How to get ResultSetMetaData in ClickHousePreparedStatement

[suhli]

Is there any way to get the result set metadata without execution like issue #235 ?
I check codes main branch, seems like the reference file change ClickHousePreparedStatementImpl.java with PR #288 has been deprecated

[zhicwu]

Hi @suhli, could you share the use case? Did you mean ParameterMetaData?

[suhli]

Hi @suhli, could you share the use case? Did you mean ParameterMetaData?

I'm using Trino as middleware provides the ability to query across different databases.
Yet in some cases, I need to pass the original sql to downstream databases. eg: some json query(Trino will not pushdown filter in some case)
I found the following comments in Trino clickhouse plugin testcase that describe the reason(it has been delete in main branch,yet still not support):

// table function disabled for ClickHouse, because it doesn't provide ResultSetMetaData, so the result relation type cannot be determined

support native

reason

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To be exact,what they need is ResultSetMetaData in PrepareStatement before query execution.
source

[zhicwu]

Thank you for the additional context. Since this is for a push-down query, it would not be ideal to execute the full query just to retrieve the ResultSetMetaData for type inference. Actually I'm also concerned about when to release ResultSet in the original fix. Anyway, as an optimization, we could usedesc (<original query>) instead. I'll fix this tonight along with other minor issues.