How call built-in functions in ClickHouse

[psharaev]

Recently I had to make such a query:

select count(distinct group_id) from clickhouse.public.testtable;

But he worked very slowly, because not the most optimal execution plan was drawn up for him:

trino> explain select count(distinct group_id) from clickhouse.public.testtable;
                                                                                            Query Plan
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Trino version: testversion
 Fragment 0 [SOURCE]
     Output layout: [_pfgnrtd]
     Output partitioning: SINGLE []
     Output[columnNames = [_col0]]
     │   Layout: [_pfgnrtd:bigint]
     │   Estimates: {rows: ? (?), cpu: 0, memory: 0B, network: 0B}
     │   _col0 := _pfgnrtd
     └─ TableScan[table = clickhouse:Query[SELECT count("group_id") AS "_pfgnrtd_0" FROM (SELECT "group_id" FROM "public"."testtable" GROUP BY "group_id") o] columns=[_pfgnrtd_0:bigint:bigint]]
            Layout: [_pfgnrtd:bigint]
            Estimates: {rows: ? (?), cpu: ?, memory: 0B, network: 0B}
            _pfgnrtd := _pfgnrtd_0:bigint:bigint


(1 row)

But ClickHouse has a large number of built-in functions. One of them will allow me to execute my query much faster, namely uniqExact. And I would like to execute the following query:

trino> select uniq(val) from clickhouse.public.testtable;
Query 20230412_132742_00029_e9aab failed: line 1:7: Function 'uniq' not registered
LINE 1: select uniqExact(group_id) from clickhouse.public.testtable

But trino doesn't know anything about this function. Can I somehow call the built-in functions in ClickHouse (and basically any other data source)?

I found in the documentation how to create my own functions, but as I understand it, they allow you to implement my logic, but in no way provide access to existing functions

[psharaev]

#1839 basically solves my problem

[ebyhr]

#1839 basically solves my problem

There's #16182 for ClickHouse connector.