ClickHouse dry run query

Question

I work on ClickHouse proxy which would validate and modify query before sending it to ClickHouse. To implement validation logic and I need to know what columns user request. The problem comes in when user uses * in select's.

For simple queries like select * from table I can expand * by myself and transform original query to e.g. select a,b,c from table.

Knowing table and column names and can check against user's permissions if he can access those columns. But how to deal with complicated queries with many join, subqueries etc. I was hoping that maybe there is functionality in ClickHouse which would allow to dry-run query before executing it, then ClickHouse would parse, analyze, optimize original SQL and produce expand one without *.

I couldn't find anything like that in ClickhHouse documentation. I use sqlglot library to transform AST. Any ideas how resolve my problem?

Thank you in advance

Answer 1

I asked someone working in ClickHouse. You can run EXPLAIN <query> in the ClickHouse, but not aware of such parser independently outside ClickHouse. As this results require the table schema definition.