PostgreSQL 14 preview - 支持 jsonb 下标语法, 支持set原子操作, 类似array下标

作者

digoal

日期

2021-02-01

标签

PostgreSQL , jsonb , subscripting , 下标

背景

https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=676887a3b0b8e3c0348ac3f82ab0d16e9a24bd43
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=81fcc72e66222357f9bccce3eeda62eb2cb29849
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=aa6e46daf5304e8d9e66fefc1a5bd77622ec6402
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=7c5d57caed4d8af705d0cc3131d0d8ed72b7a41d

```
Implementation of subscripting for jsonb

Subscripting for jsonb does not support slices, does not have a limit for the
number of subscripts, and an assignment expects a replace value to have jsonb
type. There is also one functional difference between assignment via
subscripting and assignment via jsonb_set(). When an original jsonb container
is NULL, the subscripting replaces it with an empty jsonb and proceeds with
an assignment.

For the sake of code reuse, we rearrange some parts of jsonb functionality
to allow the usage of the same functions for jsonb_set and assign subscripting
operation.

The original idea belongs to Oleg Bartunov.

Catversion is bumped.
```

+-- jsonb subscript +select ('123'::jsonb)['a']; + jsonb +------- + +(1 row) + +select ('123'::jsonb)[0]; + jsonb +------- + +(1 row) + +select ('123'::jsonb)[NULL]; + jsonb +------- + +(1 row) + +select ('{"a": 1}'::jsonb)['a']; + jsonb +------- + 1 +(1 row) + +select ('{"a": 1}'::jsonb)[0]; + jsonb +------- + +(1 row) + +select ('{"a": 1}'::jsonb)['not_exist']; + jsonb +------- + +(1 row) + +select ('{"a": 1}'::jsonb)[NULL]; + jsonb +------- + +(1 row) + +select ('[1, "2", null]'::jsonb)['a']; + jsonb +------- + +(1 row) + +select ('[1, "2", null]'::jsonb)[0]; + jsonb +------- + 1 +(1 row) + +select ('[1, "2", null]'::jsonb)['1']; + jsonb +------- + "2" +(1 row) + +select ('[1, "2", null]'::jsonb)[1.0]; +ERROR: subscript type is not supported +LINE 1: select ('[1, "2", null]'::jsonb)[1.0]; + ^ +HINT: Jsonb subscript must be coerced to either integer or text +select ('[1, "2", null]'::jsonb)[2]; + jsonb +------- + null +(1 row) + +select ('[1, "2", null]'::jsonb)[3]; + jsonb +------- + +(1 row) + +select ('[1, "2", null]'::jsonb)[-2]; + jsonb +------- + "2" +(1 row) + +select ('[1, "2", null]'::jsonb)[1]['a']; + jsonb +------- + +(1 row) + +select ('[1, "2", null]'::jsonb)[1][0]; + jsonb +------- + +(1 row) + +select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['b']; + jsonb +------- + "c" +(1 row) + +select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d']; + jsonb +----------- + [1, 2, 3] +(1 row) + +select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d'][1]; + jsonb +------- + 2 +(1 row) + +select ('{"a": 1, "b": "c", "d": [1, 2, 3]}'::jsonb)['d']['a']; + jsonb +------- + +(1 row) + +select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1']; + jsonb +--------------- + {"a2": "aaa"} +(1 row) + +select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1']['a2']; + jsonb +------- + "aaa" +(1 row) + +select ('{"a": {"a1": {"a2": "aaa"}}, "b": "bbb", "c": "ccc"}'::jsonb)['a']['a1']['a2']['a3']; + jsonb +------- + +(1 row) + +select ('{"a": ["a1", {"b1": ["aaa", "bbb", "ccc"]}], "b": "bb"}'::jsonb)['a'][1]['b1']; + jsonb +----------------------- + ["aaa", "bbb", "ccc"] +(1 row) + +select ('{"a": ["a1", {"b1": ["aaa", "bbb", "ccc"]}], "b": "bb"}'::jsonb)['a'][1]['b1'][2]; + jsonb +------- + "ccc" +(1 row) + +-- slices are not supported +select ('{"a": 1}'::jsonb)['a':'b']; +ERROR: jsonb subscript does not support slices +LINE 1: select ('{"a": 1}'::jsonb)['a':'b']; + ^ +select ('[1, "2", null]'::jsonb)[1:2]; +ERROR: jsonb subscript does not support slices +LINE 1: select ('[1, "2", null]'::jsonb)[1:2]; + ^ +select ('[1, "2", null]'::jsonb)[:2]; +ERROR: jsonb subscript does not support slices +LINE 1: select ('[1, "2", null]'::jsonb)[:2]; + ^ +select ('[1, "2", null]'::jsonb)[1:]; +ERROR: jsonb subscript does not support slices +LINE 1: select ('[1, "2", null]'::jsonb)[1:]; + ^ +select ('[1, "2", null]'::jsonb)[:]; +ERROR: jsonb subscript does not support slices +create TEMP TABLE test_jsonb_subscript ( + id int, + test_json jsonb +); +insert into test_jsonb_subscript values +(1, '{}'), -- empty jsonb +(2, '{"key": "value"}'); -- jsonb with data +-- update empty jsonb +update test_jsonb_subscript set test_json['a'] = '1' where id = 1; +select * from test_jsonb_subscript; + id | test_json +----+------------------ + 2 | {"key": "value"} + 1 | {"a": 1} +(2 rows) + +-- update jsonb with some data +update test_jsonb_subscript set test_json['a'] = '1' where id = 2; +select * from test_jsonb_subscript; + id | test_json +----+-------------------------- + 1 | {"a": 1} + 2 | {"a": 1, "key": "value"} +(2 rows) + +-- replace jsonb +update test_jsonb_subscript set test_json['a'] = '"test"'; +select * from test_jsonb_subscript; + id | test_json +----+------------------------------- + 1 | {"a": "test"} + 2 | {"a": "test", "key": "value"} +(2 rows) + +-- replace by object +update test_jsonb_subscript set test_json['a'] = '{"b": 1}'::jsonb; +select * from test_jsonb_subscript; + id | test_json +----+--------------------------------- + 1 | {"a": {"b": 1}} + 2 | {"a": {"b": 1}, "key": "value"} +(2 rows) + +-- replace by array +update test_jsonb_subscript set test_json['a'] = '[1, 2, 3]'::jsonb; +select * from test_jsonb_subscript; + id | test_json +----+---------------------------------- + 1 | {"a": [1, 2, 3]} + 2 | {"a": [1, 2, 3], "key": "value"} +(2 rows) + +-- use jsonb subscription in where clause +select * from test_jsonb_subscript where test_json['key'] = '"value"'; + id | test_json +----+---------------------------------- + 2 | {"a": [1, 2, 3], "key": "value"} +(1 row) + +select * from test_jsonb_subscript where test_json['key_doesnt_exists'] = '"value"'; + id | test_json +----+----------- +(0 rows) + +select * from test_jsonb_subscript where test_json['key'] = '"wrong_value"'; + id | test_json +----+----------- +(0 rows) + +-- NULL +update test_jsonb_subscript set test_json[NULL] = '1'; +ERROR: jsonb subscript in assignment must not be null +update test_jsonb_subscript set test_json['another_key'] = NULL; +select * from test_jsonb_subscript; + id | test_json +----+------------------------------------------------------- + 1 | {"a": [1, 2, 3], "another_key": null} + 2 | {"a": [1, 2, 3], "key": "value", "another_key": null} +(2 rows) + +-- NULL as jsonb source +insert into test_jsonb_subscript values (3, NULL); +update test_jsonb_subscript set test_json['a'] = '1' where id = 3; +select * from test_jsonb_subscript; + id | test_json +----+------------------------------------------------------- + 1 | {"a": [1, 2, 3], "another_key": null} + 2 | {"a": [1, 2, 3], "key": "value", "another_key": null} + 3 | {"a": 1} +(3 rows) + +update test_jsonb_subscript set test_json = NULL where id = 3; +update test_jsonb_subscript set test_json[0] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+--------------------------------------------------------------- + 1 | {"0": 1, "a": [1, 2, 3], "another_key": null} + 2 | {"0": 1, "a": [1, 2, 3], "key": "value", "another_key": null} + 3 | [1] +(3 rows) +

