In talking to Wyatt Alt about PQL, he noted that PDB has a parser that complies PQL into the AST syntax. Exposing this functionality in an end point would be potentially useful in supporting structured facts for node group rules in the NC UI.
We have decided to add an optional query param to the root endpoint to indicate the desire to parse the PQL query into AST rather than query the database. For example: curl -X GET http://localhost:8080/pdb/query/v4 -d 'query=<some query>' -d 'parse_pql_only=true'