json_strip_nulls()

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От	Erwin Brandstetter
Тема	json_strip_nulls()
Дата	22 января 2022 г. 22:10:46
Msg-id	CAGHENJ5OckBWa22Cf=N9e68EZM2=_S8AWjWF-_xnGa+iktUh7g@mail.gmail.com обсуждение исходный текст
Ответы	Re: json_strip_nulls() ("David G. Johnston" <david.g.johnston@gmail.com>)
Список	pgsql-docs

Дерево обсуждения

The manual says this about json_strip_nulls()[1]:

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

[1] https://www.postgresql.org/docs/current/functions-json.html#FUNCTIONS-JSON-PROCESSING-TABLE

But the function also strips all insignificant white space:

test=> SELECT json_strip_nulls(json '{"a": 1 ,
test'> "foo" : "bar"
test'> }');
json_strip_nulls
---------------------
{"a":1,"foo":"bar"}

This is a useful feature to trim noise from json values, but unreliable while undocumented. So let's document the behavior:

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 additionally removes all insignificant white space.

If that's undesirable, let's remove the functionality - and provide a dedicated function for the task.

I found similar (unresolved) considerations here:

https://www.postgresql.org/message-id/20160610110633.GG18838%40zip.com.au

There were related requests on Stackoverflow:

- https://stackoverflow.com/questions/27505181/fetching-compact-version-of-jsonb-in-postgresql

- https://stackoverflow.com/questions/70813106/jsonb-cast-to-text-without-sporious-spaces

Regards

Erwin

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