+-- Fill the gaps logic +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '[0]'); +update test_jsonb_subscript set test_json[5] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+-------------------------------- + 1 | [0, null, null, null, null, 1] +(1 row) + +update test_jsonb_subscript set test_json[-4] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+----------------------------- + 1 | [0, null, 1, null, null, 1] +(1 row) + +update test_jsonb_subscript set test_json[-8] = '1'; +ERROR: path element at position 1 is out of range: -8 +select * from test_jsonb_subscript; + id | test_json +----+----------------------------- + 1 | [0, null, 1, null, null, 1] +(1 row) + +-- keep consistent values position +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '[]'); +update test_jsonb_subscript set test_json[5] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+----------------------------------- + 1 | [null, null, null, null, null, 1] +(1 row) + +-- create the whole path +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '{}'); +update test_jsonb_subscript set test_json['a'][0]['b'][0]['c'] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+---------------------------- + 1 | {"a": [{"b": [{"c": 1}]}]} +(1 row) + +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '{}'); +update test_jsonb_subscript set test_json['a'][2]['b'][2]['c'][2] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+------------------------------------------------------------------ + 1 | {"a": [null, null, {"b": [null, null, {"c": [null, null, 1]}]}]} +(1 row) + +-- create the whole path with already existing keys +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '{"b": 1}'); +update test_jsonb_subscript set test_json['a'][0] = '2'; +select * from test_jsonb_subscript; + id | test_json +----+-------------------- + 1 | {"a": [2], "b": 1} +(1 row) + +-- the start jsonb is an object, first subscript is treated as a key +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '{}'); +update test_jsonb_subscript set test_json[0]['a'] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+----------------- + 1 | {"0": {"a": 1}} +(1 row) + +-- the start jsonb is an array +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '[]'); +update test_jsonb_subscript set test_json[0]['a'] = '1'; +update test_jsonb_subscript set test_json[2]['b'] = '2'; +select * from test_jsonb_subscript; + id | test_json +----+---------------------------- + 1 | [{"a": 1}, null, {"b": 2}] +(1 row) + +-- overwriting an existing path +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '{}'); +update test_jsonb_subscript set test_json['a']['b'][1] = '1'; +update test_jsonb_subscript set test_json['a']['b'][10] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+---------------------------------------------------------------------------- + 1 | {"a": {"b": [null, 1, null, null, null, null, null, null, null, null, 1]}} +(1 row) + +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '[]'); +update test_jsonb_subscript set test_json[0][0][0] = '1'; +update test_jsonb_subscript set test_json[0][0][1] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+------------ + 1 | [[[1, 1]]] +(1 row) + +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '{}'); +update test_jsonb_subscript set test_json['a']['b'][10] = '1'; +update test_jsonb_subscript set test_json['a'][10][10] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+------------------------------------------------------------------------------------------------------------------------------------------------------ + 1 | {"a": {"b": [null, null, null, null, null, null, null, null, null, null, 1], "10": [null, null, null, null, null, null, null, null, null, null, 1]}} +(1 row) + +-- an empty sub element +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '{"a": {}}'); +update test_jsonb_subscript set test_json['a']['b']['c'][2] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+-------------------------------------- + 1 | {"a": {"b": {"c": [null, null, 1]}}} +(1 row) + +delete from test_jsonb_subscript; +insert into test_jsonb_subscript values (1, '{"a": []}'); +update test_jsonb_subscript set test_json['a'][1]['c'][2] = '1'; +select * from test_jsonb_subscript; + id | test_json +----+--------------------------------------- + 1 | {"a": [null, {"c": [null, null, 1]}]} +(1 row) +

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