working on json_path_exists

[valkrypton]

@weiznich I was trying to implement the jsonb_path_exists function. One of its argument is of type Jsonpath. Currently there is no such type in diesel, so I tried to implement it using the jsonpath_rust crate.

I implemented the FromSql trait for it, but I could not figure out how to implement the ToSql trait. I'd appreciate if you could take a look and help me with this or maybe i am going completely in the wrong direction with this?

[weiznich]

Thanks for working on this. The FromSql implementation needs to read the binary representation of a json path as defined in the PostgreSQL protocol. Unfortunately the documentation of that format is mostly not existing, at least for anything that's not a trivial type. That means you likely need to perform some experimentation. One possibility would be to just setup a test case that loads a jsonpath value from the database and inspect the output. That should tell us how postgres serializes these data. Hopefully that's just the path as string or something simple like that. The other way is to dig through the postgres source code and find something there. This file might be a starting point.