred Hitchcock"]  3 | thriller | ["Vertigo"]                    | ["Alfred Hitchcock"]  4 | drama    | ["Yojimbo"]                    | ["Akira Kurosawa"](4 rows)

The following is a modified version of the above query to show the usage ofPASSING arguments in the filter specified in the top-level JSON path expression and the various options for the individual columns:

SELECT jt.* FROM my_films, JSON_TABLE (js, '$.favorites[*] ? (@.films[*].director == $filter)'   PASSING 'Alfred Hitchcock' AS filter     COLUMNS (     id FOR ORDINALITY,     kind text PATH '$.kind',     title text FORMAT JSON PATH '$.films[*].title' OMIT QUOTES,     director text PATH '$.films[*].director' KEEP QUOTES)) AS jt;

 id |   kind   |  title  |      director----+----------+---------+--------------------  1 | horror   | Psycho  | "Alfred Hitchcock"  2 | thriller | Vertigo | "Alfred Hitchcock"(2 rows)

The following is a modified version of the above query to show the usage ofNESTED PATH for populating title and director columns, illustrating how they are joined to the parent columns id and kind:

SELECT jt.* FROM my_films, JSON_TABLE ( js, '$.favorites[*] ? (@.films[*].director == $filter)'   PASSING 'Alfred Hitchcock' AS filter   COLUMNS (    id FOR ORDINALITY,    kind text PATH '$.kind',    NESTED PATH '$.films[*]' COLUMNS (      title text FORMAT JSON PATH '$.title' OMIT QUOTES,      director text PATH '$.director' KEEP QUOTES))) AS jt;

 id |   kind   |  title  |      director----+----------+---------+--------------------  1 | horror   | Psycho  | "Alfred Hitchcock"  2 | thriller | Vertigo | "Alfred Hitchcock"(2 rows)

The following is the same query but without the filter in the root path:

SELECT jt.* FROM my_films, JSON_TABLE ( js, '$.favorites[*]'   COLUMNS (    id FOR ORDINALITY,    kind text PATH '$.kind',    NESTED PATH '$.films[*]' COLUMNS (      title text FORMAT JSON PATH '$.title' OMIT QUOTES,      director text PATH '$.director' KEEP QUOTES))) AS jt;

 id |   kind   |      title      |      director----+----------+-----------------+--------------------  1 | comedy   | Bananas         | "Woody Allen"  1 | comedy   | The Dinner Game | "Francis Veber"  2 | horror   | Psycho          | "Alfred Hitchcock"  3 | thriller | Vertigo         | "Alfred Hitchcock"  4 | drama    | Yojimbo         | "Akira Kurosawa"(5 rows)

The following shows another query using a differentJSON object as input. It shows the UNION "sibling join" betweenNESTED paths$.movies[*] and$.books[*] and also the usage ofFOR ORDINALITY column atNESTED levels (columnsmovie_id,book_id, andauthor_id):

SELECT * FROM JSON_TABLE ('{"favorites":    [{"movies":      [{"name": "One", "director": "John Doe"},       {"name": "Two", "director": "Don Joe"}],     "books":      [{"name": "Mystery", "authors": [{"name": "Brown Dan"}]},       {"name": "Wonder", "authors": [{"name": "Jun Murakami"}, {"name":"Craig Doe"}]}]}]}'::json, '$.favorites[*]'COLUMNS (  user_id FOR ORDINALITY,  NESTED '$.movies[*]'    COLUMNS (    movie_id FOR ORDINALITY,    mname text PATH '$.name',    director text),  NESTED '$.books[*]'    COLUMNS (      book_id FOR ORDINALITY,      bname text PATH '$.name',      NESTED '$.authors[*]'        COLUMNS (          author_id FOR ORDINALITY,          author_name text PATH '$.name'))));

 user_id | movie_id | mname | director | book_id |  bname  | author_id | author_name---------+----------+-------+----------+---------+---------+-----------+--------------       1 |        1 | One   | John Doe |         |         |           |       1 |        2 | Two   | Don Joe  |         |         |           |       1 |          |       |          |       1 | Mystery |         1 | Brown Dan       1 |          |       |          |       2 | Wonder  |         1 | Jun Murakami       1 |          |       |          |       2 | Wonder  |         2 | Craig Doe(5 rows)


Prev Up Next
9.15. XML Functions Home 9.17. Sequence Manipulation Functions
pdfepub
Go to PostgreSQL 17
By continuing to browse this website, you agree to the use of cookies. Go toPrivacy Policy.

[8]ページ先頭

©2009-2025 Movatter.jp