Function try_plan_array_maint_fn 

pub fn try_plan_array_maint_fn(
    items: &[SelectItem],
    catalog: &dyn SqlCatalog,
) -> Result<Option<SqlPlan>>

Try to intercept a no-FROM SELECT array_flush(name) / SELECT array_compact(name). The single projection item must be a bare function call carrying one string-literal argument.