query_typed still uses prepared statements sometimes, to get type info

[radix]

We are trying to use query_typed in an environment with pgcat -- we are using query_typed specifically because it avoids prepared statements, which we can't use with pgcat.

However, it seems that query_typed sometimes still uses prepared statements, if you trace the code where it calls get_type and then query::query. This is happening in a situation where we are trying to query a value that has a custom type (an enum that we've defined in postgres).

So, I think at the very least, this gotcha should probably be called out in query_typed's documentation, but I also wonder if it can be avoided by having get_type use query_typed instead of query? (I also see some code that is explicitly prepareing something in get_type too, I'm not sure if that's also about prepared statements - I have not spent a ton of time reading the code yet).

[sfackler]

We currently cache the prepared statements used for type retrieval. We could stop doing that and use query_typed - it'd probably the type lookups slightly slower but I'm assuming it would probably be unnoticeable in practice.