I have come across some missing documentation that I think could benefit the community.
Several functions like `jsonb_exists`, `jsonb_exists_any`, `jsonb_exists_all` have existed for many PG versions but were not documented. They are equivalent to `?`, `?|`, and `?&` operators. But some JDBC drivers have issues with native queries containing these operators (see https://stackoverflow.com/questions/38370972/how-do-i-use-postgresql-jsonb-operators-containing-a-question-mark-via-jdb), so it is useful for users of PG to know the function equivalents of these operators.
I have attached the patch as an attachment to this email. The documentation builds correctly without any lint errors after applying the patch locally. This is my first time contributing, so let me know if there is anything else I should do (add to commitfest etc).
I'm doubtful that encouraging use of these functions for JDBC-users is better than them learning to write queries using the proper operator. The reality is that the usage of indexes depends upon operators being used in query text, not function names (unless you define a functional index, which doesn't happen). Your SO post says as much and does mention that ?? is indeed the coding that is required.
What I think we should do in light of this reality, though, is indeed prohibit "??" as (or within) an operator in PostgreSQL. Since core is not presently using that operator its prohibition should be reasonably simple - though maybe extension authors got too creative?
-1 to this patch on the above grounds. As for the patch itself:
The parentheticals you wrote might be appropriate for a commit message but do not belong in the documentation. Mentioning JDBC is simply a no-no; and we don't document "why" we decided to document something. We also don't go around pointing out what functions and operators perform the same behavior (mostly because we generally just don't do that, see above).
I didn't actually review the material parts of the table. Nothing seems obviously incorrect there though.
