On Sat, 22 Jan 2022 at 22:00, Tom Lane <t...@sss.pgh.pa.us> wrote: > Erwin Brandstetter <brsaw...@gmail.com> writes: > > On Sat, 22 Jan 2022 at 20:31, David G. Johnston < > david.g.johns...@gmail.com> > > wrote: > >> 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, > > "Without any additional processing" is the key restriction there. > > > 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. > > It is documented --- you just quoted the text that does so. > > I don't have a lot of sympathy for "JSON-reading" code that fails to > conform to the JSON RFC, so I'm disinclined to work harder than that. > > I suggest to clarify the behavior of json_strip_nulls() in the manual: that it also strips insignificant white space. If that may change in future versions, also say so. People are starting to use json_strip_nulls() for the purpose (and may regret it later): https://stackoverflow.com/questions/27505181/fetching-compact-version-of-jsonb-in-postgresql/56842519#56842519
If (like I assume) json_strip_nulls() should not be relied upon to strip whitespace, it would be great to have a separate, dedicated function for that. That's independent from the first suggestion. Regards Erwin
