postgres explain feature fails for queries with unreferenced parameters

[ashanbrown]

The postgres explain feature appears to depend on being able to infer a type for every parameter when generating the prepared statement. I'm seeing this problem in an environment where hasura is generating queries and the first parameter of a quey sent to postgres is just some metadata that is ignored. In the postgres logs this looks like:

DETAIL:  parameters: $1 = '{"x-hasura-role":"admin"}', ...

Parameter $1 is not referenced at all in the query.

I suspect the solution is to explicitly provide some known type for any unreferenced parameters in the "PREPARE" statement. Alternatively, the query parameters could be renumbered, filling unreferenced parameter position, but this could have the effect of making the original query less recognizable.

Describe the results you received:

Postgres logs show this when generating the prepared statement:

ERROR:  could not determine data type of parameter $1

Describe the results you expected:
I'd like to be able to see explain results for these queries.