On Sat, 22 Jan 2022 at 20:31, David G. Johnston <david.g.johns...@gmail.com> wrote:
> On Sat, Jan 22, 2022 at 12:11 PM Erwin Brandstetter <brsaw...@gmail.com> > wrote: > >> But the function also strips all insignificant white space: >> [...] >> This is a useful feature to trim noise from json values, but unreliable >> while undocumented. So let's document the behavior: >> > > json_strip_nulls doesn't make any promise regarding its output json other > than that it is valid. Since we are munging the json we are arguably > within our rights to output whatever transformed version we want. The > format should not be documented. > Within our rights, maybe. The manual makes related promises[1]: > Because the json type stores an exact copy of the input text, it will preserve semantically-insignificant white space between tokens And[2]: > As previously stated, when a JSON value is input and then printed without any additional processing, json outputs the same text that was input, Not strictly contradicting, but the current behavior of json_strip_nulls() is still surprising. Either the input should be preserved as far as possible or, failing that, the actual behavior documented. [1] https://www.postgresql.org/docs/current/datatype-json.html [2] https://www.postgresql.org/docs/current/datatype-json.html#JSON-KEYS-ELEMENTS > > >> >> If that's undesirable, let's remove the functionality - and provide a >> dedicated function for the task. >> > > I agree we should at least provide a function that takes a json or jsonb > and outputs its text representation in a minimalist form. > > I found similar (unresolved) considerations here: >> >> https://www.postgresql.org/message-id/20160610110633.GG18838%40zip.com.au >> >> > This whole situation went through a fairly lengthy discussion back in 2016: > > > https://www.postgresql.org/message-id/flat/CAH7T-ap6R_xzWz98c6AQzQuGsK_vpgr-et4VRaSjgxqom--ibw%40mail.gmail.com > > It's an interesting, and IMO, disappointing thread. Maybe we can do > better now and focus on one missing capability the community desires and > actually get something committed. > That would address the main issue here: to have a function doing that reliably. Regards Erwin
