Postgraphile - "Query Root must be provided" error message - graphql

Question

We have an existing postgresql database with data and we are experimenting with postgraphile as a graphql API. We are running into an error that is leaving us scratching our head. the server runs fine but we get the following:
postgraphile -c postgres://username:password#localhost:5432/my_db
PostGraphile server listening on port 5000
‣ Connected to Postgres instance postgres://localhost:5432/my_db
‣ Introspected Postgres schema(s) public
‣ GraphQL endpoint served at http://localhost:5000/graphql
‣ GraphiQL endpoint served at http://localhost:5000/graphiql
* * *
An error occurred, it might be okay but it doesn't look like the error we were expecting... run with envvar 'DEBUG="graphile-build:warn"' to view the error
An error occurred, it might be okay but it doesn't look like the error we were expecting... run with envvar 'DEBUG="graphile-build:warn"' to view the error
Error: Query root type must be provided.
at assertValidSchema (C:\Users\user\AppData\Roaming\npm\node_modules\postgraphile\node_modules\graphql\type\validate.js:78:11)
at Object.validate (C:\Users\user\AppData\Roaming\npm\node_modules\postgraphile\node_modules\graphql\validation\validate.js:61:35)
at parseQuery (C:\Users\user\AppData\Roaming\npm\node_modules\postgraphile\build\postgraphile\http\createPostGraphileHttpRequestHandler.js:208:48)
at Promise.all.paramsList.map (C:\Users\user\AppData\Roaming\npm\node_modules\postgraphile\build\postgraphile\http\createPostGraphileHttpRequestHandler.js:469:63)
at Array.map (<anonymous>)
at requestHandler (C:\Users\user\AppData\Roaming\npm\node_modules\postgraphile\build\postgraphile\http\createPostGraphileHttpRequestHandler.js:435:52)
at <anonymous>
at process._tickCallback (internal/process/next_tick.js:188:7)
and when we navigate to localhost:500/graphiql we see a a "no schema available" in the documentation explorer.
is the query root the publicschema? or what are we missing?

Answer 1

Newer versions of PostGraphile have much more helpful error messages, often including a suggested solution. The "An error occurred" errors like those above now also contain a preview of the underlying error which helps with diagnosis.
There are instructions here on how to set the DEBUG environmental variable here: https://www.graphile.org/postgraphile/debugging/#debug-envvars
Here's how you might do it in Linux, macOS or Windows:
# Bash (Linux, macOS, etc)
export DEBUG="graphile-build:warn" postgraphile -c postgres://username:password#localhost:5432/my_db
# Windows Console
set DEBUG=graphile-build:warn & postgraphile -c postgres://username:password#localhost:5432/my_db
# Windows PowerShell
$env:DEBUG = "graphile-build:warn"; postgraphile -c postgres://username:password#localhost:5432/my_db