Improve JSON documentation

[Thijs Damsma]

I am having difficulty using sqlalchemy to setup queries for JSON fields, specifically the issue I mentioned in the following stack-overflow question

Of course this is also a not so subtle attempt to draw some attention to my question, but more in general I found the documentation for using JSON/JSONB and sqlalchemy very limited. It would be of great help if there were some more examples for doing less trivial querying and manipulation

Thanks!

[Mike Bayer]

This seems like more of a request for Postgresql/JSON speciifc recipes using PG's special JSON functions. We dont have any specific support for these functions and #2450 indicates better support for some of these result types.

We're getting a lot of these fairly vague "improve docs for X" requests lately but I don't see any action to take here. func.FOO() is documented, how to select from func.FOO() as a FROM is documented (see http://docs.sqlalchemy.org/en/rel_1_0/core/tutorial.html#functions), but note that we aren't very good at PG's functions yet so once #2450 is done we'd have better docs for PG's functions overall.

[Mike Bayer]

take a look at the jsonb_each recipe at https://bitbucket.org/zzzeek/sqlalchemy/issues/3555/extract-a-records-field#comment-22608043 I made for someone. Selecting from these PG functions is roughly possible with SQLAlchemy but it isn't built in right now and requires building custom function and expression objects, and a comprehensive out-of-the-box solution does not exist right now. it needs to be implemented, which itself requires a very thorough survey of everything needed and that is a big job.

[Mike Bayer]

Duplicate of #3566.