While working on a Drill plugin, Calcite unparsed a JdbcRel node and produced the following PostgreSQL query
The query fails due to a parsing exception, the reason is that the STRPOS function name is quoted using double quotes. I tried the query manually without quoting the function name and it executed successfully.
Drill uses Calcite v1.4 but as I compared it with the master branch, I found them identical.
I haven't tried that with custom functions yet